MOBILE COMPUTING

VI – SEMESTER

BSC COMPURER SCIENCE

INTRODUCTION

Mobile Computing
Wireless MAMobile Computing vs Wireless Networking
Mobile Computing Applications
Characteristics of Mobile Computing
Structure Computing ApplicationC MAC Protocols
of Mobile Issues
Fixed Assignment Schemes
Random Assignment Schemes
Reservation based Schemes

MOBILE INTERNET PROTOCOL AND TRANSPORT LAYER

Overview of Mobile IP
Features of Mobile IP
Key Mechanism in Mobile IP
Route Optimization
Overview of TCP / IP
Architecture of TCP/IP
Adaptation of TCP / IP Window
Improvement in TCP Performance

MOBILE TELECOMMUNICATION SYSTEM

Global System for Mobile Communication

General Packet Radio Service
Universal Mobile Telecommunication System

MOBILE AD HOC NETWORKS

Adhoc Basic Concepts

Characteristics of Mobile ADHOC Networks
Applications of Mobile ADHOC Networks
Design Issues - Mobile ADHOC Networks
Routing - Mobile Adhoc Networks
Essential of Traditional Routing Protocols
Popular Routing Protocols
Vehicular Ad-Hoc Networks(VANET)
MANET vs VANET
Security in Mobile ADHOC Networks

MOBILE PLATFORMS AND APPLICATIONS

Mobile Device Operating Systems

Special Constraints and Requirements
Commercial Mobile Operating System
Software development kit:iOS,Android,Blackberry,Windows Phone
M-Commerce
Structure of M-Commerce
Pros and Cons of M-Commerce
Mobile Payment System and Security Issues
 UNIT - I

MOBILE COMPUTING

Mobile Computing is a technology that allows transmission of data, voice and

video via a computer or any other wireless enabled device without having to be
connected to a fixed physical link.
Mobile Computing is the use of portable computing devices (such as laptop and
handheld computers) in conjunction with mobile communications technologies to
enable users to access the Internet and data on their home or work computers from
anywhere in the world.
It is the process of computation on a mobile device. In mobile computing, a set
of distributed computing systems or service provider servers participate, connect, and
synchronise through mobile communication protocols.
Mobile computing is a generic term describing ability to use the technology to
wirelessly connect to and use centrally located information and/or application software
through the application of small, portable, and wireless computing and communication
devices. It provides decentralized (distributed) computations on diversified devices,
systems, and networks, which are mobile, synchronized, and interconnected via
mobile communication standards and protocols. Mobile device does not restrict itself
to just one
Application, such as, voice communication.
The main concept involves −
1.Mobile communication
2.Mobile hardware
3. Mobile software

Mobile communication
The mobile communication in this case, refers to the infrastructure put in place to
ensure that seamless and reliable communication goes on. These would include
devices such as protocols, services, bandwidth, and portals necessary to facilitate and
support the stated services. The data format is also defined at this stage. This ensures
that there is no collision with other existing systems which offer the same service.

Since the media is unguided / unbounded, the overlaying infrastructure is

basically radio wave-oriented. That is, the signals are carried over the air to
intended devices that are capable of receiving and sending similar kinds of signals.
Mobile Hardware
Mobile hardware includes mobile devices or device components that receive or
access the service of mobility. They would range from portable laptops, smart phones,
tablet Pc's, Personal Digital Assistants.

These devices will have a receptor medium that is capable of sensing and receiving
signals. These devices are configured to operate in full- duplex, whereby they are
capable of sending and receiving signals at the same time.
They don't have to wait until one device has finished communicating for the other
device to initiate communications. Above mentioned devices use an existing and
established network to operate on. In most cases, it would be a wireless network.
Mobile software
 Mobile software is the actual program that runs on the mobile hardware. It deals
with the characteristics and requirements of mobile applications. This is the engine of
the mobile device. In other terms, it is the operating system of the appliance. It's the
essential component that operates the mobile device.

Since portability is the main factor, this type of computing ensures that users
are not tied or pinned to a single physical location, but are able to operate from
anywhere. It incorporates all aspects of wireless communications.
Evolution of Mobile Computing
In today's computing world, different technologies have emerged. These have
grown to support the existing computer networks all over the world. With mobile
computing, we find that the need to be confined within one physical location has been
eradicated. We hear of terms such as telecommuting, which is being able to work from
home or the field but at the same time accessing resources as if one is in the office.
The advent of portable computers and laptops, Personal Digital Assistants (PDA),
PC tablets and smart phones, has in turn made mobile computing very convenient. The
portability of these devices ensure and enable the users to access all services as if they
were in the internal network of their company. For example, the use of Tablet PC and
iPads. This new technology enables the users to update documents, surf the internet,
send and receive e-mail, stream live video files, take photographs and also support
video and voice conferencing.
The constant and ever increasing demand for superior and robust smart devices has
been a catalyst for market share. Each manufacturer is trying to carve a niche for
himself in the market. These devices are invented and innovated to provide state-of-
the-art applications and services. For instance, different manufacturers of cellular
phones have come up with unique smart phones that are capable of performing the
same task as computers and at the same processing speed.
The market share for different competitors is constantly being fought for. For
example, the manufacturers of Apple's iPhone OS, Google's Android' Microsoft
Windows Mobile, Research In Motion's Blackberry OS, are constantly competing to
offer better products with each release.

The need for better, portable, affordable, and robust technology has made these
vendors to constantly be innovative. Market figure and statistics show an ever growing
need to purchase and use such devices for either professional or personal use. It is in
this light that services to suit long-term implementation are developed or innovated. It
has also pushed other industry vendors to adopt services that will provide better
services.
For example, cellular service providers are forced to improve and be innovative to
capture more subscribers. This can be in terms of superior services such as high speed
internet and data access, voice and video service etc. Hence the adoption of different
generations of networks like of 2G, 2.5G, 3G, 4G network services.

The essence of mobile computing is to be able to work from any location. The use
of iPads, tablets, smart phones, and notebooks have pushed the demand for these
devices. Modern day workers have such devices that enable them to carry out their
work from the confines of their own location. These devices are configured to access
and store large amounts of vital data.
Executive and top management can take decisions based on ready information
without going to the office. For example, sales reports and market forecasts can be
accessed through these devices or a meeting can take place via video or audio
conferencing through these devices. With such features being high in demand,
manufacturers are constantly coming up with applications geared to support different
services in terms of mobile computing.
 Advantages of Mobile Computing
Location Flexibility
This has enabled users to work from anywhere as long as there is a connection
established. A user can work without being in a fixed position. Their mobility ensures
that they are able to carry out numerous tasks at the same time and perform their stated
jobs.
Saves Time
The time consumed or wasted while travelling from different locations or to the
office and back, has been slashed. One can now access all the important documents
and files over a secure channel or portal and work as if they were on their computer. It
has enhanced telecommuting in many companies. It has also reduced unnecessary
incurred expenses.
Enhanced Productivity
Users can work efficiently and effectively from whichever location they find
comfortable. This in turn enhances their productivity level.
Ease of Research
Research has been made easier, since users earlier were required to go to the field
and search for facts and feed them back into the system. It has also made it easier for
field officers and researchers to collect and feed data from wherever they are without
making unnecessary trips to and from the office to the field.
Entertainment
Video and audio recordings can now be streamed on-the-go using mobile
computing. It's easy to access a wide variety of movies, educational and
informative material. With the improvement and availability of high speed data
connections at considerable cost, one is able to get all the entertainment they want
as they browse the internet for streamed data. One is able to watch news, movies,
and documentaries among other entertainment offers over the internet. This was not
possible before mobile computing dawned on the computing world.
Streamlining of Business Processes
Business processes are now easily available through secured connections.
Looking into security issues, adequate measures have been put in place to ensure
authentication and authorization of the user accessing the services.
Some business functions can be run over secure links and sharing of information
between business partners can also take place. Meetings, seminars and other
informative services can be conducted using video and voice conferencing. Travel
time and expenditure is also considerably reduced.
Disadvantages of Mobile Computing
Quality of Connectivity
One of the disadvantages is that the mobile devices will need either WiFi
connectivity or mobile network connectivity such as GPRS, 3G and in some countries
even 4G connectivity that is why this is a disadvantage because if you are not near any
of these connections your access to the internet is very limited.
Security Concerns
Mobile VPNs are unsafe to connect to, and also syncing devices might also lead
to security concerns. accessing a WiFi network can also be risky because WPA and
WEP security can be bypassed easily.
Power Consumption
Due to the use of batteries in these devices, these do not tend to last long, if in a
situation where there is no source of power for charging then that will certainly be a let
down.

MOBILE COMPUTING Vs WIRELESS NETWORKING

The terms "mobile" and "wireless" are often used interchangeably but in reality,
they are two very different concepts applied to modern computing and technology.
 Mobile is a word that is commonly used to describe portable devices. A mobile
device is one that is made to be taken anywhere. Therefore, it needs an internal battery
for power, and must be connected to a modern mobile network that can help it to send
and receive data without attaching to a hardware infrastructure.
Wireless, on the other hand, does not mean mobile. Traditional computers or other
non-mobile devices can access wireless networks. One very common example is the
use of a localized browser product in a local area network (LAN), where the router
takes what used to be a cabled interaction and makes it wireless. Other kinds of
wireless networks called wide area networks (WAN) can even use
components of 3G or 4G wireless systems made specifically for mobile
devices, but that doesn‘t mean that the devices on these networks are mobile. They
may still be plugged in or require proximity to a router or network node.
Mobile and wireless systems really accomplish two very different things. While a
wireless system provides a fixed or portable endpoint with access to a distributed
network, a mobile system offers all of the resources of that distributed network to
something that can go anywhere, barring any issues with local reception or technical
area coverage.
For another example of the difference between mobile and wireless, think of
businesses that offer Wi-Fi hotspots. A Wi-Fi hotspot is typically a resource for
someone who has a relatively fixed device, such as a laptop computer that doesn‘t
have its own internal Internet access built in. By contrast, mobile devices already have
inherent access to the Internet or other wireless systems through those cell tower
networks that ISPs and telecom companies built specifically for them. So mobile
devices don‘t need Wi-Fi - they already have their connections.
To some who are used to using both wireless and mobile networks, this distinction
may seem very simple. However, the difference between providing mobile and
wireless is likely to be something that gets explored more as new technologies
continue to develop, and companies continue to offer more different kinds of
interfaces to consumers.
Mobile is subgroup from wireless. We have wireless systems that are not mobile
and we have technologies which are wireless but not mobile in sense of technologies
deployed in mobile operators networks. We have fixed wireless (e.g. fixed WiMAX)
and e.g. TETRA which is not technology deployed in mobile (operators) networks.
In communication engineering, wireless communication(both static and dynamic) is
communication between Nodes/system without use of direct physical connection
rather it is through a non conducting or dielectric media. Where as in mobile
communication, communicating nodes moves within specified area and method of
communication is wireless communication suitably..e.g.-Mobile Ad-hoc networks
(MANETs).
 Wireless Communication in itself is a very broad concept that is achieved using
various inter-related technologies. Mobile Communication utilizes some of the
technologies that are made available / possible by Wireless Communication. Some of
the popular wireless technologies employed in Mobile Communication include: GPRS
(General Packet Radio Service), LTE (Long Term Evolution), HSPA (High Speed
Packet Access), GSM (Global System for Mobile Communication), EDGE (Enhanced
Data GSM Environment), CDMA (Code Division Multiple Access) and its variants,
etc.
Wireless refers to the method of transferring information between
a computing device, such as a personal data assistant (PDA), and a data source, such
as an agency database server, without a physical connection. However, not all wireless
communications technologies are created equally, offer the same uses or are even
mobile.
Mobile computing refers to computing devices that are not restricted to a desktop.
A mobile device may be a PDA, a smart phone or a web phone, a laptop computer,
or any one of numerous other devices that allow the user to complete tasks without
being tethered, or connected, to a network. Mobile computing does not necessarily
require wireless communication. In fact, it may not require communication between
devices at all.
Wireless communication is simply data communication without the use of a landline.
This may involve a cellular telephone, a two way radio, a fixed wireless connection, a
laser, or satellite communications. Here the computing device is continuously
connected to the base network.
Mobile computing essentially refers to a device that is not always connected to a
central network. This group of devices includes laptops, newly created smart phones
and also PDA's. These products may communicate with a base location, with or
without, a wireless connection

MOBILE COMPUTING APPLICATIONS

For Estate Agents

Estate agents can work either at home or out in the field. With
mobile computers they can be more productive. They can obtain current real estate
information by accessing multiple listing services, which they can do from home,
office or car when out with clients. They can provide clients with immediate feedback
regarding specific homes or neighbourhoods, and with faster loan approvals, since
applications can be submitted on the spot. Therefore, mobile computers allow them to
devote more time to clients.
Emergency Services
Ability to receive information on the move is vital where the emergency services are
involved. Information regarding the address, type and other details of an incident can
be dispatched quickly, via a CDPD system using mobile computers, to one or several
appropriate mobile units which are in the vicinity of the incident. Here the reliability
and security implemented in the CDPD system would be of great advantage.

In courts
Defence counsels can take mobile computers in court. When the opposing counsel
references a case which they are not familiar, they can use the computer to get direct,
real-time access to on-line legal database services, where they can gather information
on the case and related precedents. Therefore mobile computers allow immediate
access to a wealth of information, making people better informed and prepared.
In companies
Managers can use mobile computers in, say, critical presentations to major
customers. They can access the latest market share information. At a small recess, they
can revise the presentation to take advantage of this information. They can
communicate with the office about possible new offers and call meetings for
discussing responds to the new proposals. Therefore, mobile computers can leverage
competitive advantages.
Stock Information Collation/Control
In environments where access to stock is very limited i.e.: factory warehouses. The
use of small portable electronic databases accessed via a mobile computer would be
ideal. Data collated could be directly written to a central database, via a CDPD
network, which holds all stock information hence the need for transfer of data to the
central computer at a later date is not necessary. This ensures that from the time that a
stock count is completed, there is no inconsistency between the data input on the
portable computers and the central database.
Credit Card Verification
At Point of Sale (POS) terminals in shops and supermarkets, when customers use
credit cards for transactions, the intercommunication required between the bank
central computer and the POS terminal, in order to effect verification of the card
usage, can take place quickly and securely over cellular channels using a mobile
computer unit. This can speed up the transaction process and relieve congestion at the
POS terminals.
Taxi/Truck Dispatch
Using the idea of a centrally controlled dispatcher with several mobile units (taxis),
mobile computing allows the taxis to be given full details of the dispatched job as well
as allowing the taxis to communicate information about their whereabouts back to the
central dispatch office. This system is also extremely useful in secure deliveries ie:
Securicor. This allows a central computer to be able to track and receive status
information from all of its mobile secure delivery vans. Again, the security and
reliability properties of the CDPD system shine through.
Electronic Mail/Paging
Usage of a mobile unit to send and read emails is a very useful asset for any
business individual, as it allows him/her to keep in touch with any colleagues as well
as any urgent developments that may affect their work. Access to the Internet, using
mobile computing technology, allows the individual to have vast arrays of knowledge
at his/her fingertips. Paging is also achievable here, giving even more
intercommunication capability between individuals, using a single mobile computer
device.

CHARACTERISTICS OF MOBILE COMPUTING

1. Portability - The Ability to move a device within a learning environment or to
different environments with ease.
2. Social Interactivity - The ability to share data and collaboration between users.
3. Context Sensitivity - The ability to gather and respond to real or simulated data
unique to a current location, environment, or time.
4. Connectivity - The ability to be digitally connected for the purpose of
communication of data in any environment.
5. Individual - The ability to use the technology to provide scaffolding on difficult
activities and lesson customization for individual learners.
6. Small Size - Mobile devices are also known as handhelds, palmtops and smart
phones due to their roughly phone-like dimensions. A typical mobile device will fit in
the average adult's hand or pocket. Some mobile devices may fold or slide from a
compact, portable mode to a slightly larger size, revealing built-in keyboards or larger
screens. Mobile devices make use of touch screens and small keypads to receive input,
maintaining their small size and independence from external interface devices. The
standard form of a mobile device allows the user to operate it with one hand, holding
the device in the palm or fingers while executing its functions with the thumb.
Netbooks and small tablet computers are sometimes mistaken for true mobile devices,
based on their similarity in form and function, but if the device's size prohibits one-
handed operation or hinders portability, then it cannot be considered a true mobile
device.
7. Wireless Communication - Mobile devices are typically capable of
communication with other similar devices, with stationary computers and systems,
with networks and portable phones. Base mobile devices are capable of accessing the
Internet through Bluetooth or Wi-Fi networks, and many models are equipped to
access cell phone and wireless data networks as well. Email and texting are standard
ways of communicating with mobile devices, although many are also capable of
telephony, and some specialized mobile devices, such as RFID and barcode.
STRUCTURE OF MOBILE COMPUTING APPLICATION

Programming languages are used for mobile system software. Operating system
functions to run the software components onto the hardware. Middleware components
deployment. Layered structure arrangement of mobile computing components is used.
Protocols and layers are used for transmission and reception.
Programming Languages
The following are the programming languages used for Mobile Computing
applications are:
 Java - J2SE.
 J2ME (Java2 Micro edition)
 JavaCard (Java for smart card)
 The Java enterprise edition (J2EE) used for web and enterprise server based
applications of mobile services
 C and C++
 Visual C++
 Visual Basic
Operating System
Symbian OS, Window CE, Mac OS are the operating systems used in Mobile
computing applications. It offers the user to run an application without considering
the hardware specifications and functionalities. It provides functions which are used
for scheduling the multiple tasks in a system.
It provides the functions required for the synchronization of multiple tasks in the
system. It uses multiple threads synchronization and priority allocation. Management
functions (such as creation, activation, deletion, suspension, and delay) are used for
tasks and memory. It provides Interfaces for communication between software
components at the application layer, middleware layers, and hardware devices.
It facilitates the execution of software components on diversified hardware. It
provides Configurable libraries for the GUI (graphic user interface) in the device. It
provides.User application‘s GUIs, VUI (voice user interface) components, and phone
API. It provides the device drivers for the keyboard, display, USB, and other devices.
Middleware
Software components that link the application components with the network-
distributed components. It is used to discover the nearby device such as Bluetooth. It
is used to discover the nearby hot spot for achieving device synchronization with the
server or an enterprise server. It is used for retrieving data (which may be in Oracle or
DB2) from a network database. It is used for service discovery at network. It is used
for adaptation of the application to the platform and service availability.
Architecture of Mobile Computing Applications
Client/server architecture (and its variants) is often adopted for this kind of
applications. However we have to take into consideration some specific aspects
related to the mobile devices (clients), and their connectivity with servers.
Clients
There are many mobile device types, including RIM devices, cellular telephones,
PDAs, Tablet, PCs, and Laptop PCs. These mobile devices can typically operate as thin
clients or fat clients, or they can be developed so that they can host web pages

Thin Clients
 Thin clients have no custom application code and completely rely on the server for
their functionality. They do not depend as heavily on the mobile device‘s operating
system or the mobile device type as fat clients. Thin clients typically use widely
available web and Wireless Application Protocol (WAP) browsers to display the
application content pages.
Fat Clients
Fat clients typically have one to three layers of application code on them and can
operate independently from a server for some period of time. Typically, fat clients
are most useful in situations where communication between a client and server
cannot be guaranteed.
For example, a fat client application may be able to accept user input and store
data in a local database until connectivity with the server is re-established and the data
can be moved to the server.
This allows a user to continue working even if he/she is out of contact with the
server. Fat clients depend heavily on the operating system and mobile device type and
the code can be difficult to release and distribute. Fat clients can be implemented using
one, two, or three layers of application code. However, if you only use one layer it is
extremely difficult to isolate the individual areas of functionality and reuse and
distribute the code over multiple device types.
MAC PROTOCOLS
The Medium Access Control (MAC) protocol is used to provide the data link layer
of the Ethernet LAN system. The MAC protocol encapsulates a SDU (payload data)
by adding a 14 byte header (Protocol Control Information (PCI)) before the data and
appending an integrity checksum, The checksum is a 4-byte (32-bit) Cyclic
Redundancy Check (CRC) after the data. The entire frame is preceded by a small idle
period (the minimum inter-frame gap, 9.6 microsecond (µS)) and a 8 byte preamble
(including the start of frame delimiter).
Preamble
The purpose of the idle time before transmission starts is to allow a small time
interval for the receiver electronics in each of the nodes to settle after completion of
the previous frame. A node starts transmission by sending an 8 byte (64 bit) preamble
sequence. This consists of 62 alternating 1's and 0's followed by the pattern 11. Strictly
speaking the last byte which finished with the '11' is known as the "Start of Frame
Delimiter". When encoded using Manchester encoding, at 10 Mbps, the 62 alternating
bits produce a 10 MHz square wave (one complete cycle each bit period).
 The purpose of the preamble is to allow time for the receiver in each node to achieve
lock of the receiver Digital Phase Lock Loop which is used to synchronise the receive
data clock to the transmit data clock. At the point when the first bit of the preamble is
received, each receiver may be in an arbitrary state (i.e. have an arbitrary phase for its
local clock). During the course of the preamble it learns the correct phase, but in so
doing it may miss (or gain) a number of bits. A special pattern is therefore used to
mark the last two bits of the preamble. When this is received, the Ethernet receive
interface starts collecting the bits into bytes for processing by the MAC layer. It also
confirms the polarity of the transition representing a '1' bit to the receiver (as a check
in case this has been inverted).

Header

data The header consists of three parts:

A 6-byte destination address, which specifies either a single recipient node
(unicast mode), a group of recipient nodes (multicast mode), or the set of all recipient
nodes (broadcast mode).
A 6-byte source address, which is set to the sender's globally unique node
address. This may be used by the network layer protocol to identify the sender, but
usually other mechanisms are used (e.g.arp). Its main function is to allow address
learning which may be used to configure the filter tables in a bridge.
A 2-byte type field, which provides a Service Access Point (SAP) to identify the
type of protocol being carried (e.g. the values 0x0800 is used to identify the
IP network protocol, other values are used to indicate other network layer
protocols).
CRC
The final field in an Ethernet MAC frame is called a Cyclic Redundancy Check
(sometimes also known as a Frame Check Sequence). A 32-bit CRC provides error
detection in the case where line errors (or transmission collisions in Ethernet) result
in corruption of the MAC frame. Any frame with an invalid CRC is discarded by the
MAC receiver without further processing. The MAC protocol does not provide any
indication that a frame has been discarded due to an invalid CRC.
The link layer CRC therefore protects the frame from corruption while being
transmitted over the physical medium (cable). A new CRC is added if the packet is
forwarded by the router on another Ethernet link. While the packet is being processed
by the router the packet data is not protected by the CRC. Router processing errors
must be detected by network or transport-layer checksums.
Inter Frame Gap
After transmission of each frame, a transmitter must wait for a period of 9.6
microseconds (at 10 Mbps) to allow the signal to propagate through the receiver
electronics at the destination. This period of time is known as the Inter-Frame Gap
(IFG). While every transmitter must wait for this time between sending frames,
receivers do not necessarily see a "silent" period of 9.6 microseconds. The way in
which repeaters operate is such that they may reduce the IFG between the frames
which they regenerate
Byte Order
It is important to realise that nearly all serial communications systems transmit the
least significant bit of each byte first at the physical layer. Ethernet supports broadcast,
unicast, and multicast addresses. The appearance of a multicast address on the cable
(in this case an IP multicast
address, with group set to the bit pattern 0xxx xxxx xxxx xxxx xxxx xxxx) is therefore
as shown below (bits transmitted from left to right):
1 = Assigned for other uses
However, when the same frame is stored in the memory of a computer, the
bits are

ordered such that the least significant bit of each byte is stored in the right most
position (the bits are transmitted right-to-left within bytes, bytes transmitted left-to-
right):

WIRELESS MAC ISSUES

The three important issues are:
1. Half Duplex operation –> either send or receive but not both at a given
time
2. Time varying channel
3. Burst channel errors
1. Half Duplex Operation
In wireless, it‘s difficult to receive data when the transmitter is sending the data,
because: When node is transmitting, a large fraction of the signal energy leaks into the
receiver path. The transmitted and received power levels can differ by orders of
magnitude. The leakage signal typically has much higher power than the received
signal -―Impossible to detect a received signal, while transmitting data‖. Collision
detection is not possible, while sending data. As collision cannot be detected by the
sender, all proposed protocols attempt to minimize the probability of collision - Focus
on collision avoidance.
2. Time Varying Channel
Three mechanisms for radio signal propagation

1. Reflection – occurs when a propagating wave impinges upon an object that has
very large dimensions than the wavelength of the radio wave e.g. reflection
occurs from the surface of the earth and from buildings and walls.
 2. Diffraction – occurs when the radio path between the transmitter and the
receiver is obstructed by a surface with sharp edges.

3. Scattering – occurs when the medium through which the wave travels consists
of objects with.
The received signal by a node is a superposition of time-shifted and attenuated
versions of the transmitted signals the received signal varies with time .The time
varying signals (time varying channel) phenomenon also known as multipath
propagation. The rate of variation of channel is determined by the coherence time
of the channel Coherence time is defined as time within which When a node‘s
received signal strength drops below a certain threshold the node is said to be in
fade .Handshaking is widely used strategy to ensure the link quality is good enough
for data communication. A successful handshake between a sender and a receiver
(small message) indicates a good communication link.
3. Burst Channel Errors
As a consequence of time varying channel and varying signals strengths errors are
introduced in the transmission (Very likely) for wire line networks the bit error rate
(BER) is the probability of packet error is small .For wire line networks the errors are
due to random For wireless networks the BER is as high. For wireless networks the
errors are due to node being in fade as a result errors occur in a long burst. Packet loss
due to burst errors - mitigation techniques
1. Smaller packets.
2. Forward Error Correcting Codes.
3. Retransmissions (Acks)
Location Dependent Carrier Sensing
Location Dependent Carrier Sensing results in three types of nodes that protocols
need to deal with
Hidden Nodes: Even if the medium is free near the transmitter, it may not be free near
the intended receiver

Exposed Nodes: Even if the medium is busy near the transmitter, it may be free
near the intended receiver.
Capture: Capture occurs when a receiver can cleanly receive a transmission from
one of two simultaneous transmissions
Hidden Node/Terminal Problem
A hidden node is one that is within the range of the intended destination but out of
range of sender Node B can communicate with A and C both A and C cannot hear
each other When A transmits to B, C cannot detect the transmission using the carrier
sense mechanism C falsely thinks that the channel is idle
Exposed Nodes
An exposed node is one that is within the range of the sender but out of range of
destination .when a node‘s received signal strength drops below a certain threshold the
node is said to be in fade .Handshaking is widely used strategy to ensure the link
quality is good enough for data communication. A successful handshake between a
sender and a receiver (small message) indicates a good communication link.
In theory C can therefore have a parallel transmission with any node that cannot
hear the transmission from B, i.e. out of range of B. But C will not transmit to any
node because its an exposed node. Exposed nodes waste bandwidth.
Capture
Capture is said to occur when a receiver can cleanly receive a transmission from
one of two simultaneous transmissions both within its range Assume node A and D
transmit simultaneously to B. The signal strength received from D is much higher than
that from A, andD‘s transmission can be decoded without errors in presence of
transmissions from A.D has captured A. Capture is unfair because it gives preference
to nodes that are closer to the receiver. It may improve protocol performance.

FIXED ASSIGNMENT SCHEMES

TDMA
Time Division Multiple Access (TDMA) is a digital wireless telephony
transmission technique. TDMA allocates each user a different time slot on a given
frequency. TDMA divides each cellular channel into three time slots in order to
increase the amount of data that can be carried.
TDMA technology was more popular in Europe, Japan and Asian countries,
where as CDMA is widely used in North and South America. But now a days both
technologies are very popular through out of the world.
Advantages of TDMA:

 TDMA can easily adapt to transmission of data as well as

voice communication.

 TDMA has an ability to carry 64 kbps to 120 Mbps of data rates.

******************
 UNIT - II

OVERVIEW OF MOBILE IP
Mobile IP is an open standard, defined by the Internet Engineering Task Force
(IETF) RFC 3220. By using Mobile IP, you can keep the same IP address, stay
connected, and maintain ongoing applications while roaming between IP networks.
Mobile IP is scalable for the Internet because it is based on IP—any media that can
support IP can support Mobile IP.
The Cisco Mobile Networks feature enables a mobile access router and its subnets
to be mobile and maintain all IP connectivity, transparent to the IP hosts connecting
through this mobile access router.
Currently, this feature is a static network implementation that supports
stub routers only. In IP networks, routing is based on stationary IP addresses. A
device on a network is reachable through normal IP routing by the IP address it is
assigned on the network. When a device roams away from its home network, it is no
longer reachable by using normal IP routing. This results in the active sessions of the
device being terminated.
Mobile IP enables users to keep the same IP address while travelling to a
different network, ensuring that a roaming individual can continue communication
without sessions or connections being dropped. Because the mobility functions of
Mobile IP are performed at the network layer rather than the physical layer, the
mobile device can span different types of wireless and wire line networks while
maintaining connections. Remote login, remote printing, and file transfers are
examples of applications where it is desirable not to interrupt communications while
an individual roams across network boundaries.
Also, certain network services, such as software licenses and access privileges,
are based on IP addresses. Changing these IP addresses could compromise the
network services. A device that can roam while appearing to a user to be at its home
network is called a mobile node. Examples of mobile nodes include: a personal digital
assistant, a laptop computer, or a data-ready cellular phone—that can change its
point of attachment from one network or subnet to another.
This mobile node can travel from link to link and maintain communications
using the same IP address. There is no need for any changes to applications, because
the solution is at the network layer, which provides the transparent network
mobility. The Cisco Mobile Networks feature comprises three components—the
mobile access router (MR), home agent (HA), and foreign agent (FA). Figure shows
the three components (mobile access router, home agent, and foreign agent) and
their relationships within the mobile network.

The mobile access router functions similarly to the mobile node with one key
difference—the mobile access router allows entire networks to roam. For example,
an airplane with a mobile access router can fly around the world while passengers
stay connected to the Internet. This communication is accomplished by Mobile IP
aware routers tunnelling packets, which are destined to hosts on the mobile
networks, to the location where the mobile access router is visiting.
The mobile access router then forwards the packets to the destination device.
These devices can be mobile nodes without Mobile IP client software. The mobile
access router eliminates the need for a Mobile IP client. The mobile access router
―hides‖ the IP roaming from the local IP nodes so that the local nodes appear to be
directly attached to the home network. A home agent is a router on the home
network of the mobile access router. It provides the anchoring point for the mobile
networks.
The home agent maintains an association between the home IP address of the
mobile access router and its care-of address, which is the current location of the
mobile access router on a foreign or visited network. The home agent is responsible
for keeping track of where the mobile access router roams and tunnelling packets to
the current location of the mobile network. The home agent also inserts the mobile
networks into its routing table.
 A foreign agent is a router on a foreign network that assists the mobile access
router in informing its home agent of its current care-of address. It functions as the
point of attachment to the mobile access router, delivering packets from the home
agent to the mobile access router. The foreign agent is a fixed router with a direct
logical connection to the mobile access router. The mobile access router and foreign
agent need not be connected directly by a wireless link. For example, if the mobile
access router is roaming, the connection between the foreign agent and mobile
access router occurs on interfaces that are not on the same subnet. This feature does
not add any new functionality to the foreign agent component.

FEATURES OF MOBILE IP
Mobile Internet Protocol (Mobile IP) was created in order to provide better
mobile connectivity without interrupting computers that are already connected to a
network. When mobile devices were introduced, there was no network technology in
place for these devices to connect to the Internet. Mobile IP created a new subset of IP
connectivity that worked within the already established system, keeping network
engineers from having to scrap and reinvent the way Internet connection works.

Roaming Connectivity
 Mobile IP allows mobile devices to connect to the Internet when they are not at
their home network. This lets laptops connect to hotspots and it lets phones connect
through 3G and other Internet network sources. An IP address lets a network know
where to send and receive information from on a network. Mobile IP uses an address
that references its home network while finding a location on the new network. This
keeps Mobile IP from knocking other computers off of a network, because each
computer comes from a unique network and has a unique number.
Compatibility
Mobile IP is compatible with most networks that offer the Internet. This include
the 3G network used for mobile televisions; Internet hotspots found in cafes, airports
and book stores; and all home network devices. Early attempts at Mobile IP would
only work with certain routers or certain types of networks. Mobile IP today has no
special requirements because the system is universal and fits within the original IP
infrastructure.
Tunnelling and Reverse Tunnelling
The method by which mobile IP receives information from a network is called
tunnelling. A network cannot directly send information to a mobile IP device. In order
to get this information the mobile device must create an IP address within its new IP
address. This allows the network to send information to the IP address through the
―tunnel‖ of the two new IPs. Firewalls and routers can sometimes block tunnelling by
enabling what is called ingress filtering. Mobile IP also can use the process of reverse
tunnelling, which is a similar process that reverses the flow of information to achieve
the same result as tunnelling.
Cordless
The greatest feature of Mobile IP is that there are no cords needed to complete
the network connection. The standard IP required that networks be connected by a
phone line or Ethernet cord. With Mobile IP, the device finds the network
automatically and attempts to establish a connection. Some mobile capable devices
like laptop computers have the ability to connect using the Mobile IP or using the
standard IP with an Ethernet or phone cord.

FEATURES OF MOBILE IP
Mobile Internet Protocol (Mobile IP) was created in order to provide better
mobile connectivity without interrupting computers that are already connected to a
network. When mobile devices were introduced, there was no network technology in
place for these devices to connect to the Internet. Mobile IP created a new subset of
IP connectivity that worked within the already established system, keeping network
engineers from having to scrap and reinvent the way Internet connection works.
Roaming Connectivity
 Mobile IP allows mobile devices to connect to the Internet when they are not
at their home network. This lets laptops connect to hotspots and it lets phones
connect through 3G and other Internet network sources. An IP address lets a network
know where to send and receive information from on a network. Mobile IP uses an
address that references its home network while finding a location on the new
network. This keeps Mobile IP from knocking other computers off of a network,
because each computer comes from a unique network and has a unique number.
Compatibility
Mobile IP is compatible with most networks that offer the Internet. This include
the 3G network used for mobile televisions; Internet hotspots found in cafes, airports
and book stores; and all home network devices. Early attempts at Mobile IP would
only work with certain routers or certain types of networks. Mobile IP today has no
special requirements because the system is universal and fits within the original IP
infrastructure.
Tunnelling and Reverse Tunnelling
The method by which mobile IP receives information from a network is called
tunnelling. A network cannot directly send information to a mobile IP device. In order
to get this information the mobile device must create an IP address within its new IP
address. This allows the network to send information to the IP address through the
―tunnel‖ of the two new IPs. Firewalls and routers can sometimes block tunnelling
by enabling what is called ingress filtering. Mobile IP also can use the process of
reverse tunnelling, which is a similar process that reverses the flow of information to
achieve the same result as tunnelling.
Cordless
The greatest feature of Mobile IP is that there are no cords needed to complete
the network connection. The standard IP required that networks be connected by a
phone line or Ethernet cord. With Mobile IP, the device finds the network
automatically and attempts to establish a connection. Some mobile capable devices
like laptop computers have the ability to connect using the Mobile IP or using the
standard IP with an Ethernet or phone cord.

KEY MECHANISM IN MOBILE IP

The Mobile IP process has three main phases, which are discussed in the
following sections.
 I. Agent Discovery - A Mobile Node discovers its Foreign and Home
Agents during agent discovery.

II. Registration - The Mobile Node registers its current location with the
Foreign Agent and Home Agent during registration.

III. Tunnelling - A reciprocal tunnel is set up by the Home Agent to the care-
of address (current location of the Mobile Node on the foreign network) to
route packets to the Mobile Node as it roams.
i. Agent Discovery
During the agent discovery phase, the Home Agent and Foreign Agent
advertise their services on the network by using the ICMP Router Discovery Protocol
(IRDP). The Mobile Node listens to these advertisements to determine if it is
connected to its home network or foreign network.
The IRDP advertisements carry Mobile IP extensions that specify whether an
agent is a Home Agent, Foreign Agent, or both; its care-of address; the types of
services it will provide such as reverse tunnelling and generic routing encapsulation
(GRE); and the allowed registration lifetime or roaming period for visiting Mobile
Nodes. Rather than waiting for agent advertisements, a Mobile Node can send out an
agent solicitation. This solicitation forces any agents on the link to immediately send
an agent advertisement.
If a Mobile Node determines that it is connected to a foreign network, it
acquires a care-of address. Two types of care-of addresses exist:

 Care-of address acquired from a Foreign Agent

 Co-located care-of address

A Foreign Agent care-of address is an IP address of a Foreign Agent that has an
interface on the foreign network being visited by a Mobile Node. A Mobile Node that
acquires this type of care-of address can share the address with other Mobile Nodes.
A co-located care-of address is an IP address temporarily assigned to the interface of
the Mobile Node itself.

A co-located care-of address represents the current position of the Mobile

Node on the foreign network and can be used by only one Mobile Node at a time.
When the Mobile Node hears a Foreign Agent advertisement and detects that it has
moved outside of its home network, it begins registration.
ii.Registration
 The Mobile Node is configured with the IP address and mobility security
association (which includes the shared key) of its Home Agent. In addition, the
Mobile Node is configured with either its home IP address, or another user identifier,
such as a Network Access Identifier.
The Mobile Node uses this information along with the information that it learns
from the Foreign Agent advertisements to form a Mobile IP registration request. It
adds the registration request to its pending list and sends the registration request to
its Home Agent either through the Foreign Agent or directly if it is using a co-located
care-of address and is not required to register through the Foreign Agent.
If the registration request is sent through the Foreign Agent, the Foreign Agent
checks the validity of the registration request, which includes checking that the
requested lifetime does not exceed its limitations, the requested tunnel
encapsulation is available, and that reverse tunnel is supported. If the registration
request is valid, the Foreign Agent adds the visiting Mobile Node to its pending list
before relaying the request to the Home Agent. If the registration request is not valid,
the Foreign Agent sends a registration reply with appropriate error code to the
Mobile Node.
The Home Agent checks the validity of the registration request, which includes
authentication of the Mobile Node. If the registration request is valid, the Home
Agent creates a mobility binding (an association of the Mobile Node with its care-of
address), a tunnel to the care-of address, and a routing entry for forwarding packets
to the home address through the tunnel.
The Home Agent then sends a registration reply to the Mobile Node through the
Foreign Agent (if the registration request was received via the Foreign Agent) or
directly to the Mobile Node. If the registration request is not valid, the Home Agent
rejects the request by sending a registration reply with an appropriate error code.
The Foreign Agent checks the validity of the registration reply, including ensuring
that an associated registration request exists in its pending list. If the registration
reply is valid, the Foreign Agent adds the Mobile Node to its visitor list, establishes a
tunnel to the Home Agent, and creates a routing entry for forwarding packets to the
home address. It then relays the registration reply to the Mobile Node.

Finally, the Mobile Node checks the validity of the registration reply, which
includes ensuring an associated request is in its pending list as well as proper
authentication of the Home Agent. If the registration reply is not valid, the Mobile
Node discards the reply. If a valid registration reply specifies that the registration is
accepted, the Mobile Node is confirmed that the mobility agents are aware of its
roaming. In the co-located care-of address case, it adds a tunnel to the Home Agent.
Subsequently, it sends all packets to the Foreign Agent.

The Mobile Node reregisters before its registration lifetime expires. The Home
Agent and Foreign Agent update their mobility binding and visitor entry, respectively,
during re-registration. In the case where the registration is denied, the Mobile Node
makes the necessary adjustments and attempts to register again. For example, if the
registration is denied because of time mismatch and the Home Agent sends back its
time stamp for synchronization, the Mobile Node adjusts the time stamp in future
registration requests.

Thus, a successful Mobile IP registration sets up the routing mechanism for

transporting packets to and from the Mobile Node as it roams.

iii.Tunnelling

The Mobile Node sends packets using its home IP address, effectively maintaining the
appearance that it is always on its home network. Even while the Mobile Node is
roaming on foreign networks, its movements are transparent to correspondent
nodes.Data packets addressed to the Mobile Node are routed to its home network,
where the Home Agent now intercepts and tunnels them to the care-of address
toward the Mobile Node. Tunnelling has two primary functions: encapsulation of the
data packet to reach the tunnel endpoint, and decapsulation when the packet is
delivered at that endpoint. The default tunnel mode is IP Encapsulation within IP
Encapsulation. Optionally, GRE and minimal encapsulation within IP may be
used.Typically, the Mobile Node sends packets to the Foreign Agent, which routes
them to their final destination, the Correspondent Node, as shown in Figure 2.

Packet Forwarding
However, this data path is topologically incorrect because it does not reflect the true
IP network source for the data — rather, it reflects the home network of the Mobile
Node. Because the packets show the home network as their source inside a foreign
network, an access control list on routers in the network called ingress filtering drops
the packets instead of forwarding them. A feature called reverse tunnelling solves
this problem by having the Foreign Agent tunnel packets back to the Home Agent
when it receives them from the Mobile Node.

Reverse Tunnel
 Tunnel MTU discovery is a mechanism for a tunnel encapsulator such as the
Home Agent to participate in path MTU discovery to avoid any packet fragmentation
in the routing path between a Correspondent Node and Mobile Node. For packets
destined to the Mobile Node, the Home Agent maintains the MTU of the tunnel to
the care-of address and informs the Correspondent Node of the reduced packet size.
This improves routing efficiency by avoiding fragmentation and reassembly at the
tunnel endpoints to ensure that packets reach the Mobile Node.

Security
Mobile IP uses a strong authentication scheme for security purposes. All
registration messages between a Mobile Node and Home Agent are required to
contain the Mobile-Home Authentication Extension (MHAE).

The integrity of the registration messages is protected by a preshared 128-bit

key between a Mobile Node and Home Agent. The keyed message digest algorithm 5
(MD5) in "prefix+suffix" mode is used to compute the authenticator value in the
appended MHAE, which is mandatory. Mobile IP also supports the hash-based
message authentication code (HMAC-MD5). The receiver compares the authenticator
value it computes over the message with the value in the extension to verify the
authenticity.

Optionally, the Mobile-Foreign Authentication Extension and Foreign-Home

Authentication Extension are appended to protect message exchanges between a
Mobile Node and Foreign Agent and between a Foreign Agent and Home Agent,
respectively.

Replay protection uses the identification field in the registration messages as a

timestamp and sequence number. The Home Agent returns its time stamp to
synchronize the Mobile Node for registration.

Cisco IOS software allows the mobility keys to be stored on an authentication,

authorization, and accounting (AAA) server that can be accessed using TACACS+ or
RADIUS protocols. Mobile IP in Cisco IOS software also contains registration filters,
enabling companies to restrict who is allowed to register.

ROUTE OPTIMIZATION
Mobile IPv4 route optimization

Mobile IPv4 route optimization is a proposed extension to the Mobile IPv4

protocol. It provides enhancements to the routing of data grams between the
mobile node and to the correspondent node. The enhancements provide means for a
correspondent node to tunnel data grams directly to the mobile node or to its foreign
agent care-of address.

Route optimization messages and data structures

The route optimization extension adds a conceptual data structure, the binding
cache, to the correspondent node and to the foreign agent. The binding cache
contains bindings for mobile nodes' home addresses and their current care-of
addresses. With the binding the correspondent node can tunnel data grams directly
to the mobile node's care-of address.

Every time the home agent receives a datagram that is destined to a mobile
node currently away from home, it sends a binding update to the correspondent
node to update the information in the correspondent node's binding cache. After this
the correspondent node can directly tunnel packets to the mobile node. Thus direct
bi-directional communication is achieved with route optimization.

Direct routing with route optimization and foreign agent care-of address.
Route optimization adds four new UDP-messages to the Mobile IPv4 protocol:

Binding update informs the correspondent node or foreign agent of the mobile
node's new location. It is sent by the home agent or in the case of previous foreign
agent notification, by the new foreign agent, as shown in Figure 4. The binding
update contains the care-of address and the home address of the mobile node and
also the lifetime of the binding. It also must contain a mobile IP authentication
extension. An identification number may also be present to provide a way of
matching updates with acknowledgements and to protect against replay attacks.

Binding acknowledgement is sent by the correspondent node or the foreign

agent in response to the binding update. It contains the mobile node's home address
and a status code. It also contains an identification number, if there was one in the
corresponding binding update.

Binding request is sent by the correspondent node to the home agent to

request a binding update. It contains the home address of the queried mobile node
and possibly an identification number.

Binding warning is sent by the previous foreign agent in response to receiving a

tunnelled datagram for a mobile node for which it has a binding and for which it is
not acting as the current foreign agent. The binding warning is sent to the home
agent. It contains the home address of the mobile node and the address of the
correspondent node that does not have up to date information of the mobile node's
current care-of address. With this information the home agent can send a binding
update to the correspondent node.

Binding update to correspondent node

The effect on static routes

As the correspondent node learns the care-of address of the mobile node from the
binding update, it can tunnel data grams directly to the mobile node's care-of
address . Thus only the first data grams are routed via the home agent. This reduces
the network load and also reduces the delays caused by routing. Thus the
optimization is valuable to mobile nodes that visit networks located far from their
home agent.

However, the overhead caused by tunnelling is not decreased. The

correspondent node's use of minimal encapsulation is a partial remedy, if both the
encapsulator and the decapsulator support it. Ingress filtering may also prevent the
mobile node from sending data grams directly to the correspondent node. The use of
direct reverse tunnelling from the care-of address to the correspondent node's
address is a possible solution to ingress filtering. However, it is not possible with
foreign agent care-of addresses, since the current reverse tunnelling standard
requires the foreign agent to tunnel all packets to the home agent of the mobile
node.
Smooth handoffs with route optimization

In the static case the protocol is fairly simple, but handoffs somewhat
complicate the situation. When the correspondent node has an out of date entry for
the mobile node's care-of address it tries to send the tunnelled datagram to the
mobile node's previous location and the datagram is lost. To solve this problem the
protocol includes the previous foreign agent notification mechanism, which adds a
binding cache to the foreign agent.

When a mobile node moves to a new sub network it sends a registration

request to the new foreign agent. The registration request may contain a previous
foreign agent notification extension. Upon receiving such a request the foreign agent
builds a binding update and sends it to the previous foreign agent. The previous
foreign agent can then, after authenticating the update, create a binding for the
mobile node. With this binding it can re-tunnel data grams to the mobile node's new
care-of address. The re-tunnelling requires foreign agent care-of addresses in order
for the agents to act as tunnel endpoints.

The previous foreign agent notification mechanism provides temporary

localization of the handoffs. It does not reduce the signalling load between the home
agent and the mobile node, but reduces the number of data grams lost due to
correspondent nodes with out-of date bindings.

Security considerations

Since the correspondent nodes and foreign agents have binding caches, which
change the routing of data grams destined to mobile nodes, the binding updates
must be authenticated. The authentication is performed in a similar manner as in
base Mobile IPv4. All binding updates contain a route optimization or smooth handoff
authentication extension. This extension contains a hash, which is calculated from
the datagram and the shared secret.
The correspondent node and the mobile node's home agent need a security
association. This association is used for the authentication of the binding updates.
Since the mobile node sends a binding update directly to its previous foreign
 agent, they also need a security association. If the security associations are not
preconfigured they can be established via a key management protocol such as
ISAKMP or SKIP.

General deployment requirements

In order to make use of the binding updates the correspondent nodes must
be able to process and authenticate them and be able to encapsulate data grams.
To establish this, the network stacks of the operating systems require changes.
Since correspondent nodes need to establish a security association with the home
agent and foreign agents need to establish one with the mobile node, a widely
deployed key management system is obviously needed. Otherwise only nodes
with statically configured security associations can benefit from the binding
updates.

Mobile IPv6 and route optimization

Main characteristics of Mobile IPv6

Whereas Mobile IP was added on top of the IPv4 protocol, in IPv6 mobility support is
built into the IP-layer. In mobile IPv6 route optimization is an essential part of the
protocol. Mobile nodes have a binding update list, which contains the bindings other
nodes have for it. Correspondent nodes and home agents have a binding cache,
which contains the home and care-of addresses of mobile nodes they have been
recently communicating with. All signalling is performed via destination options
that are appended to the base IPv6 header. Thus all signalling traffic can be
piggybacked on data grams with a data payload, as in Figure 5.

The destination options are:

 Binding update option, which is sent by the mobile node to its home agent and
correspondent nodes to inform them of a change of location.

 Binding acknowledgement option, which is sent in response to the binding
update.

 Binding request option, with which a node can request a new binding
update from the mobile node, when the binding is about to expire.
• Home address option, which the mobile node appends to all data grams it sends
while away from its home network. The home address option is used to avoid the
negative effects of ingress filtering by using the topologically correct care-of address
as the source address and including the home address in the option. The receiving
node will then copy the home address to the source address before passing the
packet to any transport level protocol.
All care-of addresses in Mobile IPv6 are co-located; thus foreign agents are not a part
of the protocol. Since all nodes are only required to understand the home address
option, triangle routing will occur also with mobile IPv6. However, if the
correspondent node implements the draft fully, only the first data grams it sends will
be routed via the home agent. The mobile node always sends a binding update to the
original sender of a tunnelled datagram. With this binding the correspondent node
can send data grams directly to the mobile node using a routing header.
A datagram with a routing header contains the care-of address as the
destination address and the home address in the routing extension header as the
final destination. Thus the datagram will be normally routed to the care-of
address. When the mobile node receives a datagram with a routing header it
swaps the final destination with the destination address field. The home address
option and the routing header make the mobility transparent with direct routing.

The Effect on Routing

By using direct routes in both directions the consumption of network

resources is minimized. The 40-byte IPv6 headers consume extra bandwidth when
compared to 20 byte IPv4 headers. However the use of routing header and home
address option removes the need for constant tunnelling, thus decreasing the
 bandwidth consumption. Although they both add overhead to packets they still
are considerably smaller than IPv6 headers, which would be used in tunnelling.
The destination options used for signalling can be piggybacked [4] which
decreases the signalling overhead considerably, since the options are relatively
small when compared to UDP packets.

The effect on handoffs

The IPv6 mobility support provides the previous router notification mechanism, with
which the amount of lost of packets in handoffs can be reduced. In IPv6 the mobile
node sends a binding update directly to the previous router, which consumes more
bandwidth but is faster than the mechanism used with Mobile IPv4 route
optimization.
Problems solved

Mobile IPv6 provides improvements on routing and signalling efficiency. As the

signalling can be mostly piggybacked on data packets there will be considerably less
signalling overhead between the mobile node and the correspondent nodes than in
mobile IPv4 route optimization between the home agent and the correspondent
nodes. The minimum requirements for the correspondent node provide at least
triangle routing even in the worst case, since care-of address can be used as the
source address. Hosts that are likely to communicate with mobile nodes will
probably implement the binding cache and communicate directly with the mobile
node. In both cases the routing saves network capacity and decreases delays, when
compared to reverse bi-directional tunnelling between the mobile node and
correspondent node.

The key management problem is not solved Mobile IPv6 does not solve the key
management problem, but the integration of IPSec into IPv6 is likely to result in
support for key management protocols in most operating systems implementing
IPv6.

ROUTE OPTIMIZATION

Mobile IPv4 route optimization

 Mobile IPv4 route optimization is a proposed extension to the Mobile IPv4
protocol. It provides enhancements to the routing of data grams between the
mobile node and to the correspondent node. The enhancements provide means for a
correspondent node to tunnel data grams directly to the mobile node or to its foreign
agent care-of address.

Route optimization messages and data structures

The route optimization extension adds a conceptual data structure, the binding
cache, to the correspondent node and to the foreign agent. The binding cache
contains bindings for mobile nodes' home addresses and their current care-of
addresses. With the binding the correspondent node can tunnel data grams directly
to the mobile node's care-of address.

Every time the home agent receives a datagram that is destined to a mobile
node currently away from home, it sends a binding update to the correspondent
node to update the information in the correspondent node's binding cache. After this
the correspondent node can directly tunnel packets to the mobile node. Thus direct
bi-directional communication is achieved with route optimization.

Direct routing with route optimization and foreign agent care-of address.

Route optimization adds four new UDP-messages to the Mobile IPv4 protocol:
Binding update informs the correspondent node or foreign agent of the mobile
node's new location. It is sent by the home agent or in the case of previous foreign
agent notification, by the new foreign agent, as shown in Figure 4. The binding
update contains the care-of address and the home address of the mobile node and
also the lifetime of the binding. It also must contain a mobile IP authentication
extension. An identification number may also be present to provide a way of
matching updates with acknowledgements and to protect against replay attacks.

Binding acknowledgement is sent by the correspondent node or the foreign

agent in response to the binding update. It contains the mobile node's home address
and a status code. It also contains an identification number, if there was one in the
corresponding binding update.

Binding request is sent by the correspondent node to the home agent to

request a binding update. It contains the home address of the queried mobile node
and possibly an identification number.

Binding warning is sent by the previous foreign agent in response to receiving a

tunnelled datagram for a mobile node for which it has a binding and for which it is
not acting as the current foreign agent. The binding warning is sent to the home
agent. It contains the home address of the mobile node and the address of the
correspondent node that does not have up to date information of the mobile node's
current care-of address. With this information the home agent can send a binding
update to the correspondent node.

Binding update to correspondent node

The effect on static routes

As the correspondent node learns the care-of address of the mobile node from the
binding update, it can tunnel data grams directly to the mobile node's care-of
address . Thus only the first data grams are routed via the home agent. This reduces
the network load and also reduces the delays caused by routing. Thus the
optimization is valuable to mobile nodes that visit networks located far from their
home agent.

However, the overhead caused by tunnelling is not decreased. The

correspondent node's use of minimal encapsulation is a partial remedy, if both the
encapsulator and the decapsulator support it. Ingress filtering may also prevent the
mobile node from sending data grams directly to the correspondent node. The use of
direct reverse tunnelling from the care-of address to the correspondent node's
address is a possible solution to ingress filtering. However, it is not possible with
foreign agent care-of addresses, since the current reverse tunnelling standard
requires the foreign agent to tunnel all packets to the home agent of the mobile
node.

Smooth handoffs with route optimization

 In the static case the protocol is fairly simple, but handoffs somewhat
complicate the situation. When the correspondent node has an out of date entry for
the mobile node's care-of address it tries to send the tunnelled datagram to the
mobile node's previous location and the datagram is lost. To solve this problem the
protocol includes the previous foreign agent notification mechanism, which adds a
binding cache to the foreign agent.

When a mobile node moves to a new sub network it sends a registration

request to the new foreign agent. The registration request may contain a previous
foreign agent notification extension. Upon receiving such a request the foreign agent
builds a binding update and sends it to the previous foreign agent. The previous
foreign agent can then, after authenticating the update, create a binding for the
mobile node. With this binding it can re-tunnel data grams to the mobile node's new
care-of address. The re-tunnelling requires foreign agent care-of addresses in order
for the agents to act as tunnel endpoints.

The previous foreign agent notification mechanism provides temporary

localization of the handoffs. It does not reduce the signalling load between the home
agent and the mobile node, but reduces the number of data grams lost due to
correspondent nodes with out-of date bindings.

Security considerations

Since the correspondent nodes and foreign agents have binding caches, which
change the routing of data grams destined to mobile nodes, the binding updates
must be authenticated. The authentication is performed in a similar manner as in
base Mobile IPv4. All binding updates contain a route optimization or smooth handoff
authentication extension. This extension contains a hash, which is calculated from
the datagram and the shared secret.
The correspondent node and the mobile node's home agent need a security
association. This association is used for the authentication of the binding updates.
Since the mobile node sends a binding update directly to its previous foreign
agent, they also need a security association. If the security associations are not
preconfigured they can be established via a key management protocol such as
ISAKMP or SKIP.
 General deployment requirements

In order to make use of the binding updates the correspondent nodes must
be able to process and authenticate them and be able to encapsulate data grams.
To establish this, the network stacks of the operating systems require changes.
Since correspondent nodes need to establish a security association with the home
agent and foreign agents need to establish one with the mobile node, a widely
deployed key management system is obviously needed. Otherwise only nodes
with statically configured security associations can benefit from the binding
updates.

Mobile IPv6 and route optimization

Main characteristics of Mobile IPv6

Whereas Mobile IP was added on top of the IPv4 protocol, in IPv6 mobility support is
built into the IP-layer. In mobile IPv6 route optimization is an essential part of the
protocol. Mobile nodes have a binding update list, which contains the bindings other
nodes have for it. Correspondent nodes and home agents have a binding cache,
which contains the home and care-of addresses of mobile nodes they have been
recently communicating with. All signalling is performed via destination options
that are appended to the base IPv6 header. Thus all signalling traffic can be
piggybacked on data grams with a data payload, as in Figure 5.

The destination options are:

 Binding update option, which is sent by the mobile node to its home agent and
correspondent nodes to inform them of a change of location.

 Binding acknowledgement option, which is sent in response to the binding
update.

 Binding request option, with which a node can request a new binding
update from the mobile node, when the binding is about to expire.
• Home address option, which the mobile node appends to all data grams it sends
while away from its home network. The home address option is used to avoid the
negative effects of ingress filtering by using the topologically correct care-of address
as the source address and including the home address in the option. The receiving
node will then copy the home address to the source address before passing the
packet to any transport level protocol.
All care-of addresses in Mobile IPv6 are co-located; thus foreign agents are not a part
of the protocol. Since all nodes are only required to understand the home address
option, triangle routing will occur also with mobile IPv6. However, if the
correspondent node implements the draft fully, only the first data grams it sends will
be routed via the home agent. The mobile node always sends a binding update to the
original sender of a tunnelled datagram. With this binding the correspondent node
can send data grams directly to the mobile node using a routing header.
A datagram with a routing header contains the care-of address as the
destination address and the home address in the routing extension header as the
final destination. Thus the datagram will be normally routed to the care-of
address. When the mobile node receives a datagram with a routing header it
swaps the final destination with the destination address field. The home address
option and the routing header make the mobility transparent with direct routing.

The Effect on Routing

By using direct routes in both directions the consumption of network

resources is minimized. The 40-byte IPv6 headers consume extra bandwidth when
compared to 20 byte IPv4 headers. However the use of routing header and home
address option removes the need for constant tunnelling, thus decreasing the
bandwidth consumption. Although they both add overhead to packets they still
are considerably smaller than IPv6 headers, which would be used in tunnelling.
The destination options used for signalling can be piggybacked [4] which
decreases the signalling overhead considerably, since the options are relatively
small when compared to UDP packets.
 The effect on handoffs

The IPv6 mobility support provides the previous router notification mechanism, with
which the amount of lost of packets in handoffs can be reduced. In IPv6 the mobile
node sends a binding update directly to the previous router, which consumes more
bandwidth but is faster than the mechanism used with Mobile IPv4 route
optimization.
Problems solved

Mobile IPv6 provides improvements on routing and signalling efficiency. As the

signalling can be mostly piggybacked on data packets there will be considerably less
signalling overhead between the mobile node and the correspondent nodes than in
mobile IPv4 route optimization between the home agent and the correspondent
nodes. The minimum requirements for the correspondent node provide at least
triangle routing even in the worst case, since care-of address can be used as the
source address. Hosts that are likely to communicate with mobile nodes will
probably implement the binding cache and communicate directly with the mobile
node. In both cases the routing saves network capacity and decreases delays, when
compared to reverse bi-directional tunnelling between the mobile node and
correspondent node.

The key management problem is not solved Mobile IPv6 does not solve the key
management problem, but the integration of IPSec into IPv6 is likely to result in
support for key management protocols in most operating systems implementing
IPv6.

OVERVIEW OF TCP / IP

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication

language or protocol of the Internet. It can also be used as a communications
protocol in a private network (either an intranet or an extranet). When you are set up
with direct access to the Internet, your computer is provided with a copy of the
TCP/IP program just as every other computer that you may send messages to or get
information from also has a copy of TCP/IP.
TCP/IP is a two-layer program.

The higher layer, Transmission Control Protocol, manages the assembling of a

message or file into smaller packets that are transmitted over the Internet and
received by a TCP layer that reassembles the packets into the original message. The
lower layer, Internet Protocol, handles the address part of each packet so that it gets
to the right destination. Each gateway computer on the network checks this address
to see where to forward the message. Even though some packets from the same
message are routed differently than others, they'll be reassembled at the destination.

TCP/IP uses the client/server model of communication in which a computer user (a

client) requests and is provided a service (such as sending a Web page) by another
computer (a server) in the network. TCP/IP communication is primarily point-to-
point, meaning each communication is from one point (or host computer) in the
network to another point or host computer.

TCP/IP and the higher-level applications that use it are collectively said to be
"stateless" because each client request is considered a new request unrelated to any
previous one (unlike ordinary phone conversations that require a dedicated
connection for the call duration). Being stateless frees network paths so that
everyone can use them continuously. (Note that the TCP layer itself is not stateless as
far as any one message is concerned. Its connection remains in place until all packets
in a message have been received.)

Many Internet users are familiar with the even higher layer application protocols that
use TCP/IP to get to the Internet. These include the World Wide Web's Hypertext
Transfer Protocol (HTTP), the File Transfer Protocol (FTP), Telnet (Telnet) which lets
you logon to remote computers, and the Simple Mail Transfer Protocol (SMTP). These
and other protocols are often packaged together with TCP/IP as a "suite."

Personal computer users with an analog phone modem connection to the Internet
usually get to the Internet through the Serial Line Internet Protocol (SLIP) or the
Point-to- Point Protocol (PPP). These protocols encapsulate the IP packets so that
they can be sent over the dial-up phone connection to an access provider's modem.
Protocols related to TCP/IP include the User Datagram Protocol (UDP), which is used
instead of TCP for special purposes. Other protocols are used by network host
computers for exchanging router information. These include the Internet Control
Message Protocol (ICMP), the Interior Gateway Protocol (IGP), the Exterior Gateway
Protocol (EGP), and the Border Gateway Protocol (BGP).

TCP/IP Protocols for the Web

Web browsers and servers use TCP/IP protocols to connect to the Internet.
Common TCP/IP protocols are:

i.HTTP - Hyper Text Transfer Protocol

HTTP takes care of the communication between a web server and a web
browser. HTTP is used for sending requests from a web client (a browser) to a web
server, returning web content (web pages) from the server back to the client.

ii.HTTPS - Secure HTTP

HTTPS takes care of secure communication between a web server and a web
browser. HTTPS typically handles credit card transactions and other sensitive data.

iii.FTP - File Transfer Protocol

FTP takes care of transmission of files between computers.

TCP/IP Protocols for Email

E-mail programs use TCP/IP for sending and receiving e-mails. The TCP/IP protocols
for email are:
i.SMTP - Simple Mail Transfer Protocol

SMTP takes care of sending emails. Often emails are sent to an email server
(SMTP server), then to other servers, and finally to its destination. SMTP can only
transmit pure text. It cannot transmit binary data like pictures, sounds or movies.

ii.MIME - Multi-purpose Internet Mail Extensions

The MIME protocol lets SMTP transmit multimedia files including voice, audio,
and binary data across TCP/IP networks. The MIME protocol converts binary data to
pure text, before it is sent.

iii.POP - Post Office Protocol

The POP protocol is used by email programs to retrieve emails from an email
server. If your email program uses POP, all your emails are downloaded to your email
program (also called email client), each time it connects to your email server.
iv.IMAP - Internet Message Access Protocol

The IMAP protocol works much like the POP protocol. The main difference is
that the IMAP protocol will not automatically download all your emails each time
your email program connects to your email server.

The IMAP protocol allows you to look through your email messages at the
email server before you download them. With IMAP you can choose to download
your messages or just delete them. This way IMAP is perfect if you need to connect
to your email server from different locations, but only want to download your
messages when you are back in your office.

Other TCP/IP Protocols

ARP - Address Resolution Protocol

ARP is used by IP to find the hardware address of a computer network card

based on the IP address.

BOOTP - Boot Protocol

BOOTP is used for booting (starting) computers from the network.

DHCP - Dynamic Host Configuration Protocol

DHCP is used for allocation of dynamic IP addresses to computers in a network.

ICMP - Internet Control Message Protocol

ICMP takes care of error-handling in the network.

LDAP - Lightweight Directory Access Protocol

LDAP is used for collecting information about users and e-mail addresses from
the internet.

NTP - Network Time Protocol

NTP is used to synchronize the time (the clock) between computers.

PPTP - Point to Point Tunnelling Protocol

PPTP is used for setting up a connection (tunnel) between private networks.

RARP - Reverse Address Resolution Protocol

RARP is used by IP to find the IP address based on the hardware address of

a computer network card.

SNMP - Simple Network Management Protocol

SNMP is used for administration of computer networks.

SSL - Secure Sockets Layer

The SSL protocol is used to encrypt data for secure data transmission.

TLS - Transport Layer Security

The TLS protocol is a newer and more secure version of SSL.

ARCHITECTURE OF TCP / IP
 When communication among computers from different vendors is desired,
the software development effort can be a nightmare. Different vendors use
different data formats and data exchange protocols. Even within one vendor's
product line, different model computers may communicate in unique ways.

As the use of computer communications and computer networking

proliferates, a one-at-a-time, special-purpose approach to communications
software development is too costly to be acceptable. The only alternative is for
computer vendors to adopt and implement a common set of conventions. For this
to happen, standards are needed. Such standards would have two benefits:

i. Vendors feel encouraged to implement the standards because of an expectation

that, because of wide usage of the standards, their products would be less
marketable without them.

ii. Customers are in a position to require that the standards be implemented by any
vendor wishing to propose equipment to them.
 However, no single standard will suffice. Any distributed application, such
as electronic mail or client/server interaction, requires a complex set of
communications
functions for proper operation. Many of these functions, such as reliability
mechanisms, are common across many or even all applications. Thus, the
communications task is best viewed as consisting of a modular architecture, in
which the various elements of the architecture perform the various required
functions. Hence, before standards can be developed, there should be a structure,
or protocol architecture, that defines the communications tasks.

Two protocol architectures have served as the basis for the development
of interoperable communications standards: the TCP/IP protocol suite and the
Open Systems Interconnection (OSI) reference model. TCP/IP is the most widely
used interoperable architecture, and has won the "protocol wars." Although some
useful standards have been developed in the context of OSI, TCP/IP is now the
universal interoperable protocol architecture. No product should be considered as
part of a business information system that does not support TCP/IP.

TCP/IP is a result of protocol research and development conducted on the

experimental packet-switched network, ARPANET, funded by the Defence
Advanced Research Projects Agency (DARPA), and is generally referred to as
the TCP/IP protocol suite. This protocol suite consists of a large collection of
protocols that have been issued as Internet standards by the Internet Activities
Board (IAB).

TCP/IP Layers

There is no official TCP/IP protocol model, as there is in the case of OSI.

However, based on the protocol standards that have been developed, we can
organize the communication task for TCP/IP into five relatively independent
layers:

 Application layer

 Host-to-host, or transport layer

 Internet layer

 Network access layer

 Physical layer

The physical layer covers the physical interface between a data

transmission device (such as a workstation or computer) and a transmission
medium or network. This layer is concerned with specifying the characteristics of
the transmission medium, the nature of the signals, the data rate, and related
matters.

The network access layer is concerned with the exchange of data between an end
system and the network to which it's attached. The sending computer must provide
the network with the address of the destination computer, so that the network can
route the data to the appropriate destination. The sending computer may need to
invoke certain services, such as priority, that might be provided by the network.

The specific software used at this layer depends on the type of network to be
used; different standards have been developed for circuit-switching, packet-switching
(for example, frame relay), local area networks (such as Ethernet), and others. Thus,
it makes sense to separate those functions having to do with network access into a
separate layer. By doing this, the remainder of the communications software, above
the network access layer, need not be concerned about the specifics of the network
to be used. The same higher-layer software should function properly regardless of
the particular network to which the computer is attached.
The network access layer is concerned with access to and routing data across a
network for two end systems attached to the same network. In those cases where
two devices are attached to different networks, procedures are needed to allow data
to traverse multiple interconnected networks. This is the function of the Internet
layer. The Internet protocol (IP) is used at this layer to provide the routing function
across multiple networks. This protocol is implement not only in the end systems but
also in routers. A router is a processor that connects two networks; its primary
function is to relay data from one network to the other on its route from the source
to the destination end system.

Regardless of the nature of the applications that are exchanging data, there is
usually a requirement that data be exchanged reliably. That is, we want to be assured
that all of the data arrives at the destination application, in the order in which it was
sent. The mechanisms for providing reliability are essentially independent of the
nature of the applications. Thus, it makes sense to collect those mechanisms in a
common layer shared by all applications; this is referred to as the host-to-host or
transport layer. The transmission control protocol (TCP) is the most commonly used
protocol to provide this functionality.

Finally, the application layer contains the logic needed to support the various user
applications. For each type of application, such as file transfer, a separate module is
needed that's peculiar to that application.

The Application Layer

The application layer defines how certain services operate and how they can be used.
Examples are the FTP service for transferring files, HTTP for serving Web pages and
SMTP for e-mail.
These services are defined in a rather abstract manner. Two parties, called the client
and the server, set up a connection over which they exchange messages in
accordance with a specific protocol. The client starts the protocol by requesting the
service. Often the next step is for the server to authenticate the client, for example
by asking for a password or by executing a public-key based protocol.

Taking e-mail as an example, the protocol in question is called the

Simple Mail Transfer Protocol (SMTP). The client and the server set up an SMTP
connection over which they exchange identifying information. The client then tells
who the message is from and who the intended recipient is. The server then indicates
whether it accepts or refuses the message (for example if it's spam or the intended
recipient is unknown). If the message is accepted, the client sends the actual content
of the message and the server stores it in the right mailbox.
The Transport Layer
On the Internet, the transport layer is realized by two protocols. The first is the
Transmission Control Protocol (TCP) and the second is the User Datagram Protocol
(UDP). Both break up a message that an application wants to send into packets and
attempt to deliver those packets to the intended recipient. At the recipient's side,
both take the payload from the received packets and pass those to the application
layer.

The main difference between TCP and UDP is that TCP is reliable and UDP is not. TCP
will collect incoming packets, put them in the right order and thereby reassemble the
original message. If necessary, TCP requests retransmission of lost or damaged
packets. UDP merely takes each incoming packet and delivers the payload (the
original message) to the application layer. Any errors or out-of-order data should be
taken care of by the application.

UDP is much faster than TCP, and so is mainly used for applications like audio and
video streaming, where the occasional error is less important than getting all the data
there at the right time. More generally, UDP is designed for applications that do not
require the packets to be in any specific order. Because of this, UDP is sometimes
called a "connection-less" protocol.

Taking the example of e-mail again, the e-mail client and server communicate over a
reliable TCP connection. The server listens on a certain port (port 25) until a
connection request arrives from the client. The server acknowledges the request, and
a TCP connection is established. Using this connection the client and server can
exchange data.

The content of this data is not really relevant at this level: that's the responsibility of
the application layer. The e-mail message and all the other information exchanged at
that SMTP application layer are merely payload, data that needs to be transported.
Hence the name transport layer.

The Network Layer

The network layer is responsible for transmitting and routing data packets over the
network. The Internet uses the Internet Protocol or IP as its network layer. Each node
on the network has an address, which of course is called the IP address. Data is sent
as IP packets.

A transport layer connection is made up up of a large number of IP packets

exchanged by the client and server. The Internet Protocol (IP) is very simple: a packet
has a source, a destination and a payload, and it's passed from one node in the
network to another until it gets to the destination. The IP does not notice that a
packet gets lost. It just never gets to the destination. If a particular node cannot pass
the packet to the next node along the normal route, it will do its best to find an
alternative path. That's why IP is sometimes called a "best-effort" protocol.

When the client sends its TCP connection request, the network layer puts the request
in a number of packets and transmits each of them to the server. Each packet can
take a different route, and some of the packets may get lost along the way. If they all
make it, the transport layer at the server is able to reconstruct the request, and it will
prepare a response confirming that a TCP connection has been set up. This response
is sent back again in a number of IP packets that will hopefully make it to the client.

The Link Layer

The Internet Protocol basically assumes all computers are part of one very large
"web" of nodes that can all pass packets to other nodes. There's always a route from
one node to another, even if sometimes a very large number of intermediate nodes
get involved. The link layer is what makes this assumption true.

The link layer provides a network connection between hosts on a particular local
network, as well as interconnection between such local networks. The e-mail client
runs on a personal computer in someone's home network, which is set up using the
Ethernet protocol. The link layer now is that Ethernet network. The IP packets that
this computer transmits, are added as payload to Ethernet packets (called "frames")
that are transmitted over the local network to the ADSL modem that connects the
local network to the provider.
 A different kind of link layer protocol is used to transmit the payload taken from
the Ethernet frames from the ADSL modem to the provider. At the provider this
payload is again passed forward using yet another link level protocol. The "web of
nodes" that the Internet Protocol relies on thus actually is made up of a large
number of local networks, each with their own link layer protocol, that each
forward the IP packet by putting it into their own kind of message that is then sent
over the local network.

The Physical Layer

The lowest layer is the physical layer, which defines how the cables, network
cards, wireless transmitters and other hardware connect computers to networks
and networks to the rest of the Internet. Examples of physical layer networks are
Ethernet, WiFi, Token Ring and Fiber Data Distributed Interface (FDDI). Note that
many of these technologies also have their own link layer protocol. Often link and
physical layer are closely related.

The physical layer provides the means to transfer the actual bits from one
computer to another. In an Ethernet network (a link layer protocol), a computer is
connected by plugging a network cable into its Ethernet card, and then plugging
the other end of that cable into a router or switch. The physical layer specifies
how bits of data are sent over that cable: how do the electrical currents or the
pulses the card sends get turned back into the data for the higher level layers. For
wireless networks, this works exactly the same, except of course there is no cable.

ADAPTATION OF TCP WINDOW

The first phase of a TCP session is establishment of the connection. This

requires a three-way handshake, ensuring that both sides of the connection have an
unambiguous understanding of the sequence number space of the remote side for
this session. The operation of the connection is as follows:

 The local system sends the remote end an initial sequence number to the remote
port, using a SYN packet.

 The remote system responds with an ACK of the initial sequence number and the
initial sequence number of the remote end in a response SYN packet.
 The local end responds with an ACK of this remote sequence number.
 The performance implication of this protocol exchange is that it takes one and a
half round-trip times (RTTs) for the two systems to synchronize state before any
data can be sent.

After the connection has been established, the TCP protocol manages the
reliable exchange of data between the two systems. The algorithms that determine
the various retransmission timers have been redefined numerous times. TCP is a
sliding-window protocol, and the general principle of flow control is based on the
management of the advertised window size and the management of retransmission
timeouts, attempting to optimize protocol performance within the observed delay
and loss parameters of the connection.

Tuning a TCP protocol stack for optimal performance over a very low-delay,
high-bandwidth LAN requires different settings to obtain optimal performance over
a dialup Internet connection, which in turn is different for the requirements of a
high-speed wide-area network. Although TCP attempts to discover the delay
bandwidth product of the connection, and attempts to automatically optimize its
flow rates within the estimated parameters of the network path, some estimates will
not be accurate, and the corresponding efforts by TCP to optimize behavior may
not be completely successful.

Another critical aspect is that TCP is an adaptive flow-control protocol.

TCP uses a basic flow-control algorithm of increasing the data-flow rate until the
 network signals that some form of saturation level has been reached (normally
indicated by data loss). When the sender receives an indication of data loss, the
TCP flow rate is reduced; when reliable transmission is reestablished, the flow rate
slowly increases again.

If no reliable flow is reestablished, the flow rate backs further off to an initial probe of
a single packet, and the entire adaptive flow-control process starts again.This process
has numerous results relevant to service quality. First, TCP behaves adaptively , rather
than predictively . The flow-control algorithms are intended to increase the data-flow
rate to fill all available network path capacity, but they are also intended to quickly
back off if the available capacity changes because of interaction with other traffic, or if
a dynamic change occurs in the end-to-end network path.

For example, a single TCP flow across an otherwise idle network attempts to
fill the network path with data, optimizing the flow rate within the available network
capacity. If a second TCP flow opens up across the same path, the two flow-control
algorithms will interact so that both flows will stabilize to use approximately half of
the available capacity per flow. The objective of the TCP algorithms is to adapt so that
the network is fully used whenever one or more data flows are present. In design,
tension always exists between the efficiency of network use and the enforcement of
predictable session performance. With TCP, you give up predictable throughput but
gain a highly utilized, efficient network.
IMPROVEMENT IN TCP PERFORMANCE

The protocols to improve the performance of TCP are:

Link-layer protocols

There have been several proposals for reliable link-layer protocols. The two
main classes of techniques employed by these protocols are: error correction (using
techniques such as forward error correction (FEC)), and retransmission of lost packets
in response to automatic repeat request (ARQ) messages. The link-layer protocols for
the digital cellular systems in the U.S. — both CDMA and TDMA — primarily use
ARQ techniques. While the TDMA protocol guarantees reliable, in-order delivery of
link-layer frames, the CDMA protocol only makes a limited attempt and leaves it to
the (reliable) transport layer to recover from errors in the worst case.
The AIRMAIL protocol employs a combination of FEC and ARQ techniques for loss
recovery. The main advantage of employing a link-layer protocol for loss recovery is
that it fits naturally into the layered structure of network protocols. The link-layer
protocol operates independently of higher-layer protocols (which makes it applicable
to a wide range of scenarios), and consequently, does not maintain any per-connection
state. The main concern about link-layer protocols is the possibility of adverse effect
on certain transport-layer protocols such as TCP.

Indirect-TCP (I-TCP) protocol

This was one of the early protocols to use the split-connection approach. It
involves splitting each TCP connection between a sender and receiver into two
separate connections at the base station — one TCP connection between the sender
and the base station, and the other between the base station and the receiver. In our
classification of protocols, ITCP is a split-connection solution that uses regular TCP
for its connection over wireless link. I-TCP, like other split-connection proposals,
attempts to separate loss recovery over the wireless link from that across the wireline
network, thereby shielding the original TCP sender from the wireless link.

However, as experiments indicate, the choice of TCP over the wireless link
results in several performance problems. Since TCP is not well-tuned for the lossy
link, the TCP sender of the wireless connection often times out, causing the original
sender to stall. In addition, every packet incurs the overhead of going through TCP
protocol processing twice at the base station (as compared to zero times for a non-
split-connection approach), although extra copies are avoided by an efficient kernel
implementation.

Another disadvantage of this approach is that the end-toend semantics of TCP

acknowledgments is violated, since acknowledgments to packets can now reach the
source even before the packets actually reach the mobile host. Also, since this protocol
maintains a significant amount of state at the base station per TCP connection, handoff
procedures tend to be complicated and slow.

The Snoop Protocol

The snoop protocol introduces a module, called the snoop agent, at the base
station. The agent monitors every packet that passes through the TCP connection in
both directions and maintains a cache of TCP segments sent across the link that have
not yet been acknowledged by the receiver. A packet loss is detected by the arrival of a
small number of duplicate acknowledgments from the receiver or by a local timeout.

The snoop agent retransmits the lost packet if it has it cached and suppresses the
duplicate acknowledgments. In classification of protocols, the snoop protocol is a link-
layer protocol that takes advantage of the knowledge of the higher-layer transport
protocol (TCP). The main advantage of this approach is that it suppresses duplicate
acknowledgments for TCP segments lost and retransmitted locally, thereby avoiding
unnecessary fast retransmissions and congestion control invocations by the sender.

The per-connection state maintained by the snoop agent at the base station is
soft, and is not essential for correctness. Like other link-layer solutions, the snoop
approach could also suffer from not being able to completely shield the sender from
wireless losses.

Selective Acknowledgments

Since standard TCP uses a cumulative acknowledgment scheme, it often does

not provide the sender with sufficient information to recover quickly from multiple
packet losses within a single transmission window. Several studies have shown that
TCP enhanced with selective acknowledgments performs better than standard TCP in
such situations. SACKs were added as an option to TCP by RFC 1072. However,
disagreements over the use of SACKs prevented the specification from being adopted,
and the SACK option was removed from later TCP RFCs. Recently, there has been
renewed interest in adding SACKs to TCP.

Two of the more interesting proposals are the TCP SACKs Internet Draft and
the SMART scheme. The Internet Draft proposes that each acknowledgment contain
information about up to three non-contiguous blocks of data that have been received
successfully. Each block of data is described by its starting and ending sequence
number. Due to the limited number of blocks it is best to inform the sender about the
most recent blocks received.

An alternate proposal, SMART, uses acknowledgments that contain the

cumulative acknowledgment and the sequence number of the packet that caused the
receiver to generate the acknowledgment (this information is a subset of the three-
blocks scheme proposed in the Internet Draft). The sender uses these SACKs to create
a bitmask of packets that have been successfully received. This scheme trades off
some resilience to reordering and lost acknowledgments in exchange for a reduction in
overhead to generate and transmit acknowledgments.

UNIT- III

GLOBAL SYSTEM FOR MOBILE

COMMUNICATION (GSM)

GSM stands for Global System for Mobile Communication. It is a digital

cellular technology used for transmitting mobile voice and data services. The concept
of GSM emerged from a cell-based mobile radio system at Bell Laboratories in the
early 1970s. GSM is the name of a standardization group established in 1982 to create
a common European mobile telephone standard.

GSM is the most widely accepted standard in telecommunications and it is

implemented globally.GSM is a circuit-switched system that divides each 200 kHz
channel into eight 25 kHz time-slots. GSM operates on the mobile communication
bands 900 MHz and 1800 MHz in most parts of the world. In the US, GSM operates in
the bands 850 MHz and 1900 MHz.

GSM owns a market share of more than 70 percent of the world's digital
cellular subscribers. GSM makes use of narrowband Time Division Multiple Access
(TDMA) technique for transmitting signals. GSM was developed using digital
technology. It has an ability to carry 64 kbps to 120 Mbps of data rates. Presently
GSM supports more than one billion mobile subscribers in more than 210 countries
throughout the world.
 GSM provides basic to advanced voice and data services including roaming
service. Roaming is the ability to use your GSM phone number in another GSM
network.GSM digitizes and compresses data, then sends it down through a channel
with two other streams of user data, each in its own timeslot.

Why GSM?

Listed below are the features of GSM that account for its popularity and wide
acceptance.

 Improved spectrum efficiency


 International roaming

 Low-cost mobile sets and base stations (BSs)

 High-quality speech

 Compatibility with Integrated Services Digital Network (ISDN) and other

telephone company services

 Support for new services

GSM History

The following table shows some of the important events in the rollout of the GSM
system.
 A GSM network comprises of many functional units. These functions and
interfaces are explained in this chapter. The GSM network can be broadly divided
into:

• The Mobile Station (MS)

• The Base Station Subsystem (BSS)

• The Network Switching Subsystem (NSS)

• The Operation Support Subsystem (OSS)

Given below is a simple pictorial view of the GSM architecture.

 The additional components of the GSM architecture comprise of databases and
messaging systems functions:

 Home Location Register (HLR)


 Visitor Location Register (VLR)

 Equipment Identity Register (EIR)

 Authentication Center (AuC)

 SMS Serving Center (SMS SC)

  Gateway MSC (GMSC)

 Chargeback Center (CBC)

 Transcoder and Adaptation Unit (TRAU)

The following diagram shows the GSM network along with the added elements:

The MS and the BSS communicate across the Um interface. It is also known as
the air interface or the radio link. The BSS communicates with the Network Service
Switching (NSS) center across the A interface.

GSM network areas

In a GSM network, the following areas are defined:

Cell : Cell is the basic service area; one BTS covers one cell. Each cell is given a Cell
Global Identity (CGI), a number that uniquely identifies the cell.
Location Area : A group of cells form a Location Area (LA). This is the area that is
paged when a subscriber gets an incoming call. Each LA is assigned a Location Area
Identity (LAI). Each LA is served by one or more BSCs.

MSC/VLR Service Area : The area covered by one MSC is called the MSC/VLR
service

area.

PLMN : The area covered by one network operator is called the Public Land
Mobile Network (PLMN). A PLMN can contain one or more MSCs.

GSM protocol stack

GSM architecture is a layered model that is designed to allow communications

between two different systems. The lower layers assure the services of the upper-layer
protocols. Each layer passes suitable notifications to ensure the transmitted data has
been formatted, transmitted, and received accurately.

The GMS protocol stacks diagram is shown below:

MS Protocols

Based on the interface, the GSM signalling protocol is assembled into three general
layers:

Layer 1 : The physical layer. It uses the channel structures over the air interface.

Layer 2 : The data-link layer. Across the Um interface, the data-link layer is a
modified version of the Link access protocol for the D channel (LAP-D) protocol used
in ISDN, called Link access protocol on the Dm channel (LAP-Dm). Across the A
interface, the Message Transfer Part (MTP), Layer 2 of SS7 is used.

Layer 3 : GSM signalling protocol‘s third layer is divided into three

sublayers: o Radio Resource Management (RR),

o Mobility Management (MM), and

o Connection Management (CM).

MS to BTS Protocols

The RR layer is the lower layer that manages a link, both radio and fixed,
between the MS and the MSC. For this formation, the main components involved are
the MS, BSS, and MSC. The responsibility of the RR layer is to manage the RR-
session, the time when a mobile is in a dedicated mode, and the radio channels
including the allocation of dedicated channels.

The MM layer is stacked above the RR layer. It handles the functions that arise
from the mobility of the subscriber, as well as the authentication and security aspects.
Location management is concerned with the procedures that enable the system to
know the current location of a powered-on MS so that incoming call routing can be
completed.

The CM layer is the topmost layer of the GSM protocol stack. This layer is responsible
for Call Control, Supplementary Service Management, and Short Message Service
Management. Each of these services are treated as individual layer within the CM
layer. Other functions of the CC sub layer include call establishment, selection of the
type of service (including alternating between services during a call), and call release.

BSC Protocols

The BSC uses a different set of protocols after receiving the data from the BTS.
The Abis interface is used between the BTS and BSC. At this level, the radio
resources at the lower portion of Layer 3 are changed from the RR to the Base
Transceiver Station Management (BTSM). The BTS management layer is a relay
function at the BTS to the BSC.

The RR protocols are responsible for the allocation and reallocation of traffic
channels between the MS and the BTS. These services include controlling the initial
access to the system, paging for MT calls, the handover of calls between cell sites,
power control, and call termination. The BSC still has some radio resource
management in place for the frequency coordination, frequency allocation, and the
management of the overall network layer for the Layer 2 interfaces.
 To transit from the BSC to the MSC, the BSS mobile application part or the
direct application part is used, and SS7 protocols is applied by the relay, so that the
MTP 1-3 can be used as the prime architecture.

MSC Protocols

At the MSC, starting from the BSC, the information is mapped across the A
interface to the MTP Layers 1 through 3. Here, Base Station System Management
Application Part (BSS MAP) is said to be the equivalent set of radio resources. The
relay process is finished by the layers that are stacked on top of Layer 3 protocols,
they are BSS MAP/DTAP, MM, and CM. This completes the relay process.

To find and connect to the users across the network, MSCs interact using the
control-signalling network. Location registers are included in the MSC databases to
assist in the role of determining how and whether connections are to be made to
roaming users.Each GSM MS user is given a HLR that in turn comprises of the user‘s
location and subscribed services.

VLR is a separate register that is used to track the location of a user.

When the users move out of the HLR covered area, the VLR is notified by the
MS to find the location of the user. The VLR in turn, with the help of the control
network, signals the HLR of the MS‘s new location. With the help of location
information contained in the user‘s HLR, the MT calls can be routed to the user.

GSM addressing
GSM treats the users and the equipment in different ways. Phone numbers,
subscribers, and equipment identifiers are some of the known ones. There are many
other identifiers that have been well-defined, which are required for the subscriber‘s
mobility management and for addressing the remaining network elements. Vital
addresses and identifiers that are used in GSM are addressed below.

International Mobile Station Equipment Identity (IMEI)

 The International Mobile Station Equipment Identity (IMEI) looks more like a
serial number which distinctively identifies a mobile station internationally. This is
allocated by the equipment manufacturer and registered by the network operator, who
stores it in the Entrepreneurs-in-Residence (EIR). By means of IMEI, one recognizes
obsolete, stolen, or non-functional equipment.

Following are the parts of IMEI:

 Type Approval Code (TAC) : 6 decimal places, centrally assigned.


 Final Assembly Code (FAC) : 6 decimal places, assigned by the manufacturer.

 Serial Number (SNR) : 6 decimal places, assigned by the manufacturer.

 Spare (SP) : 1 decimal place.

Thus, IMEI = TAC + FAC + SNR + SP. It uniquely characterizes a mobile

station and gives clues about the manufacturer and the date of manufacturing.

International Mobile Subscriber Identity (IMSI)

Every registered user has an original International Mobile Subscriber Identity

(IMSI) with a valid IMEI stored in their Subscriber Identity Module (SIM).

IMSI comprises of the following parts:

 Mobile Country Code (MCC) : 3 decimal places, internationally standardized.


 Mobile Network Code (MNC) : 2 decimal places, for unique identification
of mobile network within the country.

  Mobile Subscriber Identification Number (MSIN) : Maximum 10 decimal
places, identification number of the subscriber in the home mobile network.

Mobile Subscriber ISDN Number (MSISDN)

The authentic telephone number of a mobile station is the Mobile Subscriber

ISDN Number (MSISDN). Based on the SIM, a mobile station can have many
MSISDNs, as each subscriber is assigned with a separate MSISDN to their SIM
respectively.

Listed below is the structure followed by MSISDN categories, as they are

defined based on international ISDN number plan:

Country Code (CC) : Up to 3 decimal places.

 National Destination Code (NDC) : Typically 2-3 decimal places.


 Subscriber Number (SN) : Maximum 10 decimal places.

Mobile Station Roaming Number (MSRN)

Mobile Station Roaming Number (MSRN) is an interim location dependent

ISDN number, assigned to a mobile station by a regionally responsible Visitor
Location Register (VLA). Using MSRN, the incoming calls are channelled to the MS.

The MSRN has the same structure as the MSISDN.

 Country Code (CC) : of the visited network.


 National Destination Code (NDC) : of the visited network.

 Subscriber Number (SN) : in the current mobile network.
Location Area Identity (LAI)

Within a PLMN, a Location Area identifies its own authentic Location Area
Identity (LAI). The LAI hierarchy is based on international standard and structured in
a unique format as mentioned below:

 Country Code (CC) : 3 decimal places.


 Mobile Network Code (MNC) : 2 decimal places.

 Location Area Code (LAC) : maximum 5 decimal places or maximum twice 8
bits coded in hexadecimal (LAC < FFFF).

Temporary Mobile Subscriber Identity (TMSI)

Temporary Mobile Subscriber Identity (TMSI) can be assigned by the VLR,

which is responsible for the current location of a subscriber. The TMSI needs to have
only local significance in the area handled by the VLR. This is stored on the network
side only in the VLR and is not passed to the Home Location Register (HLR).

Together with the current location area, the TMSI identifies a subscriber
uniquely. It can contain up to 4 × 8 bits.

Local Mobile Subscriber Identity (LMSI)

Each mobile station can be assigned with a Local Mobile Subscriber Identity
(LMSI), which is an original key, by the VLR. This key can be used as the auxiliary
searching key for each mobile station within its region. It can also help accelerate the
database access. An LMSI is assigned if the mobile station is registered with the VLR
and sent to the HLR. LMSI comprises of four octets (4x8 bits).

Cell Identifier (CI)

 Using a Cell Identifier (CI) (maximum 2 × 8) bits, the individual cells that are
within an LA can be recognized. When the Global Cell Identity (LAI + CI) calls are
combined, then it is uniquely defined.

GSM security

GSM is the most secured cellular telecommunications system available today.

GSM has its security methods standardized. GSM maintains end-to-end security by
retaining the confidentiality of calls and anonymity of the GSM subscriber.

Temporary identification numbers are assigned to the subscriber‘s number to

maintain the privacy of the user. The privacy of the communication is maintained by
applying encryption algorithms and frequency hopping that can be enabled using
digital systems and signalling.

Mobile Station Authentication

The GSM network authenticates the identity of the subscriber through the use of
a challenge-response mechanism. A 128-bit Random Number (RAND) is sent to the
MS. The MS computes the 32-bit Signed Response (SRES) based on the encryption of
the RAND with the authentication algorithm (A3) using the individual subscriber
authentication key (Ki). Upon receiving the SRES from the subscriber, the GSM
network repeats the calculation to verify the identity of the subscriber.

The individual subscriber authentication key (Ki) is never transmitted over the
radio channel, as it is present in the subscriber's SIM, as well as the AUC, HLR, and
VLR databases. If the received SRES agrees with the calculated value, the MS has
been successfully authenticated and may continue. If the values do not match, the
connection is terminated and an authentication failure is indicated to the MS.

The calculation of the signed response is processed within the SIM. It provides
enhanced security, as confidential subscriber information such as the IMSI or the
individual subscriber authentication key (Ki) is never released from the SIM during
the authentication process.
Signalling and Data Confidentiality

The SIM contains the ciphering key generating algorithm (A8) that is used to
produce the 64-bit ciphering key (Kc). This key is computed by applying the same
random number (RAND) used in the authentication process to ciphering key
generating algorithm (A8) with the individual subscriber authentication key (Ki).

GSM provides an additional level of security by having a way to change the ciphering
key, making the system more resistant to eavesdropping. The ciphering key may be
changed at regular intervals as required. As in case of the authentication
process, the

computation of the ciphering key (Kc) takes place internally within the SIM.
Therefore,

sensitive information such as the individual subscriber authentication key (Ki) is

never

revealed by the SIM.

Encrypted voice and data communications between the MS and the

network is

accomplished by using the ciphering algorithm A5. Encrypted communication is

initiated by

a ciphering mode request command from the GSM network. Upon receipt of this
command,

the mobile station begins encryption and decryption of data using the ciphering
algorithm

(A5) and the ciphering key (Kc).

Subscriber Identity Confidentiality

To ensure subscriber identity confidentiality, the Temporary Mobile

Subscriber

Identity (TMSI) is used. Once the authentication and encryption procedures are done,
the

TMSI is sent to the mobile station. After the receipt, the mobile station responds. The
TMSI

is valid in the location area in which it was issued. For communications outside the
location

area, the Location Area Identification (LAI) is necessary in addition to the TMSI.

GSM Billing

GSM service providers are doing billing based on the services they are
providing to their customers. All the parameters are simple enough to charge a
customer for the provided services.

Telephony Service

These services can be charged on per call basis. The call initiator has to pay the
charges, and the incoming calls are nowadays free. A customer can be charged based
on different parameters such as:

 International call or long distance call.


 Local call.

 Call made during peak hours.

 Call made during night time.

 Discounted call during weekends.

 Call per minute or per second.

 Many more other criteria can be designed by a service provider to charge
their customers.

SMS Service

Most of the service providers charge their customer's SMS services based on the
number of text messages sent. There are other prime SMS services available where
service providers charge more than normal SMS charge. These services are being
availed in collaboration of Television Networks or Radio Networks to demand SMS
from the audiences.

Most of the time, the charges are paid by the SMS sender but for some services
like stocks and share prices, mobile banking facilities, and leisure booking services,
etc. the recipient of the SMS has to pay for the service.

GPRS Services

Using GPRS service, you can browse, play games on the Internet, and download
movies. So a service provider will charge you based on the data uploaded as well as
data downloaded on your mobile phone. These charges will be based on per Kilo Byte
data downloaded/uploaded.

Additional parameter could be a QoS provided to you. If you want to watch a

movie, then a low QoS may work because some data loss may be acceptable, but if
you are downloading a zip file, then a single byte loss will corrupt your complete
downloaded file.Another parameter could be peak and off peak time to download a
data file or to browse the Internet.
Supplementary Services
Most of the supplementary services are being provided based on monthly rental or
absolutely free. For example, call waiting, call forwarding, calling number
identification, and call on hold are available at zero cost.
Call barring is a service, which service providers use just to recover their dues, etc.,
otherwise this service is not being used by any subscriber. Call conferencing service is
a form of simple telephone call where the customers are charged for multiple calls
made at a time. No service provider charges extra charge for this service.
Closed User Group (CUG) is very popular and is mainly being used to give special
discounts to the users if they are making calls to a particular defined group of
subscribers. Advice of Charge (AoC) can be charged based on number of queries
made by a subscriber.

GENERAL PACKET RADIO SERVICE

General Packet Radio System is also known as GPRS is a third-generation
step toward internet access. GPRS is also known as GSM-IP that is a Global-System
Mobile Communications Internet Protocol as it keeps the users of this system online,
allows to make voice calls, and access internet on-the-go. Even Time-Division
Multiple Access (TDMA) users benefit from this system as it provides packet radio
access.
GPRS also permits the network operators to execute an Internet Protocol (IP)
based core architecture for integrated voice and data applications that will continue
to be used and expanded for 3G services.
GPRS supersedes the wired connections, as this system has simplified access to
the packet data networks like the internet. The packet radio principle is employed by
GPRS to transport user data packets in a structure way between GSM mobile stations
and external packet data networks. These packets can be directly routed to the
packet switched networks from the GPRS mobile stations.
In the current versions of GPRS, networks based on the Internet Protocol (IP) like
the global internet or private/corporate intranets and X.25 networks are supported.
Who owns GPRS ?
 The GPRS specifications are written by the European Telecommunications
Standard Institute (ETSI), the European counterpart of the American National
Standard Institute (ANSI).
Key Features
Following three key features describe wireless packet data:
 The always online feature - Removes the dial-up process, making applications
only one click away.

 An upgrade to existing systems - Operators do not have to replace their

equipment; rather, GPRS is added on top of the existing infrastructure.

 An integral part of future 3G systems - GPRS is the packet data core

network for 3G systems EDGE and WCDMA.
Goals of GPRS
GPRS is the first step toward an end-to-end wireless infrastructure and has the
following goals:
 Open architecture
  Consistent IP services
  Same infrastructure for different air interfaces
  Integrated telephony and Internet infrastructure
  Leverage industry investment in IP
  Service innovation independent of infrastructure
Benefits of GPRS
Higher Data Rate
GPRS benefits the users in many ways, one of which is higher data rates in turn of
shorter access times. In the typical GSM mobile, setup alone is a lengthy process and
equally, rates for data permission are restrained to 9.6 kbit/s. The session
establishment time offered while GPRS is in practice is lower than one second and
ISDN-line data rates are up to many 10 kbit/s.
Easy Billing
GPRS packet transmission offers a more user-friendly billing than that offered by
circuit switched services. In circuit switched services, billing is based on the duration
of the connection. This is unsuitable for applications with bursty traffic. The user
must pay for the entire airtime, even for idle periods when no packets are sent (e.g.,
when the user reads a Web page).
In contrast to this, with packet switched services, billing can be based on the
amount of transmitted data. The advantage for the user is that he or she can be
"online" over a long period of time but will be billed based on the transmitted data
volume.
GPRS Architecture
GPRS architecture works on the same procedure like GSM network, but, has
additional entities that allow packet data transmission. This data network overlaps a
second-generation GSM network providing packet data transport at the rates from
9.6 to 171 kbps. Along with the packet data transport the GSM network
accommodates multiple users to share the same air interface resources concurrently.
Following is the GPRS Architecture diagram:

GPRS attempts to reuse the existing GSM network elements as much as

possible, but to effectively build a packet-based mobile cellular network, some new
network elements, interfaces, and protocols for handling packet traffic are required.
Therefore, GPRS requires modifications to numerous GSM network elements as
summarized below:
GPRS Mobile Stations
New Mobile Stations (MS) are required to use GPRS services because existing GSM
phones do not handle the enhanced air interface or packet data. A variety of MS can
exist, including a high-speed version of current phones to support high-speed data
access, a new PDA device with an embedded GSM phone, and PC cards for
 laptop computers. These mobile stations are backward compatible for
making voice calls using GSM.

GPRS Base Station Subsystem

Each BSC requires the installation of one or more Packet Control Units (PCUs) and
a software upgrade. The PCU provides a physical and logical data interface to the
Base Station Subsystem (BSS) for packet data traffic. The BTS can also require a
software upgrade but typically does not require hardware enhancements.
When either voice or data traffic is originated at the subscriber mobile, it is
transported over the air interface to the BTS, and from the BTS to the BSC in the
same way as a standard GSM call. However, at the output of the BSC, the traffic is
separated; voice is sent to the Mobile Switching Center (MSC) per standard GSM, and
data is sent to a new device called the SGSN via the PCU over a Frame Relay
interface.
GPRS Support Nodes
Following two new components, called Gateway GPRS Support Nodes (GSNs) and,
Serving GPRS Support Node (SGSN) are added:
Gateway GPRS Support Node (GGSN)
The Gateway GPRS Support Node acts as an interface and a router to external
networks. It contains routing information for GPRS mobiles, which is used to tunnel
packets through the IP based internal backbone to the correct Serving GPRS Support
Node. The GGSN also collects charging information connected to the use of the
external data networks and can act as a packet filter for incoming traffic.
Serving GPRS Support Node (SGSN)
The Serving GPRS Support Node is responsible for authentication of GPRS mobiles,
registration of mobiles in the network, mobility management, and collecting
information on charging for the use of the air interface.
Internal Backbone
The internal backbone is an IP based network used to carry packets between
different GSNs. Tunnelling is used between SGSNs and GGSNs, so the internal
backbone does not need any information about domains outside the GPRS network.
Signalling from a GSN to a MSC, HLR or EIR is done using SS7.
Routing Area
 GPRS introduces the concept of a Routing Area. This concept is similar to
Location Area in GSM, except that it generally contains fewer cells. Because routing
areas are smaller than location areas, less radio resources are used while
broadcasting a page message.
GPRS Protocol Stack
The flow of GPRS protocol stack and end-to-end message from MS to the GGSN is
displayed in the below diagram. GTP is the protocol used between the SGSN and
GGSN using the Gn interface. This is a Layer 3 tunnelling protocol.

The process that takes place in the application looks like a normal IP sub-network
for the users both inside and outside the network. The vital thing that needs
attention is, the application communicates via standard IP, that is carried through the
GPRS network and out through the gateway GPRS. The packets that are mobile
between the GGSN and the SGSN use the GPRS tunnelling protocol, this way the IP
addresses located on the external side of the GPRS network do not have deal with
the internal backbone. UDP and IP are run by GTP.
SubNetwork Dependent Convergence Protocol (SNDCP) and Logical Link Control
(LLC) combination used in between the SGSN and the MS. The SNDCP flattens data to
reduce the load on the radio channel. A safe logical link by encrypting packets is
provided by LLC and the same LLC link is used as long as a mobile is under a single
SGSN.
In case, the mobile moves to a new routing area that lies under a different SGSN;
then, the old LLC link is removed and a new link is established with the new Serving
GSN X.25. Services are provided by running X.25 on top of TCP/IP in the internal
backbone.
GPRS Applications
GPRS has opened a wide range of unique services to the mobile wireless
subscriber. Some of the characteristics that have opened a market full of enhanced
value services to the users. Below are some of the characteristics:
 Mobility - The ability to maintain constant voice and data communications
while on the move.
  Immediacy - Allows subscribers to obtain connectivity when needed,
regardless of location and without a lengthy login session.
  Localization - Allows subscribers to obtain information relevant to their
current location.
  Using the above three characteristics varied possible applications are being
developed to offer to the mobile subscribers. These applications, in general, can be
divided into two high-level categories:
o Corporation
o Consumer
These two levels further include:
 Communications - E-mail, fax, unified messaging and intranet/internet access,
etc.
 Value-added services - Information services and games, etc.
 E-commerce - Retail, ticket purchasing, banking and financial trading, etc.
 Location-based applications - Navigation, traffic conditions, airline/rail
schedules and location finder, etc.
 Vertical applications - Freight delivery, fleet management and sales-
force automation.
 Advertising - Advertising may be location sensitive. For example, a user
entering a mall can receive advertisements specific to the stores in that mall.
Along with the above applications, non-voice services like SMS, MMS and voice
calls are also possible with GPRS. Closed User Group (CUG) is a common term used
after GPRS is in the market, in addition, it is planned to implement supplementary
services, such as Call Forwarding Unconditional (CFU), and Call Forwarding on Mobile
subscriber Not Reachable (CFNRc), and closed user group (CUG).
GPRS Quality Of Service
Quality of Service (QoS) requirements of conventional mobile packet data
applications are in assorted forms. The QoS is a vital feature of GPRS services as there
are different QoS support requirements for assorted GPRS applications like realtime
multimedia, web browsing, and e-mail transfer.
GPRS allows defining QoS profiles using the following parameters :
 Service Precedence
  Reliability
  Delay and
  Throughput
These parameters are described below:
Service Precedence
The preference given to a service when compared to another service is known
as Service Precedence. This level of priority is classified into three levels called:
 high
  normal
  low
When there is network congestion, the packets of low priority are discarded as
compared to high or normal priority packets.
Reliability
This parameter signifies the transmission characteristics required by an
application. The reliability classes are defined which guarantee certain maximum
values for the probability of loss, duplication, mis-sequencing, and corruption of
packets.
Delay
The delay is defined as the end-to-end transfer time between
two communicating mobile stations or between a mobile station and the GI
interface to an external packet data network.

This includes all delays within the GPRS network, e.g., the delay for request and
assignment of radio resources and the transit delay in the GPRS backbone network.
Transfer delays outside the GPRS network, e.g., in external transit networks, are not
taken into account.
Throughput
The throughput specifies the maximum/peak bit rate and the mean bit rate.
Using these QoS classes, QoS profiles can be negotiated between the mobile user and
the network for each session, depending on the QoS demand and the available
resources. The billing of the service is then based on the transmitted data volume,
the type of service, and the chosen QoS profile.
GPRS Mobile Station Class
Mobile Station Classes talk about the globally-known equipment handset which is
also known as Mobile Station (MS) and its three different classes. This equipment,
more popular as handset, is used to make phone calls and access data services. The
MS comprises of Terminal Equipment (TE) and Mobile Terminal (MT).
TE is the equipment that accommodates the applications and the user interaction,
while the MT is the part that connects to the network.
In the following example, Palm Pilot is TE and Mobile phone is MT.

In order to take advantage of the new GPRS services, we need new GPRS
enabled handsets. There are three different classes of GPRS terminal equipments:

Class A
 Class A terminals can manage both packet data and voice simultaneously.
Which means, one needs two transceivers, as the handset has to send or receive data
and voice at the same time. This is the main reason why class A terminals are high-
priced to manufacture than class B and C terminals.
Class B
Class B terminals do not play the same role like Class A. These terminals can
manage either packet data or voice at a time. One can use a single transceiver for
both, resulting in the low cost of terminals.
For example, If a user is using the GPRS session (like WAP browsing, file transfer, etc.)
then this session is halted if he or she receives a call. This terminal does not allow
both the sessions active in one go. This backlog needs rectification thereby giving the
user a facility of both receiving a call and maintaining the data session.
Class C
Class C terminals can manage either only packet data or only voice. Examples
of class C terminals are GPRS PCM/CIA cards, embedded modules in vending
machines, and so on. Due to the high cost of class A handsets, most handset
manufacturers have announced that their first handsets will be class B. Currently,
work is going on in 3GPP to standardize a light weight class A in order to make
handsets with simultaneous voice and data available at a reasonable cost.
GPRS Access Mode
The GPRS access modes specify whether or not the GGSN requests user
authentication at the access point to a Public Data Network (PDN). The available
options are:
 Transparent - No security authorization/authentication is requested by the GGSN.
 Non-transparent - In this case, GGSN acts as a proxy for authenticating.
The GPRS transparent and non-transparent modes relate only to PDP type IPv4.
Transparent Mode
Transparent access pertains to a GPRS PLMN that is not involved in subscriber
access authorization and authentication. Access to PDN-related security procedures
are transparent to GSNs. In transparent access mode, the MS is given an address
belonging to the operator or any other addressing space of domain. The address is
given either at subscription as a static address or at PDP context activation, as a
dynamic address.
The dynamic address is allocated from a Dynamic Host Configuration Protocol
(DHCP) server in the GPRS network. Any user authentication is done within the GPRS
network. No RADIUS authentication is performed; only IMSI-based authentication
(from the subscriber identity module in the handset) is done.
Non Transparent Mode
Non-transparent access to an intranet/ISP means that the PLMN plays a role in
the intranet/ISP authentication of the MS. Non-transparent access uses the Password
Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol
(CHAP) message issued by the mobile terminal and piggybacked in the GTP PDP
context activation message. This message is used to build a RADIUS request toward
the RADIUS server associated with the access point name (APN).
GPRS Access Point Name
The GPRS standards define a network identity called an Access Point Name (APN).
An APN identifies a PDN that is accessible from a GGSN node in a GPRS network. In
GPRS, only the APN is used to select the target network. To configure an APN, the
operator configures three elements on the GSN node:
 Access point - Defines an APN and its associated access characteristics,
including security (RADIUS), dynamic address allocation (DHCP), and DNS services.
 Access point list - Defines a logical interface that is associated with the virtual
template.
 Access group - Defines whether access is permitted between the PDN and the
MS.
GPRS Billing
As packet data is introduced into mobile systems, the question of how to bill for
the services arises. Always online and paying by the minute does not sound all that
appealing. Here, we describe the possibilities but it totally depends on different
service providers, how they want to charge their customers.

The SGSN and GGSN register all possible aspects of a GPRS user's behaviour
and generate billing information accordingly. This information is gathered in so-
called Charging Data Records (CDR) and is delivered to a billing gateway.

The GPRS service charging can be based on the following parameters:

 Volume - The amount of bytes transferred, i.e., downloaded and uploaded.

  Duration - The duration of a PDP context session.

 Time - Date, time of day, and day of the week (enabling lower tariffs at off
peak hours).

 Final destination - A subscriber could be charged for access to the specific
network, such as through a proxy server.

 Location - The current location of the subscriber.

 Quality of Service - Pay more for higher network priority.

 SMS - The SGSN will produce specific CDRs for SMS.


 Served IMSI/subscriber - Different subscriber classes (different tariffs for
frequent users, businesses, or private users).

 Reverse charging - The receiving subscriber is not charged for the received
data; instead, the sending party is charged.

 Free of charge - Specified data to be free of charge.

 Flat rate - A fixed monthly fee.

 Bearer service - Charging based on different bearer services (for an operator
who has several networks, such as GSM900 and GSM1800, and who wants to
promote usage of one of the networks). Or, perhaps the bearer service would
be good for areas where it would be cheaper for the operator to offer services
from a wireless LAN rather than from the GSM network.

GENERAL PACKET RADIO SERVICE

 General Packet Radio System is also known as GPRS is a third-generation
step toward internet access. GPRS is also known as GSM-IP that is a Global-System
Mobile Communications Internet Protocol as it keeps the users of this system online,
allows to make voice calls, and access internet on-the-go. Even Time-Division
Multiple Access (TDMA) users benefit from this system as it provides packet radio
access.

GPRS also permits the network operators to execute an Internet Protocol (IP)
based core architecture for integrated voice and data applications that will continue
to be used and expanded for 3G services.

GPRS supersedes the wired connections, as this system has simplified access to
the packet data networks like the internet. The packet radio principle is employed by
GPRS to transport user data packets in a structure way between GSM mobile stations
and external packet data networks. These packets can be directly routed to the
packet switched networks from the GPRS mobile stations.

In the current versions of GPRS, networks based on the Internet Protocol (IP)
like the global internet or private/corporate intranets and X.25 networks are
supported.

Who owns GPRS ?

The GPRS specifications are written by the European Telecommunications

Standard Institute (ETSI), the European counterpart of the American National
Standard Institute (ANSI).

Key Features

Following three key features describe wireless packet data:

 The always online feature - Removes the dial-up process, making applications
only one click away.

 An upgrade to existing systems - Operators do not have to replace their
equipment; rather, GPRS is added on top of the existing infrastructure.

 An integral part of future 3G systems - GPRS is the packet data core network for
3G systems EDGE and WCDMA.

Goals of GPRS

GPRS is the first step toward an end-to-end wireless infrastructure and has the
following goals:

 Open architecture

 Consistent IP services

 Same infrastructure for different air interfaces

 Integrated telephony and Internet infrastructure

 Leverage industry investment in IP

 Service innovation independent of infrastructure

Benefits of GPRS

Higher Data Rate

GPRS benefits the users in many ways, one of which is higher data rates in turn
of shorter access times. In the typical GSM mobile, setup alone is a lengthy process
and equally, rates for data permission are restrained to 9.6 kbit/s. The session
establishment time offered while GPRS is in practice is lower than one second and
ISDN-line data rates are up to many 10 kbit/s.

Easy Billing

GPRS packet transmission offers a more user-friendly billing than that offered
by circuit switched services. In circuit switched services, billing is based on the
duration of the connection. This is unsuitable for applications with bursty traffic. The
user must pay for the entire airtime, even for idle periods when no packets are sent
(e.g., when the user reads a Web page).

In contrast to this, with packet switched services, billing can be based on the
amount of transmitted data. The advantage for the user is that he or she can be
"online" over a long period of time but will be billed based on the transmitted data
volume.

GPRS Architecture

GPRS architecture works on the same procedure like GSM network, but, has
additional entities that allow packet data transmission. This data network overlaps a
second-generation GSM network providing packet data transport at the rates from
9.6 to 171 kbps. Along with the packet data transport the GSM network
accommodates multiple users to share the same air interface resources concurrently.

Following is the GPRS Architecture diagram:

 GPRS attempts to reuse the existing GSM network elements as much as
possible, but to effectively build a packet-based mobile cellular network, some new
network elements, interfaces, and protocols for handling packet traffic are required.

Therefore, GPRS requires modifications to numerous GSM network elements as

summarized below:
GPRS Mobile Stations
New Mobile Stations (MS) are required to use GPRS services because existing GSM
phones do not handle the enhanced air interface or packet data. A variety of MS can
exist, including a high-speed version of current phones to support high-speed data
access, a new PDA device with an embedded GSM phone, and PC cards for
 laptop computers. These mobile stations are backward compatible for
making voice calls using GSM.

GPRS Base Station Subsystem

Each BSC requires the installation of one or more Packet Control Units (PCUs)
and a software upgrade. The PCU provides a physical and logical data interface to
the Base Station Subsystem (BSS) for packet data traffic. The BTS can also require a
software upgrade but typically does not require hardware enhancements.

When either voice or data traffic is originated at the subscriber mobile, it is

transported over the air interface to the BTS, and from the BTS to the BSC in the
same way as a standard GSM call. However, at the output of the BSC, the traffic is
separated; voice is sent to the Mobile Switching Center (MSC) per standard GSM,
and data is sent to a new device called the SGSN via the PCU over a Frame Relay
interface.

GPRS Support Nodes

Following two new components, called Gateway GPRS Support Nodes (GSNs)
and, Serving GPRS Support Node (SGSN) are added:

Gateway GPRS Support Node (GGSN)

The Gateway GPRS Support Node acts as an interface and a router to external
networks. It contains routing information for GPRS mobiles, which is used to tunnel
packets through the IP based internal backbone to the correct Serving GPRS Support
Node. The GGSN also collects charging information connected to the use of the
external data networks and can act as a packet filter for incoming traffic.
Serving GPRS Support Node (SGSN)
 The Serving GPRS Support Node is responsible for authentication of GPRS
mobiles, registration of mobiles in the network, mobility management, and collecting
information on charging for the use of the air interface.

Internal Backbone

The internal backbone is an IP based network used to carry packets between

different GSNs. Tunnelling is used between SGSNs and GGSNs, so the internal
backbone does not need any information about domains outside the GPRS network.
Signalling from a GSN to a MSC, HLR or EIR is done using SS7.

Routing Area

GPRS introduces the concept of a Routing Area. This concept is similar to

Location Area in GSM, except that it generally contains fewer cells. Because routing
areas are smaller than location areas, less radio resources are used while
broadcasting a page message.

GPRS Protocol Stack

The flow of GPRS protocol stack and end-to-end message from MS to the GGSN is
displayed in the below diagram. GTP is the protocol used between the SGSN and
GGSN using the Gn interface. This is a Layer 3 tunnelling protocol.
The process that takes place in the application looks like a normal IP sub-network for
the users both inside and outside the network. The vital thing that needs attention is,
the application communicates via standard IP, that is carried through the GPRS
network and out through the gateway GPRS. The packets that are mobile between
the GGSN and the SGSN use the GPRS tunnelling protocol, this way the IP addresses
located on the external side of the GPRS network do not have deal with the internal
backbone. UDP and IP are run by GTP.

SubNetwork Dependent Convergence Protocol (SNDCP) and Logical Link

Control (LLC) combination used in between the SGSN and the MS. The SNDCP flattens
data to reduce the load on the radio channel. A safe logical link by encrypting
packets is provided by LLC and the same LLC link is used as long as a mobile is under
a single SGSN.

In case, the mobile moves to a new routing area that lies under a different
SGSN; then, the old LLC link is removed and a new link is established with the new
Serving GSN X.25. Services are provided by running X.25 on top of TCP/IP in the
internal backbone.

GPRS Applications
 GPRS has opened a wide range of unique services to the mobile wireless
subscriber. Some of the characteristics that have opened a market full of enhanced
value services to the users. Below are some of the characteristics:

 Mobility - The ability to maintain constant voice and data communications

while on the move.

 Immediacy - Allows subscribers to obtain connectivity when needed,
regardless of location and without a lengthy login session.

 Localization - Allows subscribers to obtain information relevant to their
current location.

 Using the above three characteristics varied possible applications are being
developed to offer to the mobile subscribers. These applications, in general,
can be divided into two high-level categories:
o Corporation

o Consumer

These two levels further include:

 Communications - E-mail, fax, unified messaging and intranet/internet access,

etc.

 Value-added services - Information services and games, etc.

 E-commerce - Retail, ticket purchasing, banking and financial trading, etc.

 Location-based applications - Navigation, traffic conditions, airline/rail
schedules and location finder, etc.
  Vertical applications - Freight delivery, fleet management and sales-
force automation.

 Advertising - Advertising may be location sensitive. For example, a user

entering a

mall can receive advertisements specific to the stores in that mall.

Along with the above applications, non-voice services like SMS, MMS and voice
calls are also possible with GPRS. Closed User Group (CUG) is a common term used
after GPRS is in the market, in addition, it is planned to implement supplementary
services, such as Call Forwarding Unconditional (CFU), and Call Forwarding on Mobile
subscriber Not Reachable (CFNRc), and closed user group (CUG).

GPRS Quality Of Service

Quality of Service (QoS) requirements of conventional mobile packet data

applications are in assorted forms. The QoS is a vital feature of GPRS services as
there are different QoS support requirements for assorted GPRS applications like
realtime multimedia, web browsing, and e-mail transfer.

GPRS allows defining QoS profiles using the following parameters :

 Service Precedence

 Reliability

 Delay and

  Throughput

These parameters are described below:

Service Precedence

The preference given to a service when compared to another service is known

as Service Precedence. This level of priority is classified into three levels called:

 high

 normal

 low

When there is network congestion, the packets of low priority are discarded as
compared to high or normal priority packets.

Reliability

This parameter signifies the transmission characteristics required by an

application. The reliability classes are defined which guarantee certain maximum
values for the probability of loss, duplication, mis-sequencing, and corruption of
packets.

Delay

The delay is defined as the end-to-end transfer time between

two communicating mobile stations or between a mobile station and the GI
interface to an external packet data network.
 This includes all delays within the GPRS network, e.g., the delay for request and
assignment of radio resources and the transit delay in the GPRS backbone network.
Transfer delays outside the GPRS network, e.g., in external transit networks, are not
taken into account.

Throughput

The throughput specifies the maximum/peak bit rate and the mean bit rate.
Using these QoS classes, QoS profiles can be negotiated between the mobile user
and the network for each session, depending on the QoS demand and the available
resources. The billing of the service is then based on the transmitted data volume,
the type of service, and the chosen QoS profile.

GPRS Mobile Station Class

Mobile Station Classes talk about the globally-known equipment handset which
is also known as Mobile Station (MS) and its three different classes. This equipment,
more popular as handset, is used to make phone calls and access data services. The
MS comprises of Terminal Equipment (TE) and Mobile Terminal (MT).

TE is the equipment that accommodates the applications and the user

interaction, while the MT is the part that connects to the network.

In the following example, Palm Pilot is TE and Mobile phone is MT.

 In order to take advantage of the new GPRS services, we need new GPRS
enabled handsets. There are three different classes of GPRS terminal equipments:

Class A

Class A terminals can manage both packet data and voice simultaneously. Which
means, one needs two transceivers, as the handset has to send or receive data
and voice at the same time. This is the main reason why class A terminals are
high-priced to manufacture than class B and C terminals.

Class B

Class B terminals do not play the same role like Class A. These terminals can
manage either packet data or voice at a time. One can use a single transceiver for
both, resulting in the low cost of terminals.

For example, If a user is using the GPRS session (like WAP browsing, file
transfer, etc.) then this session is halted if he or she receives a call. This terminal
does not allow both the sessions active in one go. This backlog needs rectification
 thereby giving the user a facility of both receiving a call and maintaining the data
session.

Class C

Class C terminals can manage either only packet data or only voice.
Examples of class C terminals are GPRS PCM/CIA cards, embedded modules in
vending machines, and so on. Due to the high cost of class A handsets, most
handset manufacturers have announced that their first handsets will be class B.
Currently, work is going on in 3GPP to standardize a light weight class A in order
to make handsets with simultaneous voice and data available at a reasonable
cost.

GPRS Access Mode

The GPRS access modes specify whether or not the GGSN requests user
authentication at the access point to a Public Data Network (PDN). The available
options are:

 Transparent - No security authorization/authentication is requested by the

GGSN.

 Non-transparent - In this case, GGSN acts as a proxy for authenticating.

The GPRS transparent and non-transparent modes relate only to PDP type IPv4.

Transparent Mode

Transparent access pertains to a GPRS PLMN that is not involved in

subscriber access authorization and authentication. Access to PDN-related
security procedures are transparent to GSNs. In transparent access mode, the MS
is given an address belonging to the operator or any other addressing space of
 domain. The address is given either at subscription as a static address or at PDP
context activation, as a dynamic address.

The dynamic address is allocated from a Dynamic Host Configuration Protocol (DHCP)
server in the GPRS network. Any user authentication is done within the GPRS
network. No RADIUS authentication is performed; only IMSI-based authentication
(from the subscriber identity module in the handset) is done.
Non Transparent Mode

Non-transparent access to an intranet/ISP means that the PLMN plays a role in

the intranet/ISP authentication of the MS. Non-transparent access uses the Password
Authentication Protocol (PAP) or Challenge Handshake Authentication Protocol
(CHAP) message issued by the mobile terminal and piggybacked in the GTP PDP
context activation message. This message is used to build a RADIUS request toward
the RADIUS server associated with the access point name (APN).

GPRS Access Point Name

The GPRS standards define a network identity called an Access Point Name
(APN). An APN identifies a PDN that is accessible from a GGSN node in a GPRS
network. In GPRS, only the APN is used to select the target network. To configure an
APN, the operator configures three elements on the GSN node:

 Access point - Defines an APN and its associated access characteristics,

including security (RADIUS), dynamic address allocation (DHCP), and DNS services.

 Access point list - Defines a logical interface that is associated with the virtual
template.

 Access group - Defines whether access is permitted between the PDN and the MS.

GPRS Billing
 As packet data is introduced into mobile systems, the question of how to bill
for the services arises. Always online and paying by the minute does not sound all
that appealing. Here, we describe the possibilities but it totally depends on different
service providers, how they want to charge their customers.

The SGSN and GGSN register all possible aspects of a GPRS user's behaviour
and generate billing information accordingly. This information is gathered in so-
called Charging Data Records (CDR) and is delivered to a billing gateway.

The GPRS service charging can be based on the following parameters:

 Volume - The amount of bytes transferred, i.e., downloaded and uploaded.


 Duration - The duration of a PDP context session.

 Time - Date, time of day, and day of the week (enabling lower tariffs at off
peak hours).

 Final destination - A subscriber could be charged for access to the specific
network, such as through a proxy server.

 Location - The current location of the subscriber.

 Quality of Service - Pay more for higher network priority.

 SMS - The SGSN will produce specific CDRs for SMS.


 Served IMSI/subscriber - Different subscriber classes (different tariffs for
frequent users, businesses, or private users).

  Reverse charging - The receiving subscriber is not charged for the received
data; instead, the sending party is charged.

 Free of charge - Specified data to be free of charge.

 Flat rate - A fixed monthly fee.

 Bearer service - Charging based on different bearer services (for an operator
who has several networks, such as GSM900 and GSM1800, and who wants to
promote usage of one of the networks). Or, perhaps the bearer service would
be good for areas where it would be cheaper for the operator to offer services
from a wireless LAN rather than from the GSM network.

UNIVERSAL MOBILE TELECOMMUNICATION SYSTEM

The Universal Mobile Telecommunications System (UMTS) is a third generation

mobile cellular system for networks based on the GSM standard. Developed and
maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component
of the Standard International Union all IMT-2000 telecommunications and compares
it with the standard set for CDMA2000 networks based on competition cdma One
technology. UMTS uses wideband code division multiple access (W-
CDMA) radio access technology to provide greater spectral efficiency and
bandwidth mobile network operators.

Network Evolution
An Evolution that Makes Sense
HSUPA : High Speed Uplink Packet Access

HSDPA : High speed downlink packet access

The main idea behind 3G is to prepare a universal infrastructure able to carry

existing and also future services. The infrastructure should be so designed that
technology changes and evolution can be adapted to the network without causing
uncertainties to the existing services using the existing network structure.

WCDMA Technology

The first Multiple Access Third Generation Partnership Project (3GPP)

Wideband Code Division networks (WCDMA) were launched in 2002. At the end of
2005, there were 100 WCDMA networks open and a total of more than 150
operators with licenses for frequencies WCDMA operation. Currently, WCDMA
networks are deployed in UMTS band of around 2 GHz in Europe and Asia, including
Japan and America Korea.

WCDMA is deployed in the 850 and 1900 of the existing frequency allocations
and the new 3G band 1700/2100 should be available in the near future. 3GPP has
defined WCDMA operation for several additional bands, which are expected to be
commissioned in the coming years. As WCDMA mobile penetration increases, it
allows WCDMA networks to carry a greater share of voice and data traffic.

WCDMA technology provides some advantages for the operator in that it allows the
data, but also improves the voice of base. Voice capacity offered is very high due to
interference control mechanisms, including frequency reuse of 1, fast power control,
and soft handover. WCDMA can offer a lot more voice minutes to customers.
Meanwhile WCDMA can also improve broadband voice service with AMR codec,
which clearly provides better voice quality than fixed telephone landline. In short,
WCDMA can offer more voice minutes with better quality.

In addition to the high spectral efficiency, third-generation (3G) WCDMA

provides even more dramatic change in capacity of the base station and the
efficiency of the equipment. The high level of integration in the WCDMA is achieved
due to the broadband carrier: a large number of users supported by the carrier, and
less radio frequency (RF) carriers are required to provide the same capacity.

With less RF parts and more digital baseband processing, WCDMA can take
advantage of the rapid evolution of digital signal processing capability. The level of
integration of the high base station enables efficient building high capacity sites since
the complexity of RF combiners, additional antennas or power cables can be avoided.
WCDMA operators are able to provide useful data services, including navigation,
person to person video calls, sports and video and new mobile TV clips.

WCDMA enables simultaneous voice and data which allows, for example,
browsing or email when voice conferencing or video sharing in real time during voice
calls.

The operators also offer mobile connectivity to the Internet and corporate intranet
with maximum bit rate of 384 kbps downlink and both uplink. The first terminals and
networks have been limited to 64 to 128 kbps uplink while the latter products
provide 384 kbps uplink.

HSPA Standardization

High-speed downlink packet access (HSDPA) was standardized as part of 3GPP

Release 5 with the first specification version in March 2002. High-speed uplink packet
access (HSUPA) was part of 3GPP Release 6 with the first specification version in
December 2004. HSDPA and HSUPA together are called High-Speed Packet Access‘

(HSPA).

The first commercial HSDPA networks were available at the end of 2005 and
the commercial HSUPA networks were available on 2007. The HSDPA peak data rate
available in the terminals is initially 1.8Mbps and will increase to 3.6 and 7.2 Mbps
during 2006 and 2007, and later on 10Mbps and beyond 10Mbps. The HSUPA peak
data rate in the initial phase was 1–2 Mbps and the second phase was 3–4Mbps.
 HSPA is deployed over the WCDMA network on the same carrier or - for high
capacity and high speed solution - using another carrier. In both cases, WCDMA and
HSPA can share all the network elements in the core network and the radio network
comprising base stations, radio network controller (RNC), Serving GPRS Support
Node (SGSN) and the Gateway GPRS Support Node (GGSN). WCDMA and HSPA also
share the site base station antennas and antenna cables.

The upgrade WCDMA HSPA requires new software and potentially new
equipment in the base station and RNC to support the rate and higher data capacity.
Because of the shared infrastructure between WCDMA and HSPA, the cost of the
upgrade WCDMA HSPA is very low compared to the construction of a new stand-
alone data network.

UMTS - Radio Interface and Radio Network Aspects

After the introduction of UMTS the amount of wide area data transmission by
mobile users had picked up. But for the local wireless transmissions such as WLAN
and DSL, technology has increased at a much higher rate. Hence, it was important to
consider the data transmission rates equal to the category of fixed line broadband,
when WIMAX has already set high targets for transmission rates. It was clear that the
new 3GPP radio technology Evolved UTRA (E-UTRA, synonymous with the LTE radio
interface) had to become strongly competitive in all respect and for that following
target transmission rates were defined:

 Downlink: 100 Mb/s


 Uplink: 50 Mb/s

Above numbers are only valid for a reference configuration of two antennas for
reception and one transmit antenna in the terminal, and within a 20 MHz spectrum
allocation.

UMTS – All IP Vision

A very general principle was set forth for the Evolved 3GPP system. It should
―all IP‖, means that the IP connectivity is the basic service which is provided to the
users. All other layer services like voice, video, messaging, etc. are built on that.
Looking at the protocol stacks for interfaces between the network nodes, it is clear
that simple model of IP is not applicable to a mobile network.

There are virtual layers in between, which is not applicable to a mobile

network. There are virtual layer in between, in the form of ―tunnels‖, providing the
three aspects - mobility, security, and quality of service. Resulting, IP based protocols
appear both on the transport layer (between network nodes) and on higher layers.

UMTS – Requirements of the New Architecture

 There is a new architecture that covers good scalability, separately for user
plane and control plane. There is a need for different types of terminal mobility
support that are: fixed, nomadic, and mobile terminals. The minimum transmission
and signalling overhead especially in air, in an idle mode of the dual mode UE
signalling should be minimized, in the radio channel multicast capability.

It is required to be reused or extended, as roaming and network sharing

restrictions, compatible with traditional principles established roaming concept,
quite naturally, the maximum transmission delay required is equivalent to the fixed
network, specifically less than 5 milliseconds, set to control plane is less than 200
milliseconds delay target.

Looking at the evolution of the 3GPP system in full, it may not seem less
complex than traditional 3GPP system, but this is due to the huge increase in
functionality. Another strong desire is to arrive at a flat structure, reducing
CAPEX/OPEX for operators in the 3GPP architecture carriers.

Powerful control functions should also be maintained with the new 3GPP
systems, both real-time seamless operation (for example, VoIP) and non-real-time
applications and services. The system should perform well for VoIP services in both
the scenarios. Special attention is also paid to the seamless continuity with legacy
systems (3GPP and 3GPP2), supports the visited network traffic local breakout of
voice communications.

UMTS – Security and Privacy

Visitor Location Register (VLR) and SNB are used to keep track of all the mobile
stations that are currently connected to the network. Each subscriber can be
identified by its International Mobile Subscriber Identity (IMSI). To protect against
profiling attacks, the permanent identifier is sent over the air interface as
infrequently as possible. Instead, local identities Temporary Mobile Subscriber force
(TMSI) is used to identify a subscriber whenever possible.

Each UMTS subscriber has a dedicated home network with which it shares a
secret key Ki long term. The Home Location Register (HLR) keeps track of the current
location of all the home network subscribers. Mutual authentication between a
mobile station and a visited network is carried out with the support of the current
GSN (SGSN) and the MSC / VLR, respectively. UMTS supports encryption of the radio
interface and the integrity protection of signalling messages.

UMTS – WCDMA Technology

The first Multiple Access Third Generation Partnership Project (3GPP)

Wideband Code Division networks (WCDMA) were launched in 2002. At the end of
2005, there were 100 WCDMA networks open and a total of more than 150
operators with licenses for frequencies WCDMA operation. Currently, WCDMA
networks are deployed in UMTS band of around 2 GHz in Europe and Asia, including
Japan and America Korea. WCDMA is deployed in the 850 and 1900 of the existing
frequency allocations and the new 3G band 1700/2100 should be available in the
near future. 3GPP has defined WCDMA operation for several additional bands, which
are expected to be commissioned in the coming years.

As WCDMA mobile penetration increases, it allows WCDMA networks to carry

a greater share of voice and data traffic. WCDMA technology provides some
advantages for the operator in that it allows the data, but also improves the voice of
base. Voice capacity offered is very high due to interference control mechanisms,
including frequency reuse of 1, fast power control, and soft handover.

WCDMA can offer a lot more voice minutes to customers. Meanwhile WCDMA
can also improve broadband voice service with AMR codec, which clearly provides
better voice quality than fixed telephone landline. In short, WCDMA can offer more
voice minutes with better quality.

In addition to the high spectral efficiency, third-generation (3G) WCDMA provides

even more dramatic change in capacity of the base station and the efficiency of the
equipment. The high level of integration in the WCDMA is achieved due to the
broadband carrier: a large number of users supported by the carrier, and less radio
frequency (RF) carriers are required to provide the same capacity.

With less RF parts and more digital baseband processing, WCDMA can take
advantage of the rapid evolution of digital signal processing capability. The level of
integration of the high base station enables efficient building high capacity sites since
the complexity of RF combiners, additional antennas or power cables can be avoided.
WCDMA operators are able to provide useful data services, including navigation,
person to person video calls, sports and video and new mobile TV clips.

WCDMA enables simultaneous voice and data which allows, for example,
browsing or email when voice conferencing or video sharing in real time during voice
calls.

The operators also offer mobile connectivity to the Internet and corporate intranet
with maximum bit rate of 384 kbps downlink and both uplink. The first terminals and
networks have been limited to 64 to 128 kbps uplink while the latter products
provide 384 kbps uplink.

WCDMA-3G

3G wireless service has been designed to provide high data speeds, always-on
data access, and greater voice capacity. Listed below are a few notable points: The
high data speeds, measured in Mbps, enable full motion video, high-speed internet
access and video-conferencing. 3G technology standards include UMTS, based on
WCDMA technology (quite often the two terms are used interchangeably) and
CDMA2000, which is the outgrowth of the earlier CDMA 2G technology.

UMTS standard is generally preferred by countries that use GSM network.

CDMA2000 has various types, including 1xRTT, 1xEV-DO and 1xEV-DV. The data rates
they offer range from 144 kbps to more than 2 mbps.

Sub-systems of 3G Network

A GSM system is basically designed as a combination of three major subsystems:

 Network Subsystem (NSS): MSC/VLR, HLR, AuC, SMSC, EIR, MGW. Common for
both 2G & 3G Network.

 UTRAN: RNC & RBS.

 Operation and maintenance Support Subsystem (OSS).

There are three dominant interfaces, namely,

 IuCS: Between RNC and MSC for speech & Circuit data;

 IuPS: Between RNC & SGSN for packet data;

 Uu interface: Between the RNC and MS.

UMTS – 3GPP

3rd Generation Partnership Project or 3GPP, is the standardization group for

mobile networks and is in existence since 1998. 3GPP specification come in bundles
called

―Release‖.

3rd Generation Partnership Project (3GPP)

3GPP releases are from Release 99 to Release 7.

 3GPP2 is the corresponding part of 3GPP market. 3GPP2 standards body has
also developed a large set of specifications describing own mobile network
technology, the current generation being labelled as CDMA2000 ©. 3GPP2 is 3GPP
concepts and solutions, but is chosen selectively different. Regarding LTE, there has
been a growing interest of 3GPP2 operators in recent years to allow between flexible
and efficient. The inheritance 3GPP2 technology includes a component called 1xRTT
CS and PS component (EVDO vs eHRPD). 3GPP2 consider their (eHRPD) high-speed
packet data network as equivalent to 3GPP old system, the right to transfer
procedures optimized specially designed.

Architecture of the 3GPP System

The overall architecture of the 3GPP, evolved system as well as the core and
access networks already existing 3GPP defined are called "legacy 3GPP system".

The access networks which are not defined by the 3GPP, but may be used in
conjunction with the evolved 3GPP system are called "non-3GPP access networks".
 The area of service must be understood as the multitude of IP services, so in
general they are represented and implemented by packet data networks (PDN). IP
service can simply offer a raw IP connectivity (i.e. allowing an internet connection),
providing a connection to a corporate network, or an advanced IP-based control
functionality such as telephony and instant messaging via IMS.

It is called "Evolved UTRAN" (EUTRAN). GERAN and UTRAN are the

existing radio access networks and are connected to the legacy PS domain. Evolved
Packet Core (EPC) in addition to the basic functions to manage packet routing and
forwarding (for the transport of user data) contains all the features necessary to
control especially for mobility, session handling, safety and load.

For interworking with legacy CS domain, the CS core network should be

considered as well and interfaced with the backend IMS. The dotted arrow indicates
an optional interconnection between legacy CS core networks and the new network
Evolved Packet Core, the decline in profit to the CS domain for voice services, if
necessary.

UMTS – Radio Access Network

The more general term "Evolved Radio Access Network" (eRAN), can also be used as
part of signalling protocols, as the term "access stratum" (AS) can be used. The
comparison reveals that E-UTRAN consists of one type of nodes, namely Evolved
Node B (eNodeB), and the variety of interconnections is reduced to a minimum.
eNodeB is a radio base station and transmits/receives via its antenna in an area (cell),
limited by physical factors (signal strength, interference conditions, and conditions of
radio wave propagation). It has logical interfaces X2 with neighbouring eNodeB and
the EPC via S1.

Both have a control part (that is, say for signalling) and a user plane part (for
payload data). Point to the EU reference (which includes radio link interface and a
mobile network protocol stack bound) is called "LTE-U u" to indicate that it differs
from the legacy counterpart EU X2 connectivity neighbouring eNodeBs. They may be
considered for most of the E-UTRAN and is used in most cases of handovers between
radio cells.

As the UE moves, long handover preparation is done via signalling, through X2

between the two data eNodeBs and affected users can be transmitted between them
for a short period of time. Only in special cases, it may happen that X2 is not
configured for eNodeB between two neighbours. In this case transfers are always
supported, but the preparation of transfer and the data transmission is then made
via the EPC. Accordingly, higher latency and less "homogeneity" must therefore be
provided.

In more detail, the functions performed by the eNodeB are:

 Radio Resource Management: Radio Bearer Control, Radio Admission Control,

Connection Control Mobility, dynamic allocation of resources (i.e. scheduling)
to UES as uplink and downlink.

 Header compression of IP and encryption of user data stream.

 Forwarding the data packets of user plane to the EPC (especially, toward the
GW node service).

 Transport level packet marking in the uplink, for example, DiffServ code point
setting, based on the QoS class index (QCI) of the EPS bearer associated.

 Planning and delivery of paging messages (on request of MS).

 Planning and transmission of broadcast information (origin of the MME or O &
M).

 Measurement configuration delivering and reporting on the extent of mobility
and programming.
UMTS – evolved packet core

By the early architectural work for the system evolved 3GPP, two views on the
implementation of mobility with the user plane and control plane protocols were
presented. The first was promoted as the good performance of the GPRS Tunnelling
Protocol (GTP), while the other pushed for the new (and the so-called "base" of the
IETF) protocols.

Both had good arguments on their side:

 GTP evolution : This protocol has proven its usefulness and capabilities to
operators, and was very successful in the large scale operations. It was
designed exactly to the needs of the mobile networks PS.

 IETF based protocols : IETF is the de facto standards body for the internet.
Their mobility protocols have evolved from focusing on mobile IP-based
network client to "Proxy Mobile IP (MIP)." PMIP was standardized in 3GPP
Evolved parallel system. (But Mobile IP client base is used in EPS in conjunction
with non-3GPP access support.)

EPC for 3GPP access in non-roaming

The functions provided by the reference points and the protocols employed are:

LTE-Uu

LTE-Uu is the point of reference for radio interface between EU and eNodeB,
encompasses control plane and user plane. The top layer of the control plan is called
" Radio Resource Control" (RRC). It is stacked on "Packet Data Convergence
Protocol" (PDCP), Radio Link Control and MAC layers.
S1-U

SI-U is the point for user plane traffic between eNodeB and serve GW
reference. The main activity via this benchmark is to transfer IP packets encapsulated
users arising from traffic or tunnel shape. Encapsulation is needed to realize the
virtual IP link between eNodeB and GW service, even during the movement of EU,
and thus enable mobility. The protocol used is based on GTP-U.

S1-MME

S1-MME is the point for the control plane between eNodeB and MME
reference. All control activities are carried out on it, for example, signalling for
attachment, detachment, and the establishment of the support of the change, safety
procedures, etc. Note that some of this traffic is transparent to the E-UTRAN and is
exchanged directly between EU and MS, it is a part called "non-access stratum" (NAS)
signalling.

S5

S5 is the benchmark that includes the control and user plane between GW and PDN
GW Service and applies only if both nodes reside in the HPLMN; the corresponding
reference point when serving GW is VPLMN is called S8. As explained above, two
protocol variants are possible here, an enhanced GPRS Tunnelling Protocol (GTP) and
Proxy Mobile IP (PMIP).
S6a

S6a is the reference point for the exchange of information relating to

subscriptions equipment (download and purging). It corresponds to Gr and D
reference point in the existing system, and is based on the DIAMETER protocol.

SGi
 This is the point of exit for DPR, and corresponds to the Gi reference point
GPRS and Wi in I-WLAN. IETF protocols are based here for the user plane (i.e. IPv4
and IPv6 packet forwarding) protocols and control plane as DHCP and
radius/diameter for configuring IP address/external network protocol are used.

S10

S10 is a reference point for the MME relocation purposes. It is a pure control
plane interface and advanced GTP-C protocol is used for this purpose.

S11

S11 is a reference point for the existing control plane between MME and GW
service. It employs the advanced GTP-C (GTP-C v2) protocol. The holder(s) of data
between eNodeB and serve GW are controlled by the concatenation S1-S11 and
MME.

S13

S13 is the reference point for Equipment Identity Register (EIR) and MME, and
it is used for identity control (e.g. based on IMEI, if blacklisted). It uses the diameter
protocol SCTP.

Gx

Gx is the reference point of the QoS policy filtering policy and control the load
between PCRF and PDN GW. It is used to provide filters and pricing rules. The
protocol used is the DIAMETER.

Gxc
 Gxc is the reference point that exists in over Gx but is located between GW and
PCRF and serves only if PMIP is used on S5 or S8.

Rx

Rx is defined as an application function (AF), located in NDS and PCRF for the
exchange of policy and billing information; it uses the DIAMETER protocol.

EPC for 3GPP Access in Roaming

In roaming this case the user plane either:

Extends back to the HPLMN (via an interconnection network), which means that all
EU user traffic is routed through a PDN GW in the HPLMN, where the DPRs are
connected;
or For the sake of a more optimal way of traffic, it leaves a PDN GW in the VPLMN to
a local PDN.

The first is called "home routed traffic" and the second is called "local
breakout". (Note that the second term is also used in the discussion of traffic
optimization for home NBs/eNodeB, but with a different meaning because in the
concept of roaming 3GPP, the control plan always involves the HPLMN).

Interworking between EPC and Legacy

From the beginning, it was clear that the 3GPP Evolved system will
interoperate seamlessly with existing 2G and 3G systems, 3GPP PS widely deployed
or, more precisely, with GERAN and UTRAN GPRS base (For aspects of interworking
with the old CS system for the treatment of optimized voice).

The question of the basic architectural design to 2G/3G in EPS is the location of
the GGSN map. Two versions are available, and both are supported:
  The GW used : It is the normal case where serving the GW ends the user plane
(as seen in the existing GPRS network).The control plan is completed in the
MME, according to the distribution of users and control plane in EPC. S3 and S4
reference points are introduced, and they are based on GTP-U and GTP-C,
correspondingly. S5/S8 is chained to the PDN GW. The advantage is that
interoperability is smooth and optimized. The downside is that for this kind of
interoperability SGSN must be upgraded to Rel. 8 (due to the necessary
support new features on S3 and S4).

 The PDN GW : In this case the unchanged benchmark inheritance Gn (when
roaming, it would Gp) is reused between SGSN and PDN GW, for both control
and user plane. The advantage of this use is that SGSN can be pre-Rel. 8.
Furthermore, it carries a certain restriction on IP versions, transfer and S5 / S8
protocol.

Interworking with Legacy 3GPP CS System

During the 3GPP Evolved design phase, it became clear that the legacy CS
system, with its most important service "voice" communication, could not be
ignored by the new system. The operators were simply too related investments in the
field, and so very efficient interworking was requested.

Two solutions have been developed:

Single Radio Voice Call Continuity (SRVCC) for transferring voice calls from LTE (with
voice over IMS) to the legacy system.
 CS fallback: Enabling a temporary move to the legacy CS before a CS incoming
or outgoing activity is performed.

Single Radio Voice Call Continuity (SRVCC)

 In this solution chosen by 3GPP for SRVCC with GERAN/UTRAN, a specially
reinforced MSC is connected via a new interface control plane for MME. Note that
the MSC serving the EU can be different than supporting the Sv interface. In the IMS,
an application server (AS) for SRVCC is necessary. Sv is based on GTPv2 and helps
prepare resources in the target system (access and core network and the
interconnection between CS and IMS domain), while being connected to access the
source.

Similarly, with SRVCC CDMA 1xRTT requires interworking 1xRTT Server (IWS),
which supports the interface and signal relay from / to 1xRTT MSC serving the UE
S102 with the same purpose. S102 is a tunnel interface and transmits 1xRTT signaling
messages; between MME and UE these are encapsulated.

CS Fallback

Serving GW and PDN GW are not separated (S5/S8 is not exposed) and the VLR
is integrated with the MSC server. A new SG interface is introduced between the MSC
Server/VLR and MME, allowing combined and coordinated procedures. The concept
consists of:

 Signal relay to end the CS request (incoming calls, handling network triggered
additional service or SMS Legacy) from the MSC Server for MS on SG and vice
versa;

 The combined operating procedures between the PS domain and the CS
domain.

Interworking with Non-3GPP Access

Interworking with different system of 3GPP access networks (called non-

3GPP/access) was an important target for SAE; this should be done under the EPC
umbrella. This interoperability can be achieved at different levels (and in fact, this
was done on the layer 4 with VCC/SRVCC). But for the generic type of interworking, it
seemed necessary to rely on generic mechanisms, so the IP level seemed most
appropriate.

In general, complete systems for mobile and fixed networks have an architecture
similar to that described above. For the evolved 3GPP system there is normally an
access network and a core network. In the interworking architecture scheduled
evolved 3GPP system, other access technologies systems connect to the EPC.
In general, complete mobile network system and fixed network systems have a
similar architecture as described outlined in Evolved 3GPP system and normally
consist of an access network and a core network/ It was also decided to allow two
different types of interoperability, based on the property of the access systems. For
networks with non-3GPP access confidence, it is assumed that secure communication
between them and the EPC is implemented and also robust data protection is
sufficiently guaranteed.

UMTS – GPRS Tunnelling Protocol

The generation of GPRS Tunnelling Protocol (GTP) was virtually impossible, but
is also not desirable to give it for the new system, but, on the other hand, it is quite
understandable that the improvements are also needed in order to be able to
interact with the world of legacy PS smoothly and support functions needed for the
newest system.

GPRS Tunnelling Protocol (GTP)

GTP protocol is designed for tunnelling and encapsulation of data units and
control messages in GPRS. Since its design in the late 1990s, it was put to deploy on a
large scale, and solid experience has been gathered. GTP for Evolved 3GPP system is
available in two variants, control and user plane. GTP-C manages the control plane
signalling, and it is necessary in addition to the data transfer protocol on the purity of
the user, GTP-U; it is called user plane. Current versions, suitable for EPS are GTPv1
US and GTPv2-C.
 The peculiarity of GTP is that it supports the separation of traffic within its
primary GTP tunnel holder, or in other words, the ability to group them together and
treat carriers. The ends of GTP tunnels are identified by TEIDs (Tunnel Endpoint
identifiers); they are assigned to the local level for the uplink and downlink by peer
entities and reported transversely between them. TEIDs are used on different
granularity by specific example PDN connection on S5 and S8 and EU on S3 / S4 /
S10 / S11 interfaces.

Control Plane of GPRS Tunnelling Protocol

GTPv2-C is used on the EPC signalling interfaces (including SGSNs of at least Rel. 8).
For

example:

 S3 (between SGSN and MME),


 S4 (between SGSN and Serving GW),

 S5 and S8 (between Serving GW and PDN GW),

 S10 (between two MMEs), and

 S11 (between MME and Serving GW).

 Corresponding to this, a typical GTPv2-C protocol data unit like shown in the
figure above, the specific part GTP is preceded by IP and UDP headers, it consists of
a header GTPv2-C and part containing information GTPv2-C variable in number,
length and format, depending on the type of the message. As the echo and the
notification of a protocol version is not supported, TEID information is not present.
The version is obviously firmly set at 2 in this version of the protocol.

GTP had a complex legacy extension header mechanism; it is not used in most
GTPv2-C. The message type is defined in the second byte (so the maximum of 256
messages can be defined for future extensions). Below table provides an overview
of messages currently defined GTPv2-C. The length of the message is coded in bytes
3 and 4 (measured in bytes and not containing the first four bytes themselves).

TEID is the ID of the tunnel end point, a single value on the opposite/receiving
side; it allows multiplexing and de-multiplexing tunnels at one end in the very
frequent cases over a GTP tunnel must be distinguished.
Enhanced GTPv1-U

Only a small but effective improvement was applied to GTP-U, and for that it
was not considered necessary to strengthen the number of protocol version. Thus,
we still expect GTPv1-U, but at least it‘s most recent Rel. 8.

The protocol stack is essentially the same as for GTPv2-C with only the name of the
layers and the protocols substituted accordingly. The extension header mechanism
is kept in place; it allows inserting two elements if necessary.

 UDP source port of the triggering message (two octets);


 PDCP PDU number: related to the characteristic transfer without loss; in this
case, data packets need to be numbered in the EPC (two octets).

The improvement is the ability to transmit an "end market" in the user plane. It is
used in the inter-eNodeB handover procedure and gives the indication that the
pathway is activated immediately after the data packet, for example, the feature is
not necessary to pre-Rel.8 because GTP-U did not end in the radio access node (i.e.
not in the BS or NodeB) only a few messages exist. GTPv1-U, and they are listed in
the table above.

It is clear that, in fact a very limited kind of signaling is possible via GTPv1-U
(echo mechanisms and end labeling). The only message that the transfer of real user
data is of type 255, the so-called G-PDU message; the only piece of information it
carries, after the header is the original data packet from a user or external PDN
equipment.

Not all instances of GTP-U tunnels are listed in the reference architecture (which
aimed to capture the associations were no longer living between network nodes);
temporary tunnels are possible:

 Between two Serving GWs, applicable for the transfer based on S1, in the case
that the service is moved GW;

 Between two SGSNs, corresponds to the previous case, but in the legacy PS
network;

 Between two RNCs, applicable for the relocation of the RNC in the 3G PS
network (no relation to the EPC, it is mentioned here just for completeness).
 UNIT - IV

ADHOC BASIC CONCEPTS

A wireless ad hoc network (WANET) is a decentralized type of wireless

network. The network is ad hoc because it does not rely on a pre existing
infrastructure, such as routers in wired networks or access points in managed
(infrastructure) wireless networks. Instead, each node participates in routing by
forwarding data for other nodes, so the determination of which nodes forward data is
made dynamically on the basis of network connectivity.

In addition to the classic routing, ad hoc networks can use flooding for
forwarding data. Wireless mobile ad hoc networks are self-configuring, dynamic
networks in which nodes are free to move. Wireless networks lack the complexities of
infrastructure setup and administration, enabling devices to create and join networks
"on the fly" - anywhere, anytime.

A wireless ad-hoc network, also known as IBSS - Independent Basic Service

Set, is a computer network in which the communication links are wireless. The
network is ad-hoc because each node is willing to forward data for other nodes, and so
the determination of which nodes forward data is made dynamically based on the
network connectivity. This is in contrast to older network technologies in which some
designated nodes, usually with custom hardware and variously known as routers,
switches, hubs, and firewalls, perform the task of forwarding the data.

Minimal configuration and quick deployment make ad hoc networks suitable for
emergency situations like natural or human-induced disasters, military conflicts. The
earliest wireless ad-hoc networks were called "packet radio" networks, and were
sponsored by Defense Advanced Research Projects Agency (DARPA) in the early
1970s. Bolt, Beranek and Newman Technologies (BBN) and SRI International
designed, built, and experimented with these earliest systems.
Experimenters included Jerry Burchfield, Robert Kahn, and Ray Tomlinson of
later TEN-EXtended (TENEX), Internet and email fame. Similar experiments took
place in the Ham radio community. It is interesting to note that these early packet
radio systems predated the Internet, and indeed were part of the motivation of the
original Internet Protocol suite. Later DARPA experiments included the Survivable
Radio Network (SURAN) project, which took place in the 1980s.

Another third wave of academic activity started in the mid-1990s with the
advent of inexpensive 802.11 radio cards for personal computers. Current wireless ad-
hoc networks are designed primarily for military utility.

CHARACTERISTICS

MANET

It is an infrastructureless IP based network of mobile and wireless machine

nodes connected with radio. In operation, the nodes of a MANET do not have a
centralized administration mechanism. It is known for its routeable network
properties where each node act as a ―router‖ to forward the traffic to other
specified node in the network.
 The characteristics are:

 In MANET, each node act as both host and router. That is it is autonomous in
behaviour.

 Multi-hop radio relaying- When a source node and destination node for a message
is out of the radio range, the MANETs are capable of multi-hop routing.

 Distributed nature of operation for security, routing and host configuration. A
centralized firewall is absent here.

 The nodes can join or leave the network anytime, making the network topology
dynamic in nature.

 Mobile nodes are characterized with less memory, power and light weight
features.

 The reliability, efficiency, stability and capacity of wireless links are often inferior
when compared with wired links. This shows the fluctuating link bandwidth of
wireless links.

 Mobile and spontaneous behaviour which demands minimum human intervention
to configure the network.

 All nodes have identical features with similar responsibilities and capabilities and
hence it forms a completely symmetric environment.

 High user density and large level of user mobility.

 Nodal connectivity is intermittent.

 Distributed operation: There is no background network for the central control of
the network operations, the control of the network is distributed among the
nodes. The nodes involved in a MANET should cooperate with each other and
communicate among themselves and each node acts as a relay as needed, to
implement specific functions such as routing and security.

 Multi hop routing: When a node tries to send information to other nodes which is
out of its communication range, the packet should be forwarded via one or more
intermediate nodes.

 Autonomous terminal: In MANET, each mobile node is an independent node,
which could function as both a host and a router.

 Dynamic topology: Nodes are free to move arbitrarily with different speeds; thus,
the network topology may change randomly and at unpredictable time. The nodes
in the MANET dynamically establish routing among themselves as they travel
around, establishing their own network.

 Light-weight terminals: In maximum cases, the nodes at MANET are mobile with
less CPU capability, low power storage and small memory size.

 Shared Physical Medium: The wireless communication medium is accessible to
any entity with the appropriate equipment and adequate resources. Accordingly,
access to the channel cannot be restricted.

APPLICATIONS

 Military battlefield: Ad-Hoc networking would allow the military to take

advantage of commonplace network technology to maintain an information
network between the soldiers, vehicles, and military information head
quarter.

 Collaborative work: For some business environments, the need for
collaborative computing might be more important outside office
environments than inside and where people do need to have outside
meetings to cooperate and exchange information on a given project.

 Local level: Ad-Hoc networks can autonomously link an instant and temporary
multimedia network using notebook computers to spread and share
information among participants at a e.g. conference or classroom. Another
appropriate local level application might be in home networks where devices
can communicate directly to exchange information.

 Personal area network and bluetooth: A personal area network is a short
range, localized network where nodes are usually associated with a given
person. Short-range MANET such as Bluetooth can simplify the inter
communication between various mobile devices such as a laptop, and a
mobile phone.

Commercial Sector: Ad hoc can be used in emergency/rescue operations for

disaster relief efforts, e.g. in fire, flood, or earthquake. Emergency rescue
operations must take place where non-existing or damaged
communications infrastructure and rapid
 deployment of a communication network is needed.

 Mobile Ad hoc Networks (MANET) : A mobile ad hoc network (MANET) is a

continuously self-configuring, infrastructure-less network of mobile devices
connected without wires.

 Vehicular Ad hoc Networks (VANETs) are used for communication between
vehicles and roadside equipment. Intelligent vehicular ad hoc networks (In
VANETs) are a kind of artificial intelligence that helps vehicles to behave in
intelligent manners during vehicle-to-vehicle collisions, accidents.

 Smart Phone Ad hoc Networks (SPANs) leverage the existing hardware
(primarily Bluetooth and Wi-Fi) in commercially available smart phones to
create peer-to-peer networks without relying on cellular carrier networks,
wireless access points, or traditional network infrastructure.

 Internet based mobile ad hoc networks (iMANETs) are ad hoc networks that
link mobile nodes and fixed Internet-gateway nodes. One implementation of
this is Persistent System's Cloud Relay.

 Military / Tactical MANETs are used by military units with emphasis on
security, range, and integration with existing systems.

DESIGN ISSUES

 The wireless link characteristics are time-varying in nature: There are

transmission impediments like fading, path loss, blockage and interference that
adds to the susceptible behaviour of wireless channels. The reliability of
wireless transmission is resisted by different factors.

 Limited range of wireless transmission – The limited radio band results in
reduced data rates compared to the wireless networks. Hence optimal usage
of bandwidth is necessary by keeping low overhead as possible.
  Packet losses due to errors in transmission – MANETs experience higher packet
loss due to factors such as hidden terminals that results in collisions, wireless
channel issues (high bit error rate (BER)), interference, frequent breakage in
paths caused by mobility of nodes, increased collisions due to the presence of
hidden terminals and uni-directional links.

 Route changes due to mobility- The dynamic nature of network topology
results in frequent path breaks.

 Frequent network partitions- The random movement of nodes often leads to
partition of the network. This mostly affects the intermediate nodes.

 Limited bandwidth: Wireless link continue to have significantly lower capacity
than infra structured networks. In addition, the realized throughput of
wireless communication after accounting for the effect of multiple access,
fading, noise, and interference conditions, etc., is often much less than a
radio‘s maximum transmission rate.

 Dynamic topology: Dynamic topology membership may disturb the trust
relationship among nodes. The trust may also be disturbed if some nodes are
detected as compromised.

 Routing Overhead: In wireless adhoc networks, nodes often change their
location within network. So, some stale routes are generated in the routing
table which leads to unnecessary routing overhead.

 Hidden terminal problem: The hidden terminal problem refers to the collision
of packets at a receiving node due to the simultaneous transmission of those
nodes that are not within the direct transmission range of the sender, but are
within the transmission range of the receiver.

 Packet losses due to transmission errors: Ad hoc wireless networks
experiences a much higher packet loss due to factors such as increased
 collisions due to the presence of hidden terminals, presence of interference,
uni-directional links, frequent path breaks due to mobility of nodes.

 Mobility-induced route changes: The network topology in an ad hoc wireless
network is highly dynamic due to the movement of nodes; hence an on-going
session suffers frequent path breaks. This situation often leads to frequent
route changes.

 Battery constraints: Devices used in these networks have restrictions on the

power source in order to maintain portability, size and weight of the device.

 Security threats: The wireless mobile ad hoc nature of MANETs brings new
security challenges to the network design. As the wireless medium is
vulnerable to eavesdropping and ad hoc network functionality is established
through node cooperation, mobile ad hoc networks are intrinsically exposed
to numerous security attacks.
ROUTING

Routing is the process of selecting best paths in a network. In the past, the term routing
also meant forwarding network traffic among networks. However, that latter function
is better described as forwarding. Routing is performed for many kinds of
networks, including the telephone network (circuit switching), electronic data
networks (such as the Internet), and transportation networks. This article is concerned
primarily with routing in electronic data networks using packet switching technology.

In packet switching networks, routing directs packet forwarding (the transit of

logically addressed network packets from their source toward their ultimate
destination) through intermediate nodes. Intermediate nodes are typically network
hardware devices such as routers, bridges, gateways, firewalls, or switches. General-
purpose computers can also forward packets and perform routing, though they are not
specialized hardware and may suffer from limited performance.

The routing process usually directs forwarding on the basis of routing tables, which
maintain a record of the routes to various network destinations. Thus, constructing
routing tables, which are held in the router's memory, is very important for efficient
 routing. Most routing algorithms use only one network path at a time. Multipath
routing techniques enable the use of multiple alternative paths.

In internetworking, the process of moving a packet of data from source to

destination. Routing is usually performed by a dedicated device called a router.
Routing is a key feature of the Internet because it enables messages to pass from one
computer to another and eventually reach the target machine. Each intermediary
computer performs routing by passing along the message to the next computer. Part
of this process involves analyzing a routing table to determine the best path.

Routing is often confused with bridging, which performs a similar function. The
principal difference between the two is that bridging occurs at a lower level and is
therefore more of a hardware function whereas routing occurs at a higher level where
the software component is more important. And because routing occurs at a higher
level, it can perform more complex analysis to determine the optimal path for the
packet.

ESSENTIAL OF TRADITIONAL ROUTING PROTOCOLS

Link State Routing Protocol

Link state routing has a different philosophy from that of distance vector routing. In
link state routing, if each node in the domain has the entire topology of the domain
the list of nodes and links, how they are connected including the type, cost (metric),
and condition of the links (up or down)-the node can use Dijkstra's algorithm to build
a routing table.
 Concept of link state routing

The figure shows a simple domain with five nodes. Each node uses the same
topology to create a routing table, but the routing table for each node is unique
because the calculations are based on different interpretations of the topology. This
is analogous to a city map. While each person may have the same map, each needs to
take a different route to reach her specific destination.

The topology must be dynamic, representing the latest state of each node
and each link. If there are changes in any point in the network (a link is down, for
example), the topology must be updated for each node.

Building Routing Tables

In link state routing, four sets of actions are required to ensure that each
node has the routing table showing the least-cost node to every other node.

1. Creation of the states of the links by each node, called the link state packet (LSP).

2. Dissemination of LSPs to every other router, called flooding, in an efficient and

reliable way.
3. Formation of a shortest path tree for each node.

4. Calculation of a routing table based on the shortest path tree.

Creation of Link State Packet (LSP)

A link state packet can carry a large amount of information. For the moment,
however, we assume that it carries a minimum amount of data: the node identity,
the list of links, a sequence number, and age. The first two, node identity and the list
of links, are needed to make the topology. The third, sequence number, facilitates
flooding and distinguishes new LSPs from old ones. The fourth, age, prevents old LSPs
from remaining in the domain for a long time. LSPs are generated on two occasions:

1. When there is a change in the topology of the domain. Triggering of LSP

dissemination is the main way of quickly informing any node in the domain to update
its topology.

2. On a periodic basis. The period in this case is much longer compared to distance
vector routing. As a matter of fact, there is no actual need for this type of LSP
dissemination.

It is done to ensure that old information is removed from the domain. The
timer set for periodic dissemination is normally in the range of 60 min or 2 h based
on the implementation. A longer period ensures that flooding does not create too
much traffic on the network.

Flooding of LSPs After a node has prepared an LSP, it must be disseminated to

all other nodes, not only to its neighbours. The process is called flooding and based
on the following:

1. The creating node sends a copy of the LSP out of each interface.
2. A node that receives an LSP compares it with the copy it may already have. If the
newly arrived LSP is older than the one it has (found by checking the sequence
number), it discards the LSP. If it is newer, the node does the following:

a. It discards the old LSP and keeps the new one.

b. It sends a copy of it out of each interface except the one from which the packet
arrived. This guarantees that flooding stops somewhere in the domain (where a node
has only one interface).

Formation of Shortest Path Tree

Dijkstra Algorithm After receiving all LSPs, each node will have a copy of the
whole topology. However, the topology is not sufficient to find the shortest path to
every other node; a shortest path tree is needed.

A tree is a graph of nodes and links; one node is called the root. All other
nodes can be reached from the root through only one single route. A shortest path
tree is a tree in which the path between the root and every other node is the
shortest. What we need for each node is a shortest path tree with that node as the
root.

The Dijkstra algorithm creates a shortest path tree from a graph. The algorithm
divides the nodes into two sets: tentative and permanent. It finds the neighbours of a
current node, makes them tentative, examines them, and if they pass the criteria,
makes them permanent. The following shows the steps. At the end of each step, we
show the permanent (filled circles) and the tentative (open circles) nodes and lists
with the cumulative costs.
OSPF

The Open Shortest Path First or OSPF protocol is an intra

domain routing protocol based on link state routing. Its domain is also an
autonomous system. Areas To handle routing efficiently and in a timely manner,
OSPF divides an autonomous system into areas. An area is a collection of networks,
hosts, and routers all contained within an autonomous system. An autonomous
system can be divided into many different areas.

All networks inside an area must be connected. Routers inside an area flood
the area with routing information. At the border of an area, special routers called
area border routers summarize the information about the area and send it to other
areas. Among the areas inside an autonomous system is a special area called the
backbone; all the areas inside an autonomous system must be connected to the
backbone. In other words, the backbone serves as a primary area and the other areas
as secondary areas.

This does not mean that the routers within areas cannot be connected to each other,
however. The routers inside the backbone are called the backbone routers. Note that
a backbone router can also be an area border router. If, because of some problem,
the connectivity between a backbone and an area is broken, a virtual link between
routers must be created by an administrator to allow continuity of the functions of
the backbone as the primary area.Each area has an area identification. The area
identification of the backbone is zero. Below Figure shows an autonomous system
and its areas.

Areas in an autonomous system

Metric

The OSPF protocol allows the administrator to assign a cost, called the metric, to
each route. The metric can be based on a type of service (minimum delay, maximum
throughput, and so on). As a matter of fact, a router can have multiple routing tables,
each based on a different type of service. Types of Links In OSPF terminology, a
connection is called a link. Four types of links have been defined: point-to-point,
transient, stub, and virtual.

Types of links
A point-to-point link connects two routers without any other host or router in
between. In other words, the purpose of the link (network) is just to connect the two
routers. An example of this type of link is two routers connected by a telephone line
or a T line. There is no need to assign a network address to this type of link.
Graphically, the routers are represented by nodes, and the link is represented by a
bidirectional edge connecting the nodes. The metrics, which are usually the same, are
shown at the two ends, one for each direction.

Point-to-point link

A transient link is a network with several routers attached to it. The data can
enter through any of the routers and leave through any router. All LANs and some
WANs with two or more routers are of this type. In this case, each router has many
neighbors. For example, consider the Ethernet in Figure. Router A has routers B, C, D,
and E as neighbors. Router B has routers A, C, D, and E as neighbors.

Transient link

A stub link is a network that is connected to only one router. The data
packets enter the network through this single router and leave the network through
this same router. This is a special case of the transient network. We can show this
situation using the router as a node and using the designated router for the network.
When the link between two routers is broken, the administration may create
a virtual link between them, using a longer path that probably goes through several
routers. Graphical Representation Let us now examine how an AS can be
represented graphically. Figure shows a small AS with seven networks and six routers.
Two of the networks are point-to-point networks. We use symbols such as Nl and N2
for transient and stub networks. There is no need to assign an identity to a point-to-
point network. The figure also shows the graphical representation of the AS as seen
by OSPF.
 Distance Vector Routing Protocol

Routing Information Protocol (RIP) is an implementation of the distance

vector protocol. Open Shortest Path First (OSPF) is an implementation of the link
state protocol.

Border Gateway Protocol (BGP) is an implementation of the path vector protocol.

In distance vector routing, the least-cost route between any two nodes is
the route with minimum distance. In this protocol, as the name implies, each node
maintains a vector (table) of minimum distances to every node. The table at each
node also guides the packets to the desired node by showing the next stop in the
route (next-hop routing).
Distance vector routing tables

Initialization

The table for node A shows how we can reach any node from this node. For
example, our least cost to reach node E is 6. The route passes through C. Each node
knows how to reach any other node and the cost. Each node can know only the
distance between itself and its immediate neighbors, those directly connected to it.

So for the moment, we assume that each node can send a message to the immediate
neighbors and find the distance between itself and these neighbors.
Sharing - In distance vector routing, each node shares its routing table with its
immediate neighbors periodically and when there is a change.

Updating - When a node receives a two-column table from a neighbor, it needs to

update its routing table.

Updating takes three steps:

1. The receiving node needs to add the cost between itself and the sending node to
each value in the second column. The logic is clear. If node C claims that its distance
to a destination is x mi, and the distance between A and C is y mi, then the distance
between A and that destination, via C, is x + y mi.

2. The receiving node needs to add the name of the sending node to each row as the
third column if the receiving node uses information from any row. The sending node
is the next node in the route.
3. The receiving node needs to compare each row of its old table with the
corresponding row of the modified version of the received table.

a. If the next-node entry is different, the receiving node chooses the row with the
smaller cost. If there is a tie, the old one is kept.

b. If the next-node entry is the same, the receiving node chooses the new row. For
example, suppose node C has previously advertised a route to node X with distance
3. Suppose that now there is no path between C and X; node C now advertises this
route with a distance of infinity Node A must not ignore this value even though its old
entry is smaller. The old route does not exist any more. The new route has a distance
of infinity.

Each node can update its table by using the tables received from other nodes. When
to Share:

Periodic Update A node sends its routing table, normally every 30 s, in a periodic
update. The period depends on the protocol that is using distance vector routing.

Triggered Update A node sends its two-column routing table to its neighbors anytime
there is a change in its routing table. This is called a triggered update.
The change can result from the following.

1. A node receives a table from a neighbor, resulting in changes in its own table after
updating.

2. A node detects some failure in the neighboring links which results in a distance
change to infinity.

RIP

The Routing Information Protocol (RIP) is an intra-domain routing protocol

used inside an autonomous system. It is a very simple protocol based on distance
vector routing. RIP implements distance vector routing directly with some
considerations:

1. In an autonomous system, we are dealing with routers and networks (links). The
routers have routing tables; networks do not.

2. The destination in a routing table is a network, which means the first column
defines a network address.

3. The metric used by RIP is very simple; the distance is defined as the number of
links (networks) to reach the destination. For this reason, the metric in RIP is called a
hop count.

4. Infinity is defined as 16, which means that any route in an autonomous system
using RIP cannot have more than 15 hops.

5. The next-node column defines the address of the router to which the packet is to
be sent to reach its destination.

POPULAR ROUTING PROTOCOLS

i.Destination Sequenced Distance Vector Routing (DSDV)

Destination sequenced distance vector routing (DSDV) is adapted from the

conventional Routing Information Protocol (RIP) to ad hoc networks routing. It adds a
new attribute, sequence number, to each route table entry of the conventional RIP.
Using the newly added sequence number, the mobile nodes can distinguish stale
route information from the new and thus prevent the formation of routing loops.

Packet Routing and Routing Table Management

In DSDV, each mobile node of an ad hoc network maintains a routing table,

which lists all available destinations, the metric and next hop to each destination and
a sequence number generated by the destination node. Using such routing table
stored in each mobile node, the packets are transmitted between the nodes of an ad
hoc network. Each node of the ad hoc network updates the routing table with
advertisement periodically or when significant new information is available to
maintain the consistency of the routing table with the dynamically changing topology
of the ad hoc network.

Periodically or immediately when network topology changes are detected,

each mobile node advertises routing information using broadcasting or multicasting a
routing table update packet. The update packet starts out with a metric of one to
direct connected nodes. This indicates that each receiving neighbor is one metric
(hop) away from the node. It is different from that of the conventional routing
algorithms.

After receiving the update packet, the neighbors update their routing table with
incrementing the metric by one and retransmit the update packet to the
corresponding neighbors of each of them. The process will be repeated until all the
nodes in the ad hoc network have received a copy of the update packet with a
corresponding metric. The update data is also kept for a while to wait for the arrival
of the best route for each particular destination node in each node before updating
its routing table and retransmitting the update packet.
 If a node receives multiple update packets for a same destination during the
waiting time period, the routes with more recent sequence numbers are always
preferred as the basis for packet forwarding decisions, but the routing information is
not necessarily advertised immediately, if only the sequence numbers have been
changed. If the update packets have the same sequence number with the same node,
the update packet with the smallest metric will be used and the existing route will be
discarded or stored as a less preferable route. In this case, the update packet will be
propagated with the sequence number to all mobile nodes in the ad hoc network.

The advertisement of routes that are about to change may be delayed until the
best routes have been found. Delaying the advertisement of possibly unstable route
can damp the fluctuations of the routing table and reduce the number of
rebroadcasts of possible route entries that arrive with the same sequence number.
The elements in the routing table of each mobile node change dynamically to keep
consistency with dynamically changing topology of an ad hoc network.

To reach this consistency, the routing information advertisement must be

frequent or quick enough to ensure that each mobile node can almost always locate
all the other mobile nodes in the dynamic ad hoc network. Upon the updated routing
information, each node has to relay data packet to other nodes upon request in the
dynamically created ad hoc network.

ii.Dynamic Source Routing Protocol (DSR)

Dynamic Source Routing (DSR) is a routing protocol for wireless mesh

networks. It is similar to AODV in that it forms a route on-demand when a
transmitting node requests one. However, it uses source routing instead of relying on
the routing table at each intermediate device.

Determining source routes requires accumulating the address of each device

between the source and destination during route discovery. The accumulated path
information iscached by nodes processing the route discovery packets. The learned
paths are used to route packets. To accomplish source routing, the routed packets
contain the address of each device the packet will traverse. This may result in high
overhead for long paths or large addresses, like IPv6.
 To avoid using source routing, DSR optionally defines a flow id option that
allows packets to be forwarded on a hop-by-hop basis. This protocol is truly based on
source routing whereby all the routing information is maintained (continually
updated) at mobile nodes. It has only two major phases, which are Route Discovery
and Route Maintenance. Route Reply would only be generated if the message has
reached the intended destination node (route record which is initially contained in
Route Request would be inserted into the Route Reply).
To return the Route Reply, the destination node must have a route to the
source node. If the route is in the Destination Node's route cache, the route would be
used. Otherwise, the node will reverse the route based on the route record in the
Route Request message header (this requires that all links are symmetric). In the
event of fatal transmission, the Route Maintenance Phase is initiated whereby the
Route Error packets are generated at a node.

The erroneous hop will be removed from the node's route cache; all routes
containing the hop are truncated at that point. Again, the Route Discovery Phase is
initiated to determine the most viable route.

Dynamic source routing protocol (DSR) is an on-demand protocol designed to

restrict the bandwidth consumed by control packets in ad hoc wireless networks by
eliminating the periodic table-update messages required in the table-driven
approach. The major difference between this and the other on-demand routing
protocols is that it is beacon-less and hence does not require periodic hello packet
(beacon) transmissions, which are used by a node to inform its neighbors of its
presence.

The basic approach of this protocol (and all other on-demand routing
protocols) during the route construction phase is to establish a route by flooding
RouteRequest packets in the network. The destination node, on receiving a
RouteRequest packet, responds by sending a RouteReply packet back to the source,
which carries the route traversed by the RouteRequest packet received.

Consider a source node that does not have a route to the destination. When it
has data packets to be sent to that destination, it initiates a RouteRequest packet.
This RouteRequest is flooded throughout the network. Each node, upon receiving a
RouteRequest packet, rebroadcasts the packet to its neighbors if it has not forwarded
it already, provided that the node is not the destination node and that the packet‘s
time to live (TTL) counter has not been exceeded.

Each RouteRequest carries a sequence number generated by the source node

and the path it has traversed. A node, upon receiving a RouteRequest packet, checks
the sequence number on the packet before forwarding it. The packet is forwarded
only if it is not a duplicate RouteRequest. The sequence number on the packet is used
to prevent loop formations and to avoid multiple transmissions of the same
RouteRequest by an intermediate node that receives it through multiple paths.

Thus, all nodes except the destination forward a RouteRequest packet during
the route construction phase. A destination node, after receiving the first
RouteRequest packet, replies to the source node through the reverse path the
RouteRequest packet had traversed. Nodes can also learn about the neighbouring
routes traversed by data packets if operated in the promiscuous mode (the mode of
operation in which a node can receive the packets that are neither broadcast nor
addressed to itself). This route cache is also used during the route construction
phase.

This protocol uses a reactive approach which eliminates the need to

periodically flood the network with table update messages which are required in a
table-driven approach. In a reactive (on-demand) approach such as this, a route is
established only when it is required and hence the need to find routes to all other
nodes in the network as required by the table-driven approach is eliminated. The
intermediate nodes also utilize the route cache information efficiently to reduce the
control overhead.

The disadvantage of this protocol is that the route maintenance mechanism

does not locally repair a broken link. Stale route cache information could also result
in inconsistencies during the route reconstruction phase. The connection setup delay
is higher than in table-driven protocols. Even though the protocol performs well in
static and low-mobility environments, the performance degrades rapidly with
increasing mobility. Also, considerable routing overhead is involved due to the
source-routing mechanism employed in DSR. This routing overhead is directly
proportional to the path length.
iii.Adhoc On-Demand Distance Vector Routing (AODV)

Reactive protocols seek to set up routes on-demand. If a node wants to initiate

communication with a node to which it has no route, the routing protocol will try to
establish such a route. The Ad-Hoc On-Demand Distance Vector routing protocol is
described in RFC 3561. The philosophy in AODV, like all reactive protocols, is that
topology information is only transmitted by nodes on-demand. When a node wishes
to transmit traffic to a host to which it has no route, it will generate a route
request(RREQ) message that will be flooded in a limited way to other nodes.

This causes control traffic overhead to be dynamic and it will result in an initial delay
when initiating such communication. A route is considered found when the RREQ
message reaches either the destination itself, or an intermediate node with a valid
route entry for the destination. For as long as a route exists between two endpoints,
AODV remains passive. When the route becomes invalid or lost, AODV will again
issue a request.

AODV avoids the ``counting to infinity'' problem from the classical distance vector
algorithm by using sequence numbers for every route. The counting to infinity
problem is the situation where nodes update each other in a loop. Consider
nodes A, B, C and D making up a MANET. A is not updated on the fact that its route
to D via C is broken. This means that A has a registered route, with a metric of 2,
to D. C has registered that the link to D is down, so once node B is updated on the
link breakage between C and D, it will calculate the shortest path to D to be
via A using a metric of 3. C receives information that B can reach D in 3 hops and
updates its metric to 4 hops. A then registers an update in hop-count for its route
to D via C and updates the metric to 5. And so they continue to increment the metric
in a loop.
 The way this is avoided in AODV, for the example described, is by B noticing
that As route to D is old based on a sequence number. B will then discard the route
and C will be the node with the most recent routing information by which B will
update its routing table.

AODV defines three types of control messages for route maintenance:

RREQ - A route request message is transmitted by a node requiring a route to a node.

As an optimization AODV uses an expanding ring technique when flooding these
messages. Every RREQ carries a time to live (TTL) value that states for how many hops
this message should be forwarded. This value is set to a predefined value at the first
transmission and increased at retransmissions. Retransmissions occur if no replies are
received. Data packets waiting to be transmitted(i.e. the packets that initiated the
RREQ) should be buffered locally and transmitted by a FIFO principal when a route is
set.

RREP - A route reply message is unicasted back to the originator of a RREQ if the
receiver is either the node using the requested address, or it has a valid route to the
requested address. The reason one can unicast the message back, is that every route
forwarding a RREQ caches a route back to the originator.
RERR - Nodes monitor the link status of next hops in active routes. When a link
breakage in an active route is detected, a RERR message is used to notify other
nodes of the loss of the link. In order to enable this reporting mechanism, each node
keeps a ``precursor list'', containing the IP address for each its neighbors that are
likely to use it as a next hop towards each destination.
 Node A wishes to initiate traffic to node J for which it has no route. A
broadcasts a RREQ which is flooded to all nodes in the network. When this request is
forwarded to J from H, J generates a RREP. This RREP is then unicasted back to A
using the cached entries in nodes H, G and D.

VEHICULAR ADHOC NETWORKS (VANET)

Vehicular Ad hoc Network (VANET), a subclass of mobile Ad Hoc networks

(MANETs), is a promising approach for future intelligent transportation system (ITS).
These networks have no fixed infrastructure and instead rely on
the vehicles themselves to provide netw ork functionality. However, due to mobility
constraints, driver behavior, and high mobility, VANETs exhibit characteristics that
are dramatically different from many generic MANETs.

Networking Properties of VANET

VANETs are an instantiation of a Mobile Ad Hoc networks (MANETs). MANETs

have no fixed infrastructure and instead rely on ordinary nodes to perform routing of
messages and network management functions. However, Vehicular Ad Hoc networks
behave in fundamentally different ways than the models that predominate MANET
research. Driver behavior, constraints on mobility, and high speeds create unique
Characteristics in IVC networks. These characteristics have important implications for
design decisions in these networks. The major differences are as follows. a) Rapid
changes in the VANETs topology are difficult to manage. Due to high relative speed
between cars network's topology changes very fast. b) The IVC network is subject to
frequent fragmentation, even at a high rate of IVC deployment. Although the
connectivity characteristic of MANETs has been studied broadly, there is few research
which tries to tackle this problem. It is mostly because VANET's connectivity depends
on the scenario. Of course being connective for VANETs is not important for
emergency safety messages since while the network is not connected there is no
problem in safety point of view. c) The IVC network has small effective network
diameter. Rapid changes in connectivity cause many pas to disconnect before they
can be utilized.

This characteristic is important for mostly comfort application as they need to

establish unicast and multicast routes (e.g., to the internet gateway). d) No significant
power constraints, unlike sensor and other types of mobile networks where limited
battery life is a major concern. Potentially large-scale: In a city center or highways at
the entrance of big cities the network could be quite large scale. Variable Network
density: the network's density depends on vehicular density which is highly variable.
In traffic jam situations the network can be categorized in very dense networks in
suburban traffics it could be a sparse network. g) The topology of the network could
be affected by driver's behavior due to his/her reaction to the messages. In other
words the content of messages can change net-work's topology.

Safety Applications

Examples of vehicle-to-vehicle safety communication may include collision

waning, road obstacle warning, cooperative driving, intersection collision warning,
and lane change assistance. There are two types of safety messages in the control
channel (e.g., of DSRC) and can be classified depending on how they are generated:
event driven and periodic. The first ones are the result of the detection of an unsafe
situation, (eg., a car crash, the proximity of vehicles at high speed, etc). Periodic
messages instead can be seen as preventive messages in terms of safety, and their
information can also be used by other (non-safety) applications (e.g., traffic
monitoring) or protocols (e.g., routing).

Periodic message exchange (also called beaconing) is needed to make vehicles

aware of their environment. Thus, they will be able to avoid emergency or unsafe
situations even before they appear. Therefore beacon messages essentially contain
the stat of the sending vehicle, i.e., position, direction, speed, etc., and also
aggregated data regarding the state of their neighbors. It is reasonable to assume
that these periodic messages will be sent in a broadcast fashion since the messages'
content can be beneficial for all vehicles around. In the following we come to debate
the previous related works attempting to providing safety applications. MAC Layer

Issues.: As mentioned before, event driven messages should have higher

priority than periodic and comfort messages. Thus some mechanisms for service
differentiation and admission control are needed. In the other words, we could
define the levels of priority. event driven safety messages, beacon safety messages
and comfort messages, in decreasing order.

These mechanisms are highly depended on MAC layer policy. Therefore in the
first step the research and industry should standardized a standard for MAC layer in
VANETs. There are some promising MAC techniques for future VANETs . Currently
IEEE 802.1 la is chosen by ASTM (American Society for Testing and Materials) to be
basis for its standard of DSRC and IEEE P 1609 Working Group is proposing DSRC as
IEEE 802.11p standard .

However MAC layers based on UTRA TDD , promoted by CarTALK can be another
alternative. Also still some efforts are running on Time Division Multiple Access
(TDMA). Message Dissemination: Due to specific characteristics of safety messages,
broadcasting could be the only possible way for message exchange. So it could be
possible to get complete coverage to all relevant vehicles. Message forwarding can
help warning message reach vehicles beyond the radio transmission.

MANET vs VANET

MANET is the short form of Mobile AdHoc Network. In ad-hoc networks all
the nodes are mobile in nature and hence they can be interfaced dynamically in
arbitrary fashion. As we know any wireless transmission has distance coverage
limitation, wireless node will utilize its neighbouring nodes to transmit the packet
beyond its distance limitation. To overcome this limitation, MANET nodes require ad-
hoc type routing protocols. They are of two types viz. table driven routing protocols
and On demand routing protocols.
Following are the features of MANET network:

• Dynamic topologies

• variable capacity links

• Energy constrained operation

• Limited physical security

VANET is the short form of Vehicular Adhoc Network. It is subclass of network

of MANET type. The routing protocols of MANET are not feasible to be used in the
VANET network. If they are used then also they will not be able to deliver required
throughput as it has fast changing adhoc network.

In VANET, the communication nodes are moving on pre-defined roads as

finalized initially.
The VANET architecture consists of three type of categories as mentioned below:

• cellular and WLAN network

• Pure Ad hoc (network between vehicles and fixed gateways)

• hybrid(combination of both infrastructure and adhoc networks), as shown in figure.

In the first type, fixed gateways and WiMaX/WiFi APs are used at traffic
junctions to connect with the internet, to obtain traffic information and used for
routing. The VANET nodes are not subject to storage and power limitation.

MANETs are a kind of wireless ad hoc networks that usually has a routable
networking environment on top of a Link Layer ad hoc network. A mobile ad-hoc
network (MANET) is a self-configuring infrastructure- less network of mobile devices
connected by wireless. Each device in a MANET is free to move independently in any
direction, and will therefore change its links to other devices frequently . Vehicular
Ad hoc Network (VANET) is a subclass of mobile Ad Hoc networks (MANETs). These
networks have no fixed infrastructure and instead rely on the vehicles themselves to
provide network functionality.

These networks offer several benefits to organizations of any size. While such
a network does pose certain safety concerns but this does not limit VANET‘s potential
as a productivity tool. GPS and navigation systems can benefit, as they can be
integrated with traffic reports to provide the fastest route to work.

SECURITY

Among all the challenges of the VANET, security got less attention so far. VANET
packets contains life critical information hence it is necessary to make sure that these
packets are not inserted or modified by the attacker; likewise the liability of drivers
should also be established that they inform the traffic environment correctly and
within time. These security problems do not similar to
general communication network. The size of network, mobility, geographic
relevancy etc makes the implementation difficult and distinct from other network
security.

Security Challenges in VANET

The challenges of security must be considered during the design of VANET

architecture, security protocols, cryptographic algorithm etc. The following list
presents some security challenges:

Real time Constraint: VANET is time critical where safety related message should
be delivered with 100ms transmission delay. So to achieve real time constraint, fast
cryptographic algorithm should be used. Message and entity authentication must be
done in time.

Data Consistency Liability: In VANET even authenticate node can perform

malicious activities that can cause accidents or disturb the network. Hence a
mechanism should be designed to avoid this inconsistency. Correlation among the
received data from different node on particular information may avoid this type of
inconsistency.

Low tolerance for error: Some protocols are designed on the basis of probability.
VANET uses life critical information on which action is performed in very short time. A
small error in probabilistic algorithm may cause harm.

Key Distribution: All the security mechanisms implemented in VANET dependent on

keys. Each message is encrypted and need to decrypt at receiver end either with
same key or different key. Also different manufacturer can install keys in different
ways and in public key infrastructure trust on CA become major issue. Therefore
distribution of keys among vehicles is a major challenge in designing a security
protocols.

Incentives: Manufactures are interested to build applications that consumer likes

most. Very few consumers will agree with a vehicle which automatically reports any
traffic rule violation. Hence successful deployment of vehicular networks will require
incentives for vehicle manufacturers, consumers and the government is a challenge
to implement security in VANET.

High Mobility: The computational capability and energy supply in VANET is same as
the wired network node but the high mobility of VANET nodes requires the less
execution time of security protocols for same throughput that wired network
produces. Hence the design of security protocols must use the approaches to reduce
the execution time. Two approaches can be implementing to meet this requirement.

Low complexity security algorithms: Current security protocols such as SSL/TLS,

DTLS, WTLS, generally uses RSA based public key cryptography. RSA algorithm uses
the integer factorisation on large prime no. which is NP-Hard. Hence decryption of
the message that used RSA algorithm becomes very complex and time consuming.
Hence there is need to implement alternate cryptographic algorithm like Elliptic
curve cryptosystems and lattice based cryptosystems. For bulk data encryption AES
can be used.

Transport protocol choice: To secure transaction over IP, DTLS should be preferred
over TLS as DTLS operates over connectionless transport layer. IPSec which secures IP
traffic should be avoided as it requires too many messages to set up. However IPSec
and TLS can be used when vehicles are not in motion.

Security requirements in VANET

VANET must satisfy some security requirements before they are deployed. A
security system in VANET should satisfy the following requirements:

Authentication: Authentication ensures that the message is generated by the

legitimate user. In VANET a vehicle reacts upon the information came from the other
vehicle hence authentication must be satisfied.
Availability: Availability requires that the information must be available to the
legitimate users. DoS Attacks can bring down the network and hence information
cannot be shared.

Non-Repudiation: Non-repudiation means a node cannot deny that he/she does not
transmit the message. It may be crucial to determine the correct sequence in crash
reconstruction.

Privacy: The privacy of a node against the unauthorised node should be guaranteed.
This is required to eliminate the massage delay attacks.

Data Verification: A regular verification of data is required to eliminate the false

messaging.

Attackers on Vehicular Network

To secure the VANET, first we have to discover who are the attacker, their
nature, and capacity to damage the system. On the basis of capacity these attackers
may be three type •

Insider and Outsider: Insiders are the authenticated members of network whereas
Outsiders are the intruders and hence limited capacity to attack.

Malicious and Rational: Malicious attackers have not any personal benefit to attack;
they just harm the functionality of the network. Rational attackers have the personal
profit hence they are predictable.

Active and Passive: Active attackers generate signals or packet whereas passive
attackers only

sense the network.

Attacks in the VANET

To get better protection from attackers we must have the knowledge about the
attacks in VANET against security requirements. Attacks on different security
requirement are given below:
Impersonate: In impersonate attack attacker assumes the identity and privileges of
an authorised node, either to make use of network resources that may not be
available to it under normal circumstances, or to disrupt the normal functioning of
the network. This type of attack is performed by active attackers.

They may be insider or outsiders. This attack is multilayer attack means

attacker can exploit either network layer, application layer or transport layer
vulnerability. This attack can be performed in two ways: a) False attribute possession:
In this scheme an attacker steals some property of legitimate user and later with the
use of attribute claims that it is who (legitimate user) that sent this message. By using
this type attack a normal vehicle can claim that he/she is a police or fire protector to
free the traffic. b) Sybil: In this type of attack, an attacker use different identities at
the same time.

Session hijacking: Most authentication process is done at the start of the session.
Hence it is easy to hijack the session after connection establishment. In this attack
attackers take control of session between nodes.

Identity revealing: Generally a driver is itself owner of the vehicles hence getting
owner‘s identity can put the privacy at risk.

Location Tracking: The location of a given moment or the path followed along a
period of time can be used to trace the vehicle and get information of driver.

Repudiation: The main threat in repudiation is denial or attempt to denial by a node

involved in communication. This is different from the impersonate attack. In this
attack two or more entity has common identity hence it is easy to get
indistinguishable and hence they can be repudiated.
Eavesdropping: Eavesdropping is a most common attack on confidentiality. This
attack is belongs to network layer attack and passive in nature. The main goal of this
attack is to get access of confidential data. • Denial of Service: DoS attacks are most
prominent attack in this category. In this attack attacker prevents the legitimate user
to use the service from the victim node. DoS attacks can be carried out in many ways.

a) Jamming: In this technique the attacker senses the physical channel and gets
the information about the frequency at which the receiver receives the signal. Then
he transmits the signal on the channel so that channel is jam.

b) SYN Flooding: In this mechanism large no of SYN request is sent to the victim
node, spoofing the sender address. The victim node send back the SYN-ACK to the
spoofed address

but victim node does not get any ACK packet in return. This result too half opens
connection to handle by a victim node‘s buffer. As a consequence the legitimate
request is discarded.
c) Distributed DoS attack: This is another form Dos attack. In this attack, multiple
attackers attack the victim node and prevents legitimate user from accessing the
service.

Routing attack: Routing attacks re the attacks which exploits the vulnerability of
network layer routing protocols. In this type of attack the attacker either drops the
packet or disturbs the routing process of the network. Following are the most
common routing attacks in the VANET:

a) Black Hole attack: In this type of attack, the attacker firstly attracts the nodes to
transmit the packet through itself. It can be done by continuous sending the
malicious route reply with fresh route and low hop count. After attracting the node,
when the packet is forwarded through this node, it silently drops the packet.

b) Worm Hole attack: In this attack, an adversary receives packets at one point in
the network, tunnels them to another point in the network, and then replays them
into the network from that point. This tunnel between two adversaries are called
wormhole. It can be established through a single long-range wireless link or a wired
link between the two adversaries. Hence it is simple for the adversary to make the
tunnelled packet arrive sooner than other packets transmitted over a normal multi-
hop route.

c) Gray Hole attack: This is the extension of black hole attack. In this type of attack
the malicious node behaves like the black node attack but it drops the packet
selectively. This selection can be of two type:

i) A malicious node can drop the packet of UDP whereas the TCP packet will be
forwarded.

ii) The malicious node can drop the packet on the basis of probabilistic
distribution.

UNIT - V

MOBILE DEVICE OPERATING SYSTEMS

A mobile operating system (or mobile OS) is an operating system for smart phones,
tablets, PDAs, or other mobile devices. While computers such as the typical laptop are
mobile, the operating systems usually used on them are not considered mobile ones as
they were originally designed for bigger stationary desktop computers that historically
did not have or need specific "mobile" features. This distinction is getting blurred in
some newer operating systems that are hybrids made for both uses.
Mobile operating systems combine features of a personal computer operating system
with other features useful for mobile or handheld use; usually including, and most of
the following considered essential in modern mobile systems; a touch screen, cellular,
Bluetooth, Wi-Fi, GPS mobile navigation, camera, video camera, speech recognition,
voice recorder,music player, near field communication and infrared blaster.
Mobile devices with mobile communications capabilities (e.g. smartphones) contain
two mobile operating systems – the main user-facing software platform is
supplemented by a second low-level proprietary real-time operating system which
operates the radio and other hardware. Research has shown that these low-level
systems may contain a range of security vulnerabilities permitting malicious base
stations to gain high levels of control over the mobile device

A mobile operating system, also called a mobile OS, is an operating system that is
specifically designed to run on mobile devices such as mobile phones, smartphones,
PDAs, tablet computers and other handheld devices. The mobile operating system is
the software platform on top of which other programs, called application programs,
can run on mobile devices.

SPECIAL CONSTRAINTS AND REQUIREMENTS

Design and capabilities of a Mobile OS (Operating System) is very different than

a general purpose OS running on desktop machines

Physically Constrained

 Battery-powered device

 Small screens of varying shapes, sizes, and resolutions

 Memory

 Storage space

Working in Uncertainty

 Networks come and go


  Other devices appear and disappear

 OS need to provide robust methods for handling connections and coping with
service interruptions and ad hoc attempts to communicate

Today's mobile devices are multifunctional devices capable of hosting a broad range
of applications for both business and consumer use. Smartphones and tablets enable
people to use their mobile device to access the Internet for email, instant messaging,
text messaging and Web browsing, as well as work documents, contact lists and
more.

Mobile devices are often seen as an extension to your own PC or laptop, and in some
cases newer, more powerful mobile devices can even completely replace PCs. And
when the devices are used together, work done remotely on a mobile device can be
synchronized with PCs to reflect changes and new information while away from the
computer.
Much like the Linux or Windows operating system controls your desktop or laptop
computer, a mobile operating system is the software platform on top of which other
programs can run on mobile devices.
A mobile operating system, also called a mobile OS, is an operating system that is
specifically designed to run on mobile devices such as mobile phones, smartphones,
PDAs, tablet computers and other handheld devices.

COMMERCIAL MOBILE OPERATING SYSTEM

Many people have ample knowledge about different mobile phones and their
companies, but a very few of them know something about operating systems. It is
vital to learn about different mobile OS used by many companies so that you can
know that what is behind your smartphone‘s smooth and colorful touchscreen.
 Above is the popularity graph, which represents last 12 months trends. It is
apparent that Android is beating up all other operating systems, even the IOS.
Symbian, which was once an industry leader, is also observing a diminishing slope.
IOS might continue to compete Android, and with the release of Windows Phone 8,
we might see some healthy competition in future.

Comparison Of Top Mobile OS

Symbian

Symbian OS is officially the property of Nokia. It means that any other company will
have to take permission from Nokia before using this operating system. Nokia has
remained a giant in the low-end mobile market, so after Java Symbian was the most
used in the mobile phones till a couple of years ago. Still Symbian is widely used in
low-end phones but the demand rate has ben continuously decreasing. By upgrading
Symbian mobile OS, Nokia has made it capable to run smartphones efficiently.
Symbian ANNA and BELLE are the two latest updates that are currently used in
Nokia‘s smartphones. Overall, the Symbian OS is excellently designed and is very
user-friendly.

Unfortunately, Symbian OS graph is going downwards nowadays due to the immense

popularity of Android and iOS. Some of the phones currently running on Symbian OS
are Nokia C6-01, Nokia 603, Nokia 700, Nokia 808 Pure View, Nokia E6 (ANNA) and
Nokia 701 (BELLE). Symbian is a popular choice among Nokia dual sim mobile phones
as well.
Android

September 20th, 2008 was the date when Google released the first Android OS
by the name of ‗Astro‘. After sometime next upgraded versions ‗Bender‘ and
‗Cupcake‘ were also released. Google then adopted the trend of naming Android
versions after any dessert or a sweet in alphabetical order. The other releases are
Donut, Éclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwich and Jelly
Bean.Marshmallow (Android 6.0) is so far the latest Android version from Google.

Since the platform is not closed like iOS, there are too many great Android apps built
by developers. Just after stepping into the smartphone and tablets market Android
gained immense popularity due to its beautiful appearance and efficient working.
Many new features were introduced which played a significant role in Android‘s
success. Google Play is an official app market that contains millions of different apps
for Android devices. Samsung, HTC, Motorola and many other top manufacturers are
using Android in their devices. Currently, Android is one of the top operating systems
and is considered serious threat for iPhone.

Some of the smartphones operating on Android are HTC Desire, Samsung Galaxy Gio,
Motorola Droid Razr, Samsung Galaxy S3 and HTC Wildfire.
Apple iOS

iOS was introduced in 29th June 2007 when the first iPhone was developed. Since then
iOS has been under gone many upgrades and currently the latest one is the iOS 9.
Apple has still not allowed any other manufacturer to lay hands on its operating
system. Unlike Android, Apple has more concentrated on the performance along
with appearance. This is the reason that the basic appearance of iOS is almost the
same as it was in 2007. Overall it is very user-friendly and is one of the mobile
best operating systems in the world. So far iOS has been used in all iPhones, iPod &
iPad.

Blackberry OS

Blackberry OS is the property of RIM (Research In Motion) and was first released in
1999. RIM has developed this operating system for its Blackberry line of
smartphones. Blackberry is much different from other operating systems. The
interface style, as well as the Smartphone design, is also different having a trackball
for moving on the menu and a qwerty keyboard.

Like Apple, Blackberry OS is a close source OS and is not available for any other
manufacturer. Currently, the latest release of this operating system isBlackberry OS
7.1 which was introduced in May 2011 and is used inBlackberry Bold 9930. It is a very
reliable OS and is immune to almost all the viruses.

Some of the smartphones operating on Blackberry OS are Blackberry Bold, Blackberry

Curve, Blackberry Torch and Blackberry 8520.
Windows OS

All of you will be familiar with Windows OS because it is used in computers all
over the world. Windows OS has also been used in mobile phones, but normal mobile
phone users find it a bit difficult to operate it but at the same time it was very
popular among people who were used to it.
 This was the case until Nokia and Microsoft joined hands to work together. The
latest Windows release by Microsoft is known as Windows 7 which has gained
immense popularity among all kind of users. With its colorful and user-friendly
interface, it has given Windows OS a new life and is currently in demand all over the
world. Another reason behind its success is that this latest OS is used in very powerful
devices made by Nokia. The computer like look has totally vanished from the
windows phones with the release of Windows 7. Samsung and HTC also released
some Windows-based phones, but they could not many places in the market.

Nokia Lumia series is completely windows based. Some of the latest Windows Phones
are Nokia Lumia 800, Nokia Lumia 900, Samsung Focus and HTC Titan 2.
BADA
Like others, Samsung also owns an operating system that is known as BADA. It is
designed for mid-range and high-end smartphones. Bada is a quiet user-friendly and
efficient operating system, much like Android, but unfortunately Samsung did not use
Bada on a large scale for unknown reasons.

The latest version Bada 2.0.5 was released on March 15th, 2012. There are only three
phones that are operating on Bada. These three smartphones are Samsung Wave,
Samsung Wave 2 and Samsung Wave 3. I believe that Bada would have achieved
much greater success if Samsung had promoted it properly.

Palm OS (Garnet OS)

Palm OS was developed by Palm Inc in 1996 especially for PDAs (Personal Digital
Assistance). Palm OS was designed to work on touchscreen GUI. Some Years later it
was upgraded and was able to support smartphones. Unfortunately, it could not
make a mark on the market and currently is not being used in any of the latest top
devices.

It has been 5 and half years since we saw the latest update of Palm OS in 2007. Palm
OS was used by many companies including Lenovo, Legend Group, Janam, Kyocera
and IBM.
Open WebOS

Open WebOS also known as Hp WebOS or just WebOS which was developed by
Palm Inc but after some years it became the property of Hewlett-Packard. WebOS
was launched in 2009 and was used in a number of smartphones and tablets.

Hp promoted WebOS at a very high level by using it in high-end smartphones and

tablets. The latest device working on WebOS was the Hp Touch Pad. With the
introduction of Android in the market sales of Hp WebOS, based tablets got very less.
At last Hp announced to discontinue WebOS-based devices, but the existing users
were assured that they will get regular updates of the operating system.
Maemo

Nokia and Maemo Community joined hands to produce an operating system

for smartphones and internet tablets, known as Maemo. Like other devices, the user
interface of Maemo also comprised of a menu from which the user can go to any
location.

Like today‘s Android the home screen is divided into multiple sections that show
Internet Search bar, different shortcut icons, RSS Feed and other such things. Later in
2010 at the MWC (Mobile World Congress) it was revealed that now Maemo project
will be merged with Mobilin to create a fresh operating system known as MeeGo.
MeeGo

MeeGo was called a mobile platform, but it was designed to run multiple electronic
devices including handhelds, in-car devices, television sets, and net books. All the
devices on which MeeGo can have the same core but the user interface is entirely
different according to the device.

In 2010, Moorestown Tablet PC was introduced at COMPUTEX Taipei, which was also
a MeeGo powered device.Most of you will have heard the name Nokia N9, but you
will not be aware of the fact that this large selling device is operating on MeeGo.
Verdict

These ten are not the only mobile operating systems out there; there are tons
more, and we shall be seeing one by Firefox mobile OS <Source> in future as well.
Firefox, which once dominated the internet browser market, is in the process of
building their web OS for mobiles, so in the future mobile OS market might get even
more competitive.

SOFTWARE DEVELOPMENT KIT: iOS,

ANDROID,BLACKBERRY,WINDOWS PHONE

iOS
iOS (originally iPhone OS) is a mobile operating system created and developed by
Apple Inc. and distributed exclusively for Apple hardware. It is the operating system
that presently powers many of the company's mobile devices, including the iPhone,
iPad, and iPod touch. In October 2015, it was the most commonly used mobile
operating system, in a few countries, such as in Canada, the United States, the United
Kingdom, Norway, Sweden, Denmark, Japan, and Australia, while iOS is far behind
Google's Android globally; iOS had a 19.7% share of the smartphone mobile
operating system units shipped in the fourth quarter of 2014, behind Android with
76.6%.However, on tablets, iOS is the most commonly used tablet operating system
in the world, while it has lost majority in many countries (e.g. the Africa continent
and briefly lost Asia).

Originally unveiled in 2007, for the iPhone, it has been extended to support other
Apple devices such as the iPod Touch (September 2007), iPad(January 2010), iPad
Mini (November 2012) and second-generation Apple TV onward (September 2010).
As of January 2015, Apple's App Store contained more than 1.4 million iOS
applications, 725,000 of which are native for iPads. These mobile apps have
collectively been downloaded more than 100 billion times.

The iOS user interface is based on the concept of direct manipulation, using multi-
touch gestures. Interface control elements consist of sliders, switches, and buttons.
Interaction with the OS includes gestures such as swipe, tap,pinch, and reverse pinch,
all of which have specific definitions within the context of the iOS operating system
and its multi-touch interface. Internal accelerometers are used by some applications
to respond to shaking the device (one common result is the undo command) or
rotating it in three dimensions (one common result is switching from portrait to
landscape mode).

iOS shares with OS X some frameworks such as Core Foundation and Foundation Kit;
however, its UI toolkit is Cocoa Touch rather than OS X's Cocoa, so that it provides
the UIKit framework rather than the AppKit framework. It is therefore not compatible
with OS X for applications. Also while iOS also shares the Darwin foundation with OS
X, Unix-like shell access is not available for users and restricted for apps, making iOS
not fully Unix-compatible either.

Major versions of iOS are released annually. The current release, iOS 9.1, was
released on October 21, 2015. In iOS, there are four abstraction layers: the Core OS
layer, the Core Services layer, the Media layer, and the Cocoa Touch layer. The
current version of the operating system (iOS 9), dedicates around 1.3 GB of the
device's flash memory for iOS itself. It runs on theiPhone 4S and later, iPad 2 and
later, iPad Pro, all models of the iPad Mini, and the 5th-generation iPod Touch and
later.

Android

Android is a mobile operating system (OS) currently developed by Google, based on

the Linux kernel and designed primarily for touch screen mobile devices such as
smart phones and tablets. Android's user interface is mainly based on direct
manipulation, using touch gestures that loosely correspond to real-world actions,
such as swiping, tapping and pinching, to manipulate on-screen objects, along with a
virtual keyboard for text input.

In addition to touch screen devices, Google has further developed Android TV for
televisions, Android Auto for cars, and Android Wear for wrist watches, each with a
specialized user interface. Variants of Android are also used on notebooks, game
consoles, digital cameras, and other electronics. As of 2015, Android has the largest
installed base of all operating systems.

Initially developed by Android, Inc., which Google bought in 2005, Android was
unveiled in 2007, along with the founding of the Open Handset Alliance – a
consortium of hardware, software, and telecommunication companies devoted to
advancing open standardsfor mobile devices. As of July 2013, the Google Play store
has had over one million Android applications ("apps") published, and over 50
billion applications downloaded. An April–May 2013 survey of mobile application
developers found that 71% of developers create applications for Android, and a 2015
survey found that 40% of full-time professional developers see Android as their
priority target platform, which is comparable to Apple's iOS on 37% with both
platforms far above others.

At Google I/O 2014, the company revealed that there were over one billion active
monthly Android users, up from 538 million in June 2013. Android's source code is
released by Google under open source licenses, although most Android devices
ultimately ship with a combination of open source and proprietary software,
including proprietary software required for accessing Google services. Android is
popular with technology companies that require a ready-made, low-cost and
customizable operating system for high-tech devices.

Its open nature has encouraged a large community of developers and enthusiasts to
use the open-source code as a foundation for community-driven projects, which add
new features for advanced users or bring Android to devices originally shipped with
other operating systems. At the same time, as Android has no centralised update
system most Android devices fail to receive security updates: research in 2015
concluded that almost 90% of Android phones in use had known but unpatched
security vulnerabilities due to lack of updates and support.

The success of Android has made it a target for patent litigation as part of the so-
called "smartphone wars" between technology companies.

BlackBerry
BlackBerry OS is a proprietary mobile operating system developed by BlackBerry Ltd
for its BlackBerry line of smart phone handheld devices. The operating system
provides multitasking and supports specialized input devices that have been adopted
by BlackBerry Ltd. for use in its handhelds, particularly the track wheel, trackball, and
most recently, the trackpad and touch screen.

The BlackBerry platform is perhaps best known for its native support for corporate
email, through MIDP 1.0 and, more recently, a subset of MIDP 2.0, which allows
complete wireless activation and synchronization with Microsoft Exchange, Lotus
Domino, or Novell

GroupWise email, calendar, tasks, notes, and contacts, when used with BlackBerry
Enterprise Server. The operating system also supports WAP 1.2. Updates to the
operating system may be automatically available from wireless carriers that support
the BlackBerry over the air software loading (OTASL) service.

Third-party developers can write software using the available BlackBerry APIclasses,
although applications that make use of certain functionality must be digitally signed.
Research from June 2011 indicated that approximately 45% of mobile developers
were using the platform at the time of publication. BlackBerry OS was discontinued
after the release of BlackBerry 10, but BlackBerry will continue support for the
BlackBerry OS.

Windows Phone
Windows Phone (WP) is a family of mobile operating systems developed by Microsoft
for smart phones as the replacement successor to Windows Mobile and Zune.
Windows Phone features a new user interface derived from Metro design language.
Unlike Windows Mobile, it is primarily aimed at the consumer market rather than the
enterprise market. It was first launched in October 2010 with Windows Phone 7.
Windows Phone 8.1 was the last public release of the operating system, released to
manufacturing on April 14, 2014

Work on a major Windows Mobile update may have begun as early as 2004 under
the codename "Photon", but work moved slowly and the project was ultimately
cancelled. In 2008, Microsoft reorganized the Windows Mobile group and started
work on a new mobile operating system. The product was to be released in 2009 as
Windows Phone, but several delays prompted Microsoft to develop Windows Mobile
6.5 as an interim release.

Windows Phone was developed quickly. One result was that the new OS would not
be compatible with Windows Mobile applications. Larry Lieberman, senior product
manager for Microsoft's Mobile Developer Experience, told eWeek: "If we'd had
more time and resources, we may have been able to do something in terms of
backward compatibility." Lieberman said that Microsoft was attempting to look at the
mobile phone market in a new way, with the end user in mind as well as the
enterprise network. Terry Myerson, corporate VP of Windows Phone engineering,
said, "With the move to capacitive touch screens, away from the stylus, and the
moves to some of the hardware choices we made for the Windows Phone 7
experience, we had to break application compatibility with Windows Mobile 6.5.

STRUCTURE OF M-COMMERCE

The traditional Web interaction model evolved on desktop computers, making

its user interface assumptions uniquely suited to a desktop or laptop computer.
Mobile Web services span a range of capabilities. Mobile appliances can display many
lines of text and graphics in a single screen. Accessing Web information on these tiny
appliances falls into three categories. This approach employs manually authored page
templates for each device type and populates these templates with content from a
database.

Because of the labour required, only a small fraction of Web content in Europe
and Japan is manually authored for any particular device. In Japan, the i-mode service
provides many Web phone users with access to specifically authored compact HTML
pages. Automated techniques for re-authoring Web content have become popular
because they are cost-effective and they allow access to content that providers have
not manually authored for very small devices.

Transforming system Making Web content compatible with device formats,

transforming systems modify content to transform the structure of interacting with
the content. The Digestor system, for example, attempts to imitate an expert Web
designer faced with the task of re-authoring Web pages for PDAs . This study also
modifies the Web page layout, splitting it into multiple sub-pages and adding
navigation links so that the user can navigate the sub-pages. z Multipurpose system
M-Links is a representative of this category. Figure shows the m-Links architecture
proposed by Intel.

The three main processing components are the link engine, which creates the
navigation interface; the service manager, which creates the action interface, and the
user interface generator, which converts the interfaces into forms suitable for the
requesting device and browser. Formats include HTML, Wireless Markup Language
(WML), Handheld Device Markup Language (HDML) and Compact HTML (CHTML).

M-Commerce Framework
 Figure illustrates an m-commerce system architecture that shows how this
study combined advance technologies according to the previous works. The
architecture consists of the Web client, XML server, and back-end processing
modules. Figure 5 is depicts the operation scenario between tiny wireless devices and
servers, based on WS technologies.

Web Client WS technologies describe the specific business functionality

exposed by a company, through an Internet connection, to provide a way for another
company to use business services. WS consists of many software building blocks that
can be assembled to construct distributed applications. They are in particular defined
by their interfaces about how they describe their functionality, how they register
their presence, and how they communicate with other WS. Restated, individuals
wanting to use WS could connect to the UDDI center to search for the required
services.

The information described by the WSDL can be acquired. The users could also
use the SOAP to transfer the required information and receive the real service. This
study adopts the mobile agent technology into the architecture to mobilize this
information . WS procedures can be mastered with mobile agents. Users only need to
send simple commands of their requirements. The mobile agents perform the actions
according to these commands and interact with WS technologies.
All users must wait for the response from the service provider and then enjoy the
services. z QoS consideration An m-commerce service could be successful; the QoS
will be one of the ultimate criteria. For example, location awareness, data burst
control, and unpredictable bit error rate. Additionally, QoS combines several qualities
or properties of a service, such as availability, security properties, response time and
throughput.

Many providers compete to offer the same WS, implying that users can decide
to select providers based on the QoS to which they can commit. This observation
suggests that users and providers must be able to engage in QoS negotiation. The
interaction between users and WS providers occurs via XML-based SOAP messages. z
SOAP security Several service scenarios in which security function is provided by the
transport layer are insufficient. SOAP security is useful for application developers.

Their functionalities include end-to-end security, application independence,

transport independence, and stored message security . The code translator module
ensures that the module with correct coding for device. The security goal of a service-
oriented architecture attempts to enable trusted interactions among the roles. If
security is defined as protection against threats, a WS identifies its set of perceived
threats and propose methods of preventing threats to WS interactions.

Two parties can establish trust when they understand the risks, having
identified the threats and vulnerabilities and conferred on a set of countermeasures
and safeguards for protecting themselves in doing business. A WS architecture
implementation should allow for incremental security and QoS models facilitated by
configuring a set of environmental prerequisites to control and manage the
interactions. In addition, users can access their personal and services folders once
they have logged into the system using a pass phrase (Certificate Authority; CA).

The client also has other functions, including changing the pass phrase;
customizing the appearance of information in the personal folder, and specifying
when the client should lock information. Web Services Flow Language (WSFL) is an
XML language describing WS compositions. WSFL considers two types. The first type
specifies the appropriate usage pattern of a collection of WS, such that the resulting
composition describes how to achieve a particular business goal; typically, the result
describes a business process.
 The second type specifies the interaction pattern of a collection of WS; in this
case, the result is a description of the overall partner interactions. Object Store
creates a ‗proxy‘ object, which communicates with the actual service to process the
application request. The proxy creation and usage is transparent to the client and its
complexity shielded by the underlying WS.

XML server includes the following functionalities: transforming data in the database
into XML data; making many different XML documents according to different
Document Type Definition (DTD); and receiving requests from web server and
producing HTML files corresponding to the back-end processing modules. The study
develops a user interface generator, which uses a combination of screen template
substitution and program inheritance to produce the appropriate markup interface
for each device.

It begins by identifying the device making the request, and then determines
the appropriate type of response markup and dispatches to a markup handler. The
handler subsequently uses a screen template to help generate the content
appropriate for the device. The generator uses the same process for both the
navigation and the action interfaces, as well as a few associated screens.

Figure illustrates the operation scenario, described in the following. 1) A

mobile device sends a request to Filter and Filter relays the request to the WS via
HTTP protocol. 2) The filter authenticates the identity of the user and device, relays
the user's request to the WS and forwards authentication data to the style generator
at the same time. The style generator then determines the style-sheet to be used
according to verify received data with user data and device data. 3) When receiving
the request, the WS generates the appropriate XML documents and style sheet to
send to the rendering module. 4) When receiving the XML documents and XSLT, the
rendering module generates documents with the XML parser and XSL engine.
PROS AND CONS OF MOBILE COMMERCE

Pros:

 Increased access to user data (e.g. by requesting Facebook login).


 Better use of the screen (not inside the browser window).

 Better use of smartphone features / tools (e.g. camera, GPS).

 Can access without an internet connection, using 3G for example.

 More control on how it is being shown.

Cons:

 Apps need to be downloaded.


 Apps need to be upgraded.

 There is a low repeated usage of apps.

 Needs to be built for each platform (iOS, Android, Windows).

 Needs to be right the first time – reviews stay ―forever‖.

MOBILE PAYMENT SYSTEM AND SECURITY ISSUES

The development of smartphones has gone and replaced a few things we grew up
with: the watch, the alarm clock, the tape recorder, music players, and it seems that
very soon, we can add cash and wallets to that list. It‘s hardly a surprise. Payment
methods have been morphing through various channels: from cash to cheques, to
credit cards and debit cards, and now to online banking and mobile commerce.

Close to 10 million mobile subscribers in Japan are already paying for purchases with
their smartphones by the end of 2010, and reports are saying that the more than
$200 billion dollar mobile payment industry willl be worth a trillion by 2015.
There are 6 billion mobile phone subscriptions in the world, and more than a billion
smartphones already in the market. Perhaps it‘s just a matter of time before we
embrace the idea of losing that wallet and opting for a digital one to buy flight
tickets, lunch, coffee or even to pay the rent.

Digital Wallets

The verdict is still out on what to call these cashless wallets: digital wallet,
electronic wallet, e-wallet, virtual wallet etc but they all work the same way. By
downloading an app onto your phone, you can link the service or app account to your
bank account or payment card. With that done, you can start paying for your wares
with your digital wallet.

Paying is a Breeze

If your digital wallet is an NFC enabled Android phone, you can tap your smartphone
at the card terminal at the checkout counter, like you would your debit card. But let‘s
face it, not all Android phones carry NFC technology and it‘s hardly a strong reason
for you to consider when it comes to picking your next smartphone. But fret not,
other e-wallets, like Square Wallet, let you pay just by saying your name to the
cashier.

Systems like ERPLY allow you to check in at a store, and let the cashier identify you by
facial recognition; your purchases are then auto-deducted from your PayPal account.
Restaurants and pubs would love platforms like Tabbedout, which lets their diners
check in when they arrive, and pay for their meal anytime without needing to wait for
the bill or to bring their wallets along. All of this is made possible with smartphones
and the right apps.

Digital Wallets not only carry payment details to allow their owners to make
purchases, they also help them to better manage their loyalty cards. If your really
want to go full digital (wallet) then it only makes sense that you need not carry
around your loyalty cards either.
To cater for this, there are also apps that let users scan the information on the
barcodes of their loyalty cards, then store them up in the phone. At the checkout
counter, they can let the cashier scan the barcode displayed on their mobile screen
to ensure that they don‘t miss out on any rewards.

Loyalty Apps and Programs

But then other apps take it up a notch and become the reward platform itself.
Loyalty platforms like LevelUp, Perka and rewardjunkie! give business owners the
flexibility to customize reward programs for their loyal, paying customers, and to
engage new customers for their booming business.

For the rest of us, this means that we don‘t have to carry around stacks of
brand-specific loyalty cards that are used probably once every couple of months.
Everything is in our smartphone, including new offers, discounts and deals offered by
participating merchants.

Alternative Payment Methods

If however you are cautious with your spending and prefer to not put all your
chicken eggs in the same basket (i.e. what if you lose your smartphone?), then there
are other online payment methods to use.

Carrier or Mobile Billing

The idea is to charge all your online purchases to your phone bill and clear that
at the end of the month. The good thing with this method is that you need not even
own a smartphone to start making online purchases. Having a mobile phone is
enough as you can pay via sms. There are confirmation codes or authorization pins or
text to punch in they are intended for security purposes.

Is it Secure?
Ultimately, the security of these mobile payment systems is always at the back of our
heads. What happens if I transfer all my payment card details into the smartphone
and the unthinkable happens: someone else gets hold of my lost or stolen
smartphone?. Well, it‘s a good thing that most of these accounts, as well as your
smartphone, can be remotely deactivated or wiped out. It is a good idea to have a
passcode lock, at least to give your phone an extra layer of protection. Also, before
you start linking your sensitive data to any mobile payment platform, do take a look
at customer reviews or coverage of the platform from reliable sources first.

Resources for accepting mobile payment

To wrap up, here is a small list of resources developers can adapt to their
online business to start accepting mobile payments from their online customers.

Card io

Tired of having to punch in line after line of credit card details? You can skip
through all that with Card.io by taking a photo of your credit card, then punching in
the CVV code manually. This help reduce fraud and developers can easily join the
program by grabbing the SDK for card.io at the site.

Jumio

Here is another app that lets you take photos of your credit card as a payment
method via Netswipe. It also has a similar online ID verification tool calledNetverify,
which lets your customer‘s computer work in your favor as an ID scanning tool.

BancBox
BancBox is an all-in, one-stop solution for businesses that cater to the online
marketplace. With the payment portal in place, the business owner can receive credit
card payments, wire transfers and checks, among others. It also has a relatively low
fee of 0.5% + 30 cents per transaction for its services.
Stripe

Stripe helps developers take care of credit card payments online with a simple
JS script. It lets you build your own payment forms, and avoid PCI requirements.
Embedding the codes in the site lets Stripe to handle all your online payment needs
at 2.9% + 30 cents per successful charge.

Zooz

ZooZ gives developers 3 lines of code, which they can integrate into their
mobile applications. There is also a sandbox environment to let developers test out
transactions at no charge. Prices are locked in at 2.8% + 19 cents per transaction.

FINITE AUTOMATA

What is TOC?
In theoretical computer science, the theory of computation is the branch that deals
with whether and how efficiently problems can be solved on a model of computation,
using an algorithm. The field is divided into three major branches: automata theory,
computability theory and computational complexity theory.
In order to perform a rigorous study of computation, computer scientists work with a
mathematical abstraction of computers called a model of computation. There are
several models in use, but the most commonly examined is the Turing machine.
Automata theory
In theoretical computer science, automata theory is the study of abstract machines
(or more appropriately, abstract 'mathematical' machines or systems) and the
computational problems that can be solved using these machines. These abstract
machines are called automata.

This automaton consists of

 • states (represented in the figure by circles),

As the automaton sees a symbol of input, it makes a transition (or jump) to another
state, according to its transition function (which takes the current state and the
recent symbol as its inputs).

Uses of Automata: compiler design and parsing.

Additive inverse: a+(-a)=0

Multiplicative inverse: a*1/a=1

Universal set U={1,2,3,4,5}

Subset A={1,3}
A’ ={2,4,5}

Absorption law: AU(A ∩B) = A, A∩(AUB) = A

De Morgan’s Law:
(AUB)’ =A’ ∩ B’ (A∩B)’ = A’ U B’ Double compliment
(A’)’ =A

A ∩ A’ = Φ

Logic relations: a b = > 7a U b 7(a∩b)=7a U 7b

Relations:
Let a and b be two sets a relation R contains aXb. Relations used in TOC:

Reflexive: a = a
Symmetric: aRb = > bRa
Transition: aRb, bRc = > aRc

If a given relation is reflexive, symmentric and transitive then the relation is called
equivalence relation.

Deductive proof: Consists of sequence of statements whose truth lead us from

some initial

Additional forms of proof:

Proof of sets

Proof by contradiction
Proof by counter example

Direct proof (AKA) Constructive proof:

If p is true then q is true

Eg: if a and b are odd numbers then product is also an odd number. Odd number can
be represented as 2n+1
a=2x+1, b=2y+1
product of a X b = (2x+1) X (2y+1)
= 2(2xy+x+y)+1 = 2z+1 (odd number)
Proof by contrapositive:
The contrapositive o the statement “if H and C” is “if not C then not H.” A statement
and its contrapositive are either both true or both false, so we can prove either to
prove the other.

Figure 1.6: Steps in the “only-if” part of Theorem 1.10

To see why “If H then C” and “I not C then not H” are logically equivalent, first
observe that there are four cases to consider:
1. H and C both true
2. H true and C false
3. C true and H false
4. H and C both false

Proof by Contradiction:
H and not C implies falsehood.
That is, start by assuming both the hypothesis H and the negation of the conclusion C.
Complete the proof by showing that something known to be false follows logically
from H and not C. This form of proof is called proof by contradiction.
It often is easier to prove that a statement is not a theorem than to prove it is a
theorem. As we mentioned, if S is any statement, then the statement “S is not a
theorem” is itsel a statement without parameters, and thus can be regarded as an
observation than a
Alleged Theorem : All primes are odd. (More formally, we might say: if integer x is a
prime, then x is odd.)
DISPROOF: The integer 2 is a prime, but 2 is even.

Proof by mathematical Induction:

Languages :

The languages we consider for our discussion is an abstraction of natural languages.

That is, our focus here is on formal languages that need precise and formal
definitions. Programming languages belong to this category.

Symbols :

Symbols are indivisible objects or entity that cannot be defined. That is, symbols are
atoms of the world of languages. A symbol is any single object such as ↑ , a, 0, 1,
#, begin, or do. Usually, characters from a typical keyboard are only used as symbols.

Alphabets :

An alphabet is a finite, nonempty set of symbols. The alphabet of a language is

denoted by ∑. When more than one alphabets are considered for discussion,
subscripts may be used (e.g. ∑1, ∑2 etc) or sometimes other symbol like G may also be
introduced.
Example :
Strings or Words over Alphabet :

A string or word over an alphabet ∑ is a finite sequence of concatenated symbols ∑.

Example : 0110, 11, 001 are three strings over the binary alphabet { 0, 1 }

aab, abcb, b, cc are four strings over the alphabet { a, b, c }

It is not the case that a string over some alphabet should contain all the symbols from
the alphabet. For example, the string cc over the alphabet { a, b, c } does not contain
the symbols a and b. Hence, it is true that a string over an alphabet is also a string
over an alphabet is also a string over any superset of that alphabet.

Length of a string :

The number of symbols in a string w is called its length, denoted by | w|

Example : | 011 | = 4, |11| = 2, | b | = 1

Convention : We will use small case letters towards the beginning of the
English alphabet to denote symbols of an alphabet and small case letters towards the
end denote strings over an alphabet. That a,b,c,  (symbols) and u, v, w, x, y,z
are strings.

Some String Operations :

Example : Consider the string 011 over the binary alphabet. All the prefixes, suffixes

Prefixes: ε, 0, 01, 011. Suffixes:

ε, 1, 11, 011. Substrings: ε, 0, 1, 01, 11, 011.

Note that x is a prefix (suffix or substring) to x, for any string x and ε is a prefix (suffix
or substring) to any string.

A string x is a proper prefix (suffix) of string y if x is a prefix (suffix) of y and x ≠ y.

In the above example, all prefixes except 011 are proper

Powers of Strings : For any string x and n>=0, we use x pow(n) to denote the
string formed by sequentially concatenating n copies of x. We can also give an

Powers of Alphabets :
We write k (for some integer k) to denote the set of strings of length k with symbols
from  . In other words,
k = { w | w is a string over  and | w | = k}. Hence, for any alphabet, o denotes the
set of all strings of length zero. That o= { e }. For the binary alphabet { 0, 1 } we is,
o= {e}
1= {0,1}
2= {00,01,10,11}
3= {000,001,010, 011,100, 101,110,111}

The set of all strings over an alphabet  is denoted by *. That is,
* = 0 U 1 U 2 U……. x U …….
= U k

The set * contains all the strings that can be generated by iteratively symbols from
any number of times.

Example : If  = { a, b }, then = { ε, a, b, aa, ab, ba, bb, aaa, aab, aba, abb, baa, …}.
Convention : Capital letters A, B, C, L, etc. with or without subscripts are
normally used

Set operations on languages : Since languages are set of strings we can apply
set operations to languages. Here are some simple examples (though there is nothing
new in it).
An automata is an abstract computing device (or machine). There are different
varities

of such abstract machines (also called models of computation) which can be

Every Automaton fulfills the three basic

• Every automaton consists of some essential features as in real computers. It

has a mechanism for reading input. The input is assumed to be a sequence of
 symbols over a given alphabet and is placed on an input tape(or written on an
input file). The simpler automata can only read the input one symbol at a time
from left to right but not change. Powerful versions can both read
• The automaton can produce output of some form. If the output in response to
an input string is binary (say, accept or reject), then it is called an accepter. If it
produces an output sequence in response to an input sequence, then it is
called a transducer(or automaton with output).

• The automaton may have a temporary storage, consisting of an unlimited

number of cells, each capable of holding a symbol from an alphabet ( whcih
may be different from the input alphabet). The automaton can both read and
change the contents of the storage cells in the temporary storage. The accusing
capability of this storage varies depending on the type of the storage.
• The most important feature of the automaton is its control unit, which can be
in any one of a finite number of interval states at any point. It can change state
in some defined manner determined by a transition function.

Figure 1: The figure above shows a diagrammatic representation of a generic

automation.

Operation of the automation is defined as follows.

At any point of time the automaton is in some integral state and is reading a
particular symbol from the input tape by using the mechanism for reading input. In
the next time step the automaton then moves to some other integral (or remain in
the same state) as defined by the transition function. The transition function is based
on the current state, input symbol read, and the content of the temporary storage. At
the same time the content of the storage may be changed and the input read may be
modifed. The automation may also produce some output during this transition. The
internal state, input and the content of storage at any point defines the configuration
of the automaton at that point. The transition from one configuration to the next ( as
defined by the transition function) is called a move. Finite state machine or Finite
Automation is the simplest type of abstract machine we consider. Any system that is
at any point of time in one of a finite number of interval state and moves among
these states in a defined manner in response to some input, can be modeled by a
finite automaton.
Finite Automata
Automata (singular : automation) are a particularly simple, but useful, model of
computation. They were initially proposed as a simple model for the behavior of
neurons.
States, Transitions and Finite - State Transition System :

Let us first give some intuitive idea about a state of a system and st at e before
describing finite

Informally, a sta te o f a syste m is an instantaneous description of that system gives

all relevant information necessary to determine how the system can evolve from T
ran si t ions are changes of states that can occur spontaneously or in response to
inputs to the states. Though transitions usually take time, we assume that state
transitions

Some examples of state transition systems are: digital systems, vending machines,

A system containing only a finite number of states and transitions among them is
called

Finite-state transition systems can be modeled abstractly by a mathematical model

Deterministic Finite (-state) Automata

Informally, a DFA (Deterministic Finite State Automaton) is a simple machine that
reads an input string -- one symbol at a time -- and then, after the input has been
completely read, decides whether to accept or reject the input. As the symbols are
read from the tape, the automaton can change its state, to reflect how it reacts to
what it has seen so far. A machine for which a deterministic code can be formulated,
and if there is only one unique way to formulate the code, then the machine is called
deterministic

Thus, a DFA conceptually consists of 3 parts:

finite number of states that the machine is allowed to be in (zero or more states are
designated as accept or final states), a state transition function for changing the
current

An automaton processes a string on the tape by repeating the following actions until
the

1. The tape head reads the current tape cell and sends the symbol s found there
to the control. Then the tape head moves to the next cell.

2. The control takes s and the current state and consults the state transition

Once the entire string has been processed, the state in which the automation enters
is examined. If it is an accept state , the input string is accepted ; otherwise, the string

Deterministic Finite State Automaton : A Deterministic Finite State Automaton (DFA)

is a 5-tuple
Acceptance of Strings :

Language Accepted or Recognized by a DFA :

Extended transition function :

is the state the automation reaches when it starts from the state q finish processing
the string w. Formally, we can give an inductive definition as
The language of the DFA M is the set of strings that can take the start state to one of
the accepting states i.e.
 It is a formal description of a DFA. But it is hard to comprehend.

We can describe the same DFA by transition table or state transition diagram as
Transition Table :

It is easy to comprehend the transition

Explanation : We cannot reach find state q1 w/0 or in the i/p string. There can be any
no. of 0's at the beginning. ( The self-loop q0 on label 0 indicates it ).
Transition table :

It is basically a tabular representation of the transition function that takes two

arguments

• Rows correspond to states,

• Columns correspond to input symbols,

• Entries correspond to next states
• The start state is marked with an arrow
• The accept states are marked with a star

(State) Transition diagram :

A state transition diagram or simply a transition diagram is a directed graph which
can

1. For each state in Q there is a node.

2. There is a directed edge from node q to node p labeled a  (q.a)=p . (If there are
several input symbols that cause a transition, the edge is labeled by the list of these
symbols.)
3. There is an arrow with no source into the start state.
5.

6. Here is an informal description how a DFA operates. An input to a DFA can be any
string . Put a pointer to the start state q. Read the input string w left to right,
one symbol at a time, moving the pointer according to the transition  pointer
to (p,a) . When the end of the input string w is encountered, the is on some state, r.
The string is said to be accepted by the DFA rF and rejected if F. Note that there is
no formal mechanism for moving the A language L * pointer.
Regular Expressions: Formal Definition

We construct REs from primitive constituents (basic elements) by repeatedly applying

Definition : Let S be an alphabet. The regular expressions are defined recursively as

Basis :
Language described by REs : Each describes a language (or a language is associated
with every RE). We will see later that REs are used to attribute regular languages.

Notation : If r is a RE over some alphabet then L(r) is the language associate with r
 Precedence Rule

Consider the RE ab + c. The language described by the RE can be thought of L(a)L(b+c)

or L(ab) L(c) as provided by the rules (of languages described by given already. But
these two represents two different languages lending to ambiguity.
1) Use fully parenthesized expression- (cumbersome)

2) Use a set of precedence rules to evaluate the options of REs in some order. Like
For REs, the order of precedence for the operators is as

i) The star operator precedes concatenation and concatenation precedes union (+)

ii) It is also important to note that concatenation & union (+) operators are
associative
Using these precedence rule, we find that the RE ab+c represents the language L(ab)

We can, of course change the order of precedence by using parentheses. For

example,

Example : The RE ab*+b is grouped as ((a(b*))+b) which describes the language

L(a)(L(b))* L(b)

Example : The RE (ab)*+b represents the language  L(b).

Example : It is easy to see that the RE (0+1)*(0+11) represents the language of all

Example : The regular expression r =(00)*(11)*1 denotes the set of all strings with an
.

Solution : Every string in L(r) must contain 00 somewhere, but what comes before
and what goes before is completely arbitrary. Considering these observations we can

Example : Considering the above example it becomes clean that the RE

(0+1)*11(0+1)*+(0+1)*00(0+1)* represents the set of string over {0,1} that contains
the substring 11 or 00.

Example : Consider the RE 0*10*10*. It is not difficult to see that this RE describes
the
set of strings over {0,1} that contains exactly two 1's. The presence of two 1's in the

Example : Consider the language of strings over {0,1} containing two or more

Solution : There must be at least two 1's in the RE somewhere and what comes
before, between, and after is completely arbitrary. Hence we can write the RE as
(0+1)*1(0+1)*1(0+1)*. But following two REs also represent the same language,

i) 0*10*1(0+1)*

ii) (0+1)*10*10*

Example : Consider a RE r over {0,1} such

Solution : Though it looks similar to ex ……., it is harder to construct to

construct. We observer that, whenever a 1 occurs, it must be immediately followed
by a 0. This substring may be preceded & followed by any no of 0's. So the final RE
must be a repetition of strings of the form: 00…0100….00 i.e. 0*100*. So it looks like
the RE is (0*100*)*. But in this case the strings ending in 1 or consisting of all 0's are
not
(0*100)(1+)+0*(1+)

Alternative Solution :

The language can be viewed as repetitions of the strings 0 and 01. Hence get the RE
as 

Regular Expression and Regular Language :

Equivalence(of REs) with FA

Recall that, language that is accepted by some FAs are known as Regular language.
The two concepts : REs and Regular language are essentially same i.e. (for) every
regular language can be developed by (there is) a RE, and for every RE there is a
Regular Langauge. This fact is rather suprising, because RE approach to describing
language is fundamentally differnet from the FA approach. But REs and FA are
equivalent in their descriptive power. We can put this fact in the focus of the
following Theorem.

Theorem : A language is regular iff some RE describes it.

This Theorem has two directions, and are stated & proved below as a separate

RE to FA :

REs denote regular languages :

Lemma : If L(r) is a language described by the RE r, then it is regular i.e. there is a FA

Proof : To prove the lemma, we apply structured index on the expression r.
First, show how to construct FA for the basis elements: ϕ, and for any a. Then
we show how to combine these Finite Automata into Complex Automata that accept
the Union, Concatenation, Kleen Closure of the languages accepted by the original
Use of NFAs is helpful in the case i.e. we construct NFAs for every REs which are
Basis :
Since the start state is also the accept step, and there is no any transition defined, it
will accept the only string and nothing else.
Non-Deterministic Finite Automata

Nondeterminism is an important abstraction in computer science. Importance of

nondeterminism is found in the design of algorithms. For examples, there are many
problems with efficient nondeterministic solutions but no known efficient
deterministic solutions. ( Travelling salesman, Hamiltonean cycle, clique, etc).
Behaviour of a process is in a distributed system is also a good example of
nondeterministic situation. Because the behaviour of a process might depend on
some messages from other processes that might arrive at arbitrary times with
arbitrary contents.
It is easy to construct and comprehend an NFA than DFA for a given regular language.
The concept of NFA can also be used in proving many theorems and results. Hence, it
plays an important role in this subject.
In the context of FA nondeterminism can be incorporated naturally. That is, an NFA is

• multiple next state.

•  - transitions.

Multiple Next State :

• In contrast to a DFA, the next state is not necessarily uniquely determined by

the current state and input symbol in case of an NFA. (Recall that, in a DFA
there is symbol in  ).

 - transitions :
In an -transition, the tape head doesn't do anything- it doesnot read and it doesnot
move. However, the state of the automata can be changed - that is can go to zero, or
more states.

Acceptance :

Informally, an NFA is said to accept its input  if it is possible to start in some start
state and process , moving according to the transition rules and making choices
along way whenever the next state is not uniquely defined, such that  is completely
processed (i.e. end of  is reached), the automata is in an accept state. There may
several possible paths through the automation in response to an  since the start
state is not determined and there are choices along the way because of multiple next
automation is said to accept  if at least one computation path on  starting from at
least one start state leads to an accept state- otherwise, the automation rejects .
Alternatively, we can say that,  is accepted iff there exists a path with  from state.
Since there is no mechanism for some start state to some accept state. Since there is
no mechanism for which state to start in or which of the possible next moves to take
(including - transitions) in response to an input symbol.
Equivalence of NFA and DFA

It is worth noting that a DFA is a special type of NFA and hence the class of languages
accepted by DFA s is a subset of the class of languages accepted by NFA s.
Surprisingly, these two classes are in fact equal. NFA s appeared to have more power
than DFA s because of generality enjoyed in terms of -transition and multiple next
states. But they are no more powerful than DFA s in terms of the languages they

Converting DFA to NFA

Theorem: Every DFA has as equivalent NFA

Given any NFA we need to construct as equivalent DFA i.e. the DFA need to simulate
the behaviour of the NFA . For this, the DFA have to keep track of all the states where
the NFA could be in at every step during processing a given input string.
There are 2N possible subsets of states for any NFA with n states. Every subset
corresponds to one of the possibilities that the equivalent DFA must keep track of the
equivalent DFA will have 2N states.

The formal constructions of an equivalent DFA for any NFA is given below. We first
consider an NFA without transitions and then we incorporate the
affects  transitions later.

Formal construction of an equivalent DFA for a given NFA without  transitions.

To show that this construction works we need to show that L(D)=L(N)

We will prove the following which is a stranger statement thus

Now, given any NFA with  -transition, we can first construct an equivalent NFA
without -transition and then use the above construction process to construct an
equivalent

It is also possible to construct an equivalent DFA directly from any given NFA with -
transition by integrating the concept -closure in the above construction.
It is clear that, at every step in the processing of an input string by the DFA D , it
enters a state that corresponds to the subset of states that the NFA N could be in at
that particular point. This has been proved in the constructions of an equivalent NFA
for any If the number of states in the NFA is n , then there are 2N states in the DFA .
That is, each state in the DFA is a subset of state of the NFA .

But, it is important to note that most of these 2 N states are inaccessible from the
start state and hence can be removed from the DFA without changing the accepted
language. Thus, in fact, the number of states in the equivalent DFA would be much
than 2N.

Example : Consider the NFA given below.

Since there are 3 states in the NFA
There will be 23=8 states (representing all possible subset of states) in the DFA . The
transition table of the DFA constructed by using the subset constructions process is
produced here.
It is interesting to note that we can avoid encountering all those inaccessible or
unnecessary states in the equivalent DFA by performing the following two steps.
PROS AND CONS OF MOBILE COMMERCE

Pros:

 Increased access to user data (e.g. by requesting Facebook login).


 Better use of the screen (not inside the browser window).

 Better use of smartphone features / tools (e.g. camera, GPS).

 Can access without an internet connection, using 3G for example.

 More control on how it is being shown.

MOBILE PAYMENT SYSTEM AND SECURITY ISSUES

The development of smartphones has gone and replaced a few things we grew up
with: the watch, the alarm clock, the tape recorder, music players, and it seems that
very soon, we can add cash and wallets to that list. It‘s hardly a surprise. Payment
methods have been morphing through various channels: from cash to cheques, to
credit cards and debit cards, and now to online banking and mobile commerce.

Close to 10 million mobile subscribers in Japan are already paying for purchases with
their smartphones by the end of 2010, and reports are saying that the more than
$200 billion dollar mobile payment industry willl be worth a trillion by 2015.

There are 6 billion mobile phone subscriptions in the world, and more than a billion
smartphones already in the market. Perhaps it‘s just a matter of time before we
embrace the idea of losing that wallet and opting for a digital one to buy flight
tickets, lunch, coffee or even to pay the rent.

Digital Wallets

The verdict is still out on what to call these cashless wallets: digital wallet,
electronic wallet, e-wallet, virtual wallet etc but they all work the same way. By
downloading an app onto your phone, you can link the service or app account to your
bank account or payment card. With that done, you can start paying for your wares
with your digital wallet.

Paying is a Breeze

If your digital wallet is an NFC enabled Android phone, you can tap your smartphone
at the card terminal at the checkout counter, like you would your debit card. But let‘s
face it, not all Android phones carry NFC technology and it‘s hardly a strong reason
for you to consider when it comes to picking your next smartphone. But fret not,
other e-wallets, like Square Wallet, let you pay just by saying your name to the
cashier.

Systems like ERPLY allow you to check in at a store, and let the cashier identify you by
facial recognition; your purchases are then auto-deducted from your PayPal account.
Restaurants and pubs would love platforms like Tabbedout, which lets their diners
check in when they arrive, and pay for their meal anytime without needing to wait for
the bill or to bring their wallets along. All of this is made possible with smartphones
and the right apps.

Digital Wallets not only carry payment details to allow their owners to make
purchases, they also help them to better manage their loyalty cards. If your really
want to go full digital (wallet) then it only makes sense that you need not carry
around your loyalty cards either.

To cater for this, there are also apps that let users scan the information on the
barcodes of their loyalty cards, then store them up in the phone. At the checkout
counter, they can let the cashier scan the barcode displayed on their mobile screen
to ensure that they don‘t miss out on any rewards.

Loyalty Apps and Programs

But then other apps take it up a notch and become the reward platform itself.
Loyalty platforms like LevelUp, Perka and rewardjunkie! give business owners the
flexibility to customize reward programs for their loyal, paying customers, and to
engage new customers for their booming business.

For the rest of us, this means that we don‘t have to carry around stacks of
brand-specific loyalty cards that are used probably once every couple of months.
Everything is in our smartphone, including new offers, discounts and deals offered by
participating merchants.

Alternative Payment Methods

 If however you are cautious with your spending and prefer to not put all your
chicken eggs in the same basket (i.e. what if you lose your smartphone?), then there
are other online payment methods to use.

Carrier or Mobile Billing

The idea is to charge all your online purchases to your phone bill and clear that
at the end of the month. The good thing with this method is that you need not even
own a smartphone to start making online purchases. Having a mobile phone is
enough as you can pay via sms. There are confirmation codes or authorization pins or
text to punch in they are intended for security purposes.

Is it Secure?

Ultimately, the security of these mobile payment systems is always at the back of our
heads. What happens if I transfer all my payment card details into the smartphone
and the unthinkable happens: someone else gets hold of my lost or stolen
smartphone?. Well, it‘s a good thing that most of these accounts, as well as your
smartphone, can be remotely deactivated or wiped out. It is a good idea to have a
passcode lock, at least to give your phone an extra layer of protection. Also, before
you start linking your sensitive data to any mobile payment platform, do take a look
at customer reviews or coverage of the platform from reliable sources first.

Resources for accepting mobile payment

To wrap up, here is a small list of resources developers can adapt to their
online business to start accepting mobile payments from their online customers.

Card io

Tired of having to punch in line after line of credit card details? You can skip
through all that with Card.io by taking a photo of your credit card, then punching in
the CVV code manually. This help reduce fraud and developers can easily join the
program by grabbing the SDK for card.io at the site.

Jumio

Here is another app that lets you take photos of your credit card as a payment
method via Netswipe. It also has a similar online ID verification tool calledNetverify,
which lets your customer‘s computer work in your favor as an ID scanning tool.

BancBox
BancBox is an all-in, one-stop solution for businesses that cater to the online
marketplace. With the payment portal in place, the business owner can receive credit
card payments, wire transfers and checks, among others. It also has a relatively low
fee of 0.5% + 30 cents per transaction for its services.

Stripe

Stripe helps developers take care of credit card payments online with a simple
JS script. It lets you build your own payment forms, and avoid PCI requirements.
Embedding the codes in the site lets Stripe to handle all your online payment needs
at 2.9% + 30 cents per successful charge.

Zooz

ZooZ gives developers 3 lines of code, which they can integrate into their
mobile applications. There is also a sandbox environment to let developers test out
transactions at no charge. Prices are locked in at 2.8% + 19 cents per transaction.