Global Mobile Satellite System

GMSS stands for Global Mobile Satellite System. An artificial body which is placed in an orbit
around the earth for the purpose of communication is known as Communication satellite. GMSS is
a system which consists of various artificial communication satellites orbiting around the earth for
the purpose of communication.
A satellite network is a combination of nodes that provides communication from one point on the
Earth to another. A node in the network can be Satellite, an Earth station, or an End -user terminal or
Telephone. Satellite networks are like cellular networks, they divide the planet into cells. The
frequencies reserved for the satellite microwave communication are in gigahertz(GHz) range. Each
satellite sends and receives over two different bands. Transmission from earth to satellite is called
the Uplink. Transmission from the satellite to the earth is called the Downlink

Uplink and downlink frequencies must be different to avoid interference. Now, stations at the earth
have greater power sources than that of satellite as it has only solar power. Also, higher frequency
results in higher attenuation and to compensate with it more power is required. So, uplink uses
higher frequency to penetrate the environment.
Satellite Orbits:
Orbit
An artificial satellite needs to have an orbit, the path in which it travels around the Earth. The orbit
can be equatorial, inclined or polar.
Footprint
Satellite process microwaves with bidirectional antennas. Therefore, the signal from the satellite is
normally aimed at a specific area called the footprint.
Satellite Categories
Based on the location of the orbit, satellites can be divided into three categories as follows

GEO:
• GEO stands for Geostationary Earth Orbit.
• The communication satellites in this orbit operates at a distance of about 36000 km
above the earth’s surface and their orbital time period is about 24 hours.
• Geostationary Orbit Satellites are used for radio broadcasting.
• To ensure constant communication, the satellite must move at the same speed as the
earth, so that it seems to remain fixed above a certain spot. So such satellites are
called geostationary.
• One geostationary satellite cannot cover the whole earth. One satellite in orbit has line -
of-sight contact with vast number of stations, but the curvature of the Earth still keeps
much of the planet out of sight. It takes minimum of three satellites equidistant from
each other in geostationary Earth Orbit(GEO) to provide full global transmission.
MEO:
• MEO stands for Medium Earth Orbit.
 • The communication satellites in this orbit operates at a distance of about 5000 to
12000 km above the earth’s surface.
• These satellites are positioned between the two Van Allen belts. A satellite at this orbit
takes approximately 6 to 8 hours to circle the Earth.
• One Example of a MEO satellite system is Global Positioning System(GPS), constructed
and operated by US Department of Defense, orbiting at an altitude about 18,000 km
above the earth.
• The system consists of 24 satellites and is used for land, sea, and air navigation to
provide time and locations for vehicle and ships.
• The orbits and the locations of the satellites in each orbit are designed in such a way
that, at any time, four satellites are visible from any point on the Earth. A GPS receiver
has a almanac that tells the current position of each satellite.
• GPS is based on a principle called Trilateration(also sometimes called Triangulation).
Principle states that “On a plane, if we know our distance from three points, we know
exactly where we are.”
LEO:
• LEO stands for Low Earth Orbit.
• The communication satellites in this orbit operates at a distance of about 500 to 1200
km above the earth’s surface and their orbital time period generally ranges between 95
to 120 minutes. The Satellite has a speed of 20,000 to 25,000 km/h. Low Orbit Sate llites
makes global radio coverage possible.
• An LEO system is made of a constellation of satellites that work together as a network,
each satellite acts as a switch. Satellites that are close to each other are connected
through inter-satellite links (ISLs). A mobile system communicates with the satellite
through a user mobile link(UML). A satellite can also communicate with an Earth
station(gateway) through a gateway link(GWL).
• LEO satellites can be divided into three categories: Little LEOs, Big LEOs, and Broad
Band LEOs.
• Little LEOs operate under 1GHz. They are mostly used for low-data-rate messaging.
• Big LEOs operate between 1 and 3GHz. Globalstar and Iridium system are examples of
Big LEOs.
• Broad Band LEOs provide communication similar to fiber-optic networks. The first
broadband LEO system was Teledesic.

IRIDIUM:
• The concept of Iridium system, a 77-satellite network, was started by Motorola in 1990.
The project took 8 years to materialize.
• Finally in 1998, the service was started by 66 satellites. The original name, Iridium,
came from the name of the 77th chemical element. A more appropriate name is
Dysprosium (the name of 66th element).
• The System has 66 satellites divided into 6 orbits, with 11 satellites in each orbit. The
orbits are at an altitude of 750km.
• Iridium is designed to provide direct worldwide voice and data communication using
handheld terminals, a service similar to cellular telephony but on a global scale.
Globalstar:
• Globalstar is LEO satellite system that uses 48 satellites in six polar orbits with each
orbit hosting eight satellites. The orbits are located at an altitude of almost 1400km.
• The Globalstar system is similar to the Iridium system, the main difference is the
relaying mechanism.
• Communication between two distinct users in Iridium system requires relaying between
several satellites.
• Globalstar communication requires both satellites and earth station, which means that
ground stations can create more powerful signals.
Enterprise Networks and Virtual Networks

o Enterprise Networks refer to the infrastructure that enables systems and

applications within an organization to communicate, share information, and
run services. They can be categorized into:
▪ Local Area Networks (LANs): These networks connect systems within
a small building or room. They are commonly used for personal or
non-commercial purposes.
▪ Wide Area Networks (WANs): WANs span across buildings and
disparate geographic locations, even globally. They use different
protocols and components for data transmission.
▪ Cloud Networks: These networks leverage cloud infrastructure for
scalability and flexibility1.
o Virtual Networks are logical networks created within a physical network
infrastructure. They allow segmentation, isolation, and efficient resource
utilization. For example, virtual LANs (VLANs) separate network traffic
logically, even if devices are physically connected to the same switch.
2. Bluetooth Technology and Protocols:
o Bluetooth is a short-range wireless technology standard used for exchanging
data between fixed and mobile devices over short distances. Key points
about Bluetooth:
▪ Operates in the 2.4 GHz ISM band.
▪ Supports data, voice, and video transmission.
▪ Commonly used for wireless headphones, file sharing, and connecting
devices like smartphones and laptops.
▪ Core protocols include ACL (Asynchronous Connection-
Less) and SCO (Synchronous Connection-Oriented) links.
3. History and Evolution:
o The name “Bluetooth” was inspired by a Danish King named Harald Blatand, who
united Denmark and Norway. Similarly, Bluetooth technology unites disparate devices
for communication.
o Ericsson Mobile Communications initiated Bluetooth development in 1994.
o In 1998, Ericsson, IBM, Nokia, and Toshiba formed the Bluetooth Special Interest
Group (SIG), which published the first version of Bluetooth technology in 1999.
o Subsequent versions (up to Bluetooth 5.0) improved data exchange range and speed.
4. Architecture:
o Bluetooth networks consist of a Personal Area Network (PAN) or a “Piconet.”
o A Piconet includes a minimum of 2 and a maximum of 8 Bluetooth peer devices.
o It typically contains a single master device and up to 7 slave devices.
o Piconets facilitate data transmission based on nodes (master and slave).
▪ Additional protocols include L2CAP, RFCOMM, SDP, and more.
5. Advanced Techniques in Mobile Computing:
o 5G Connectivity: Widespread adoption of 5G networks provides faster speeds
and lower latency, enabling seamless streaming and improved performance.
o Artificial Intelligence (AI): AI techniques enhance mobile applications,
optimize resource allocation, and improve user experiences.
o Augmented Reality (AR): AR applications overlay digital content on the real
world, transforming how we interact with our surroundings.
o Mobile App Development: Continuous advancements in app development
frameworks and tools.
o Security and Privacy: Focus on securing mobile devices, data encryption, and
user privacy.
Personal Communications Services (PCS)

Personal Communications Services (PCS) refer to a broad range of wireless mobile

communication services designed to provide individual users with seamless and ubiquitous
connectivity. PCS encompasses a variety of technologies and services, including digital
cellular networks, wireless local loops, and paging services. These systems aim to offer
personalized communication experiences, enabling users to communicate through voice,
data, and multimedia applications. CS systems are characterized by their ability to support
high mobility, advanced features, and interoperability across different networks and devices.
The primary goals of PCS include:

1. Ubiquitous Access: PCS allows users to access communication services anytime,

anywhere, and in various forms. Whether you’re on the move or stationary, PCS
ensures connectivity.
2. Digital Cellular Technologies: PCS encompasses digital cellular phone technologies.
It provides an efficient and reliable way to communicate wirelessly.
3. Foundation Architecture: PCS lays the foundation for wireless communication
systems, enabling seamless connectivity and enhancing user experience.

PCS Architecture

PCS architecture in mobile computing consists of several components and services that
work together to ensure reliable and secure communication. Let’s explore these
components:
1. Mobile Stations (MS):
o MS refers to movable devices within the radio network. Examples include cell
phones, handsets, or portable devices installed in vehicles.
o Two key components of MS are:
▪ Subscriber Identity Module (SIM): SIM cards contain essential
information, including the International Mobile Subscriber Identity
(IMSI). Users protect this information with a four- to eight-digit PIN.
▪ Mobile Equipment (ME) or Mobile Terminal: ME has a unique
identifier called the International Mobile Equipment Identity (IMEI),
which manufacturers cannot modify after production.
o MS communicates with the Base Station Subsystem (BSS) via the Um
Interface.
2. Base Station Subsystem (BSS):
o BSS includes base stations (cell towers) responsible for communication with
mobile devices.
o Components of BSS:
▪ Base Transceiver Station (BTS): Manages radio communication with
mobile devices.
▪ Base Station Controller (BSC): Controls multiple BTSs and manages
handovers.
▪ Mobile Switching Center (MSC): Routes calls and manages
connections.
▪ Gateway Mobile Switching Center (GMSC): Connects to external
networks.
3. Network Infrastructure:
o The network infrastructure includes various elements such as MSCs, GMSCs,
and databases.
o It ensures seamless communication across different networks (e.g., GSM,
CDMA).
4. Signal Protocols:
o PCS relies on signal protocols for communication. These include GSM,
CDMA, and other standards.
o Protocols ensure data integrity, security, and efficient transmission.
GSM ARCHITECTURE
The Global System for Mobile Communications (GSM) is a standard developed to describe
protocols for second generation (2G) digital cellular networks. Introduced in the 1990s, GSM
set the foundation for mobile communication and is still widely used today. GSM
architecture is designed to provide seamless mobile connectivity, ensuring voice, data, and
text services. The architecture is structured into several subsystems, each with specific
functions to manage mobile communication efficiently.

1. Network Switching System (NSS):

o The NSS is the core network of GSM. It carries out call and mobility
management functions for mobile phones within the network.
o Key components within NSS include:
▪ Visitor Location Register (VLR): Keeps track of mobile subscribers’
locations within the network.
▪ Home Location Register (HLR): Stores subscriber information,
including authentication data and service profiles.
▪ Equipment Identity Register (EIR): Maintains a list of valid mobile
equipment identities (IMEIs) and helps prevent mobile equipment
theft.
▪ Authentication Center (AUC): Provides authentication and encryption
keys for secure communication.
▪ Public Switched Telephone Network (PSTN): Connects GSM to the
traditional telephone network.
2. Mobile Station (MS):
o The MS comprises user equipment and software needed for communication
with the mobile network.
o It includes:
▪ Mobile Equipment (ME): The physical device (e.g., cell phone) used by
the subscriber.
▪ Subscriber Identity Module (SIM): A removable smart card containing
subscriber-specific information, including the IMSI (International
Mobile Subscriber Identity).
o The MS communicates with the tower (base station) through a transceiver
(TRX), which handles both transmission and reception3.
3. Base Station System (BSS):
o The BSS facilitates wireless communication between user equipment (MS)
and the network.
o Components within BSS:
▪ Base Transceiver Station (BTS): Located at each tower, it handles
radio communication with mobile devices.
▪ Base Station Controller (BSC): Manages multiple BTSs. Think of BSC
as a local exchange that coordinates several towers.
o BSS ensures seamless handoffs as mobile users move from one cell
(coverage area) to another.
4. Operations and Support System (OSS):
o OSS is responsible for monitoring and controlling the GSM system.
o Components within OSS:
▪ Operation and Maintenance Center (OMC): Part of OSS, it offers cost-
effective support for GSM-related maintenance services.
Mobility management

1. is a fundamental functionality in both GSM (Global System for Mobile

Communications) and UMTS (Universal Mobile Telecommunications
System) networks.
o Mobility management facilitates mobile device operations by tracking the
physical location of subscribers. Its primary goal is to ensure that mobile
phones work seamlessly as users move within and outside the network’s
coverage area.
o Key services provided by mobility management include handling calls, Short
Message Service (SMS), and other mobile phone services.

1. Purpose of Mobility Management:

o Tracking Subscribers: Mobility management allows the network to track the
physical location of mobile subscribers. This tracking ensures that calls,
SMS, and other mobile services can be delivered to them regardless of their
movement.
o Seamless Handoffs: As mobile users move from one cell to another (within
the same network or between networks), mobility management
ensures seamless handoffs. Handoffs involve transferring an ongoing call or
data session from one base station (cell) to another without interruption.
2. Location Update Procedure:
o In a cellular network, individual cells (base stations) cover specific
geographical areas. These cells collectively form a larger coverage area.
o When a mobile device moves from one location area (covered by one base
station) to another, it performs a location update. This update informs the
network about the mobile’s new location.
o Reasons for location updates include:
▪ Switching On/Off: When a mobile is switched on or off, it may need to
perform an IMSI (International Mobile Subscriber Identity) attach or
detach location update procedure.
▪ Periodic Updates: Mobiles periodically report their location to the
network.
▪ Random Updates: When a mobile moves while not on a call, it
performs a random location update.
▪ Signal Fade: Even stationary mobiles reselect coverage from a cell in
a different location area due to signal fade.
o Thus, a subscriber has reliable access to the network and may be reached
with a call while enjoying the freedom of mobility within the entire coverage
area.
3. Mobile Not Reachable Flag:
o When a subscriber is paged (e.g., for an incoming call or SMS) and doesn’t
respond, the network marks them as absent (mobile not reachable).
o The next time the mobile performs a location update, the Home Location
Register (HLR) is updated, and the mobile not reachable flag is cleared.
4. Temporary Mobile Subscriber Identity (TMSI):
o The TMSI is the identity most commonly sent between the mobile and the
network.
o TMSI is randomly assigned by the Visitor Location Register (VLR) to every
mobile in the area when it is switched on.
o It is local to a location area, so it must be updated each time the mobile
moves to a new geographical area.
o The network can also change the TMSI of the mobile at any time
Network signaling
Network signaling is a critical component in mobile computing, facilitating communication
between various network elements to establish, maintain, and terminate connections.
Signaling protocols manage the exchange of control information required for network
operations, such as call setup, handover, authentication, and mobility management.

1. Signaling Protocols:
o Control Channels: Wireless networks use specific channels for signaling
purposes. These channels carry control information rather than user data.
o Call Setup and Teardown: When a mobile device initiates a call, signaling
messages are exchanged to set up the call (e.g., paging the recipient,
allocating resources). Similarly, when the call ends, teardown messages
ensure proper release of resources.
o Handover Signaling: During handovers (when a mobile device moves from
one cell to another), signaling ensures seamless transition without call
interruption.
o Authentication and Encryption: Signaling protocols handle authentication
(verifying the user’s identity) and encryption (securing communication).
2. Types of Signaling:
o In-Band Signaling: Control information is transmitted within the same
frequency band as user data. For example, Dual-Tone Multi-Frequency
(DTMF) tones during a phone call.
o Out-of-Band Signaling: Separate channels or frequencies are used for control
information. GSM, for instance, uses separate control channels (e.g.,
Broadcast Control Channel, Common Control Channel).
o Common Signaling Protocols:
▪ SS7 (Signaling System 7): Widely used for signaling in both wired and
wireless networks. It handles call setup, teardown, and other network
management functions.
▪ RANAP (Radio Access Network Application Part): Used in UMTS
networks for signaling between Radio Network Controllers (RNCs) and
MSCs.
▪ BSSAP (Base Station System Application Part): Used in GSM
networks for signaling between BSCs and MSCs.
3. Components Involved:
o Mobile Station (MS): Initiates signaling messages (e.g., call setup request).
o Base Transceiver Station (BTS): Handles signaling between MS and BSC.
o Base Station Controller (BSC): Manages multiple BTSs and exchanges
signaling with MSC.
o Mobile Switching Center (MSC): Responsible for call routing, handovers, and
overall network management.
o HLR (Home Location Register) and VLR (Visitor Location Register): Store
subscriber information and assist in call setup.
o AUC (Authentication Center): Generates authentication parameters.
o EIR (Equipment Identity Register): Manages valid mobile equipment
identities.
o PSTN (Public Switched Telephone Network): Connects GSM to landline
networks.
General Packet Radio Service (GPRS)
General Packet Radio Services (GPRS) is a packet-oriented mobile data standard on the 2G
and 3G cellular communication networks. It extends the capabilities of GSM networks by
enabling the transmission of data over IP-based networks, allowing for continuous and
efficient data connectivity. GPRS is often referred to as 2.5G technology, bridging the gap
between the 2G and 3G cellular systems.
1. General Packet Radio Service (GPRS):
o GPRS is an expansion of the Global System for Mobile Communication
(GSM).
o It serves as a packet-oriented mobile data standard within the GSM network,
spanning both 2G and 3G cellular communication systems.
▪ Purpose: GPRS enables continuous connections to the internet for
mobile phones and handheld devices.
▪ Packet Switching: Unlike traditional circuit-switched services, GPRS
uses packet-based technology for data transfer.
▪ Services Offered:
▪ SMS Messaging and Broadcasting
▪ Push-to-Talk over Cellular
▪ Instant Messaging and Presence
▪ Multimedia Messaging Service
▪ Point-to-Point and Point-to-Multipoint Services
▪ Protocols Supported:
▪ Internet Protocol (IP)
▪ Point-To-Point Protocol (PPP)
▪ Benefits:
▪ Mobility: Seamless voice and data communication while on
the move.
▪ Cost Efficiency: Cheaper communication compared to regular
GSM networks.
▪ Immediacy: Instant connectivity without lengthy login
sessions.
▪ Localization: Relevant data based on the user’s current
location.
▪ Easy Billing: User-friendly billing via GPRS packet
transmission.
▪ GPRS is also widely used in GPS trackers to provide real-time updates
and reliable data transmission.
2. GPRS Network Architecture:
o GPRS builds upon the existing GSM infrastructure, making maximum use of
its physical structure.
o Key components include:
▪ Mobile Station (MS): Enhanced mobile stations capable of handling
both voice calls and data packets.
▪ Base Station Controller (BSC): Includes a new component
called Packet Control Unit (PCU) for routing data signals to the
Serving GPRS Support Node (SGSN).
▪ Serving GPRS Support Node (SGSN): Responsible for packet delivery,
mobility management, localization, authentication, and billing.
▪ Gateway GPRS Support Node (GGSN): Acts as a mediator between
GPRS and external data networks, storing participant addresses and
profiles.
▪ Internal Backbone Network: An IP-based network that carries data
packets between different GSNs.
▪ Routing Area: Similar to GSM’s location area but with smaller cells.
The Wireless Application Protocol (WAP)
The Wireless Application Protocol (WAP) was designed to enable mobile devices to access internet-
based services and applications. When combined with General Packet Radio Services (GPRS), WAP
provides a framework for delivering internet content and services efficiently to mobile users. This
combination leverages GPRS’s packet-switched data capabilities and WAP’s lightweight protocols
optimized for wireless communication, making it suitable for the limited bandwidth and higher latency
of mobile networks.

1. Hierarchical Structure:
o WAP’s architecture follows a hierarchical design, similar to the TCP/IP
protocol stack.
o It consists of several layers, each serving specific functions to enable mobile
internet access.
2. WAP Protocol Stack Layers:
o Application Layer (WAE):
▪ Contains the Wireless Application Environment (WAE).
▪ Specifies mobile device specifications and content development using
languages like WML (Wireless Markup Language).
o Session Layer (WSP):
▪ Provides fast connection suspension and reconnection.
▪ Ensures efficient session management for mobile applications.
o Transaction Layer (WTP):
▪ Runs on top of UDP (User Datagram Protocol).
▪ Offers transaction support for reliable data exchange.
o Security Layer (WTLS):
▪ Ensures data integrity, privacy, and authentication.
▪ Provides secure communication over wireless networks.
o Transport Layer (WDP):
▪ Presents consistent data format to higher layers of the WAP protocol
stack.
▪ Handles data transmission between mobile devices and external
packet data networks.
3. WAP Gateway:
o When a user opens the mini-browser on a mobile device and selects a
website, the mobile device sends a URL-encoded request via the network to
a WAP gateway.
o The WAP gateway translates this WAP request into a conventional HTTP URL
request and sends it over the internet.
o The web server processes the request and sends the response back to the
mobile device through the WAP gateway in a WML file, which can be
displayed in the micro-browser.
4. Advantages of WAP:
o Operators of Wireless Networks:
▪ Enhance existing wireless data services (e.g., voicemail).
▪ Facilitate new mobile applications without major infrastructure
adjustments.
o Content Providers:
▪ Open up a market for extra applications and mobile phone features.
▪ Encourage developers to write applications using WML.
o End Users:Access web content on mobile devices, even with limited
resources.
o GPRS Architecture:GPRS builds upon the existing GSM infrastructure
o .Mobile Station (MS): Enhanced mobile stations for voice and data.
o Base Station Controller (BSC): Includes a Packet Control Unit (PCU) for routing data
signals to the Serving GPRS Support Node (SGSN).
o Serving GPRS Support Node (SGSN): Handles packet delivery, mobility management,
localization, and authentication.
o Gateway GPRS Support Node (GGSN): Bridges GPRS and external data networks.
o Internal Backbone Network: IP-based network for data exchange.
o Routing Area: Smaller cells for efficient tracking.
IEEE 802.11 standard
The IEEE 802.11 standard encompasses several amendments, each introducing
enhancements to the original specification. The most notable versions include 802.11a,
802.11b, 802.11g, 802.11n, 802.11ac, and 802.11ax, each improving speed, range, and
reliability.

1. IEEE 802.11 Architecture:

o Stations (STA): These include all devices connected to the WLAN. Stations
can be of two types:
▪ Wireless Access Point (WAP): Also known as access points (AP),
WAPs bridge connections for base stations.
▪ Clients: Examples include computers, laptops, printers, and
smartphones.
o Access Point (AP): It acts as a connection point between the wireless
medium and distributed systems.
o Distribution System (DS): The DS interconnects a set of Basic Service Sets
(BSSs) and integrated LANs to create an Extended Service Set (ESS).
o Frame: A MAC protocol data unit (PDU) used for communication.
o SSID (Service Set Identifier): The network name for a specific WLAN. All
devices on the same WLAN must use the same SSID.
o SDU (Service Data Unit): The input data unit for each layer, which can be
fragmented or aggregated to form a PDU.
o PDU (Protocol Data Unit): The output data unit sent to the corresponding
layer at the other end. Each PDU contains a layer-specific header.
o Network Interface Controller (NIC): Also known as a network interface card, it
connects devices to the network.
o Portal: Serves as a gateway to other networks.

Applications and Benefits of IEEE 802.11 in Mobile Computing

1. Wireless Internet Access: Provides high-speed internet connectivity for

mobile devices without the need for wired connections.
2. Mobile Office: Enables seamless connectivity for laptops, tablets, and
smartphones within office environments, supporting remote work and
collaboration.
3. Public Hotspots: Offers internet access in public areas such as cafes,
airports, and hotels, enhancing user mobility and convenience.
4. Smart Homes and IoT: Facilitates the integration of smart devices and IoT
applications, allowing for home automation and remote monitoring.

Security in IEEE 802.11

1. WEP (Wired Equivalent Privacy): An early security protocol that has been largely
deprecated due to significant vulnerabilities.
2. WPA (Wi-Fi Protected Access): Introduced to address WEP’s shortcomings, offering
improved security through TKIP (Temporal Key Integrity Protocol).
3. WPA2: Further enhances security with AES (Advanced Encryption Standard)
encryption. It is the current standard for securing wireless networks.
4. WPA3: The latest security protocol, providing enhanced security features such as
SAE (Simultaneous Authentication of Equals) for better protection against brute-
force attacks.
Mobile IP

Mobile IP is a protocol that allows mobile devices to move across different networks while
maintaining a permanent IP address. This capability is essential in mobile computing,
enabling continuous internet connectivity and seamless user experience without interruption
as the device changes its point of attachment to the internet.

1.Home Network-The home network is the original network to which the mobile node (MN)
is permanently assigned. The mobile node has a permanent IP address within this network,
known as the home address.

2. Home Agent (HA)-The Home Agent is a router on the home network that tracks the
location of the mobile node. It intercepts packets destined for the mobile node’s home
address and forwards them to the current location of the mobile node.

3. Foreign Network-The foreign network is any network other than the home network that
the mobile node may visit. The mobile node obtains a temporary IP address, known as the
Care-of Address, while connected to this network.

4.Foreign Agent (FA)-The Foreign Agent is a router on the foreign network that assists the
mobile node in registering its Care-of Address with the Home Agent. The Foreign Agent may
also serve as the endpoint for the tunnel from the Home Agent to the mobile node.

5.Care-of Address (CoA)-The Care-of Address is a temporary IP address assigned to the

mobile node while it is connected to a foreign network. This address can either be a Foreign
Agent Care-of Address (shared with the FA) or a Co-located Care-of Address (unique to the
MN).

6. Correspondent Node (CN)-The Correspondent Node is any node that communicates with
the mobile node. It sends packets to the mobile node's home address, unaware of the
node’s current location.

Applications of Mobile IP

1. Seamless Mobility: Allows users to maintain ongoing internet sessions (e.g.,

VoIP calls, video streams) as they move between networks.
2. Remote Access: Enables users to connect to their home network resources
from different locations without changing IP addresses.
3. Mobile VPNs: Enhances the functionality of Virtual Private Networks by
maintaining secure connections as the mobile node moves.

Limitations of Mobile IP

1. Triangle Routing: Packets from the Correspondent Node to the mobile node
must first go through the Home Agent, leading to suboptimal routing.
2. Latency: The process of discovering a new network and registering with the
Home Agent can introduce delays.
3. Security Risks: Mobile IP introduces additional security risks that need to be
mitigated through robust authentication and encryption mechanisms.
Key Mechanisms in Mobile IP:

Tunneling: Establishes a virtual pipe (tunnel) between the home agent and the foreign agent
for packet transmission.
Route Optimization: Optimizes routing to reduce latency and improve efficiency.
Wireless Markup Language (WML)

1. What is WML?
o WML stands for Wireless Markup Language.
o It is based on XML and is specifically designed for creating content and
formatting presentations on devices that implement the Wireless Application
Protocol (WAP) specification, such as mobile phones.
o WML provides navigational support, data input, hyperlinks, text and image
presentation, and forms, much like HTML (Hypertext Markup Language) for
the web.
2. Purpose and Features:
o WML serves a similar purpose to HTML (Hypertext Markup Language)
but is optimized for mobile devices.
o Key features of WML include:
▪ Navigational Support: WML allows users to navigate through
content efficiently.
▪ Data Input: Supports input elements like password entry, option
selectors, and text entry controls.
▪ Hyperlinks: Enables linking between different pages or cards
within a WAP site.
▪ Text and Image Presentation: WML provides guidelines for
presenting text and images to users.
▪ Forms: Allows users to interact with forms on mobile devices.
3. Deck and Card Metaphor:
o WML follows a metaphor of decks and cards:
▪ A WML document is composed of multiple cards.
▪ Each card represents a page or screen displayed to the user.
▪ Users navigate through cards, similar to how they navigate
through pages in an HTML website.
4. Constraints and Considerations:
o WAP sites (built using WML) differ from normal HTML sites:
▪ Monochromatic (black and white) display.
▪ Limited screen space due to small mobile screens.
▪ Content must be concise and significant.
▪ Images should be in WBMP format (monochrome).
5. Use Cases:
o WML is commonly used for creating mobile-friendly websites,
especially in the early days of mobile internet.
o It allowed users to access essential content on their mobile devices
despite limitations.

Applications of WML

6. Early Mobile Web Browsing: WML was used to deliver web content to early mobile
devices, enabling access to news, weather, and email.
7. Mobile Services: Telecommunications providers used WML for services like account
management, mobile banking, and customer support.
8. Interactive Services: Enabled interactive services such as voting, surveys, and simple
games on mobile devices.
o
International Mobile Telecommunications 2000 (IMT-2000)

International Mobile Telecommunications-2000 (IMT-2000) is a global standard for

third-generation (3G) wireless communications defined by the International
Telecommunication Union (ITU). The vision for IMT-2000 was to create a unified
framework for mobile networks that would enable seamless global roaming and
provide enhanced services and capabilities compared to previous generations of
mobile technology.

1. Global Standardization-IMT-2000 aimed to standardize mobile communication systems

worldwide, allowing devices and networks to be compatible across different regions and
operators. This standardization was intended to foster a truly global mobile communication
network, making it easier for users to stay connected wherever they go.

2. Higher Data Rates

One of the primary objectives of IMT-2000 was to significantly increase data transmission
rates, enabling more advanced mobile services. The target data rates were:

• 144 kbps for high mobility applications (e.g., users in moving vehicles).
• 384 kbps for pedestrian and stationary users.
• 2 Mbps for indoor and low mobility environments.

These higher data rates were essential for supporting multimedia applications, video
conferencing, and high-speed internet access on mobile devices.

3. Enhanced Services

IMT-2000 was designed to support a wide range of services beyond traditional voice calls,
including:

• Multimedia Messaging Services (MMS): Sending multimedia content such as

images, audio, and video.
• Video Calls: Real-time video communication.
• Internet Access: High-speed access to the internet and web-based services.
• Mobile TV: Streaming television content to mobile devices.
• Location-Based Services: Services that use the geographic location of a device to
provide information or functionality.
4. Seamless Roaming

Another key aspect of the IMT-2000 vision was to provide seamless global roaming. This
meant that users could move between different networks and countries without losing
connectivity or needing to change their devices or numbers. IMT-2000 aimed to achieve this
through standardized protocols and interoperability between different network types.

5. Spectrum Efficiency

IMT-2000 focused on more efficient use of the available radio spectrum to support a higher
number of users and services. This was achieved through advanced technologies such as:

• Code Division Multiple Access (CDMA): A spread-spectrum technology that allows

multiple users to share the same frequency band by assigning unique codes to each
user.
• Time Division Multiple Access (TDMA): Divides each frequency into time slots,
allowing multiple users to share the same channel by using different time slots.
 • Frequency Division Multiple Access (FDMA): Allocates separate frequency bands to
different users.
• 6. Compatibility with Existing Networks
• IMT-2000 was designed to be backward compatible with existing 2G networks
such as GSM and CDMA, ensuring a smooth transition for operators and
users moving from 2G to 3G networks. This compatibility allowed users to
continue using their 2G devices and services while benefiting from the new 3G
capabilities as they became available.
•
IMT-2000 Technologies

• IMT-2000 encompasses several different technologies and standards that

meet its objectives.

1. WCDMA (Wideband Code Division Multiple Access): Used in UMTS networks,

providing high data rates and support for a wide range of services.
2. CDMA2000: An evolution of CDMA technology, offering improved performance and
compatibility with earlier CDMA systems.
3. TD-SCDMA (Time Division Synchronous Code Division Multiple Access): Developed
in China, integrating aspects of both CDMA and TDMA technologies.
4. EDGE (Enhanced Data rates for GSM Evolution): An upgrade to GSM networks,
increasing data transmission rates to support 3G services.

Impact and Benefits of IMT-2000

1. Improved User Experience: Higher data rates and enhanced services significantly
improved the user experience, enabling new applications and use cases for mobile
devices.
2. Global Connectivity: Standardization facilitated global connectivity and roaming,
making it easier for users to stay connected while traveling.
3. Economic Growth: The deployment of 3G networks spurred economic growth by
enabling new business models and services, such as mobile internet access and
mobile commerce.
4. Foundation for Future Technologies: IMT-2000 laid the groundwork for future
generations of mobile technology, including 4G (LTE) and 5G, by introducing
advanced concepts and technologies.

Challenges and Limitations

1. High Deployment Costs: Building and upgrading networks to support IMT-2000

standards required significant investment from operators.
2. Spectrum Allocation: Securing the necessary spectrum for 3G services was a
complex and often contentious process, involving coordination between
governments, regulators, and operators.
3. Device Compatibility: Ensuring that devices were compatible with the various IMT-
2000 technologies posed a challenge, particularly in the early stages of 3G
deployment.
4. Market Penetration: The adoption of 3G services varied significantly across different
regions, with some areas experiencing rapid growth while others lagged behind.
(W-CDMA)

Wideband Code Division Multiple Access (W-CDMA) is a third-generation (3G) mobile

communication technology standardized by the International Telecommunication Union
(ITU) under the IMT-2000 specifications. It is a key component of the Universal Mobile
Telecommunications System (UMTS), which is used by many mobile carriers worldwide to
provide 3G services.

1. Fundamental Concepts

W-CDMA is a type of Code Division Multiple Access (CDMA) technology that uses a wider
radio frequency band compared to earlier CDMA systems. It allows multiple users to share
the same frequency band by assigning unique spreading codes to each user, ensuring that
the signals can be separated and decoded at the receiver.

2. Technical Features
• Bandwidth: W-CDMA typically uses a 5 MHz bandwidth for each carrier, which is
significantly wider than the 1.25 MHz bandwidth used in earlier CDMA
systems.
• Spreading Codes: Unique spreading codes (orthogonal codes) are used to
distinguish between different users’ signals.
• Data Rates: W-CDMA supports high data rates, up to 2 Mbps for stationary or
slow-moving users, and lower rates for high mobility users.
• Duplexing: W-CDMA supports both Frequency Division Duplex (FDD) and
Time Division Duplex (TDD) modes, although FDD is more commonly used.
3. Architecture
• User Equipment (UE): Mobile devices such as smartphones, tablets, and data
cards.
• Node B: The base stations in W-CDMA, equivalent to BTS in GSM, responsible
for radio transmission and reception.
• Radio Network Controller (RNC): Manages radio resources, handovers, and data
transmission between Node Bs and the core network.
• Core Network: Includes elements like the Mobile Switching Center (MSC) for circuit-
switched services and the Serving GPRS Support Node (SGSN) and Gateway GPRS
Support Node (GGSN) for packet-switched services.
4. Advantages
• High Data Rates: W-CDMA supports higher data rates, enabling services like video
streaming, high-speed internet access, and multimedia messaging.
• Capacity and Efficiency: The wide bandwidth and use of spreading codes improve
capacity and spectrum efficiency, allowing more users to share the same frequency
band.
• Global Standard: W-CDMA is a globally standardized technology, ensuring
compatibility and interoperability across different regions and networks.
6. Applications
• Mobile Internet: High-speed internet access on mobile devices, enabling browsing,
streaming, and online gaming.
• Multimedia Services: Support for multimedia messaging services (MMS), video calls,
and mobile TV.
• Enterprise Applications: Mobile VPNs, remote access to corporate networks, and
other enterprise applications.
• Location-Based Services: Enhanced accuracy for GPS-based services and other
location-based applications.
CDMA2000:
CDMA2000 is a family of third-generation (3G) mobile communication standards developed
by the Telecommunications Industry Association (TIA) and standardized by the International
Telecommunication Union (ITU) under the IMT-2000 specifications. It is an evolution of the
second-generation (2G) CDMA technology (IS-95), providing higher data rates and improved
voice and data services.
1. Fundamental Concepts-W-CDMA is a type of Code Division Multiple Access (CDMA)
technology that uses a wider radio frequency band compared to earlier CDMA systems. It
allows multiple users to share the same frequency band by assigning unique spreading
codes to each user, ensuring that the signals can be separated and decoded at the receiver.
2. Technical Features
• Bandwidth: W-CDMA typically uses a 5 MHz bandwidth for each carrier, which is
significantly wider than the 1.25 MHz bandwidth used in earlier CDMA systems.
• Spreading Codes: Unique spreading codes (orthogonal codes) are used to
distinguish between different users’ signals.
• Data Rates: W-CDMA supports high data rates, up to 2 Mbps for stationary or slow-
moving users, and lower rates for high mobility users.
• Duplexing: W-CDMA supports both Frequency Division Duplex (FDD) and Time
Division Duplex (TDD) modes, although FDD is more commonly used.
4. Architecture
The W-CDMA architecture consists of several key components:
• User Equipment (UE): Mobile devices such as smartphones, tablets, and data cards.
• Node B: The base stations in W-CDMA, equivalent to BTS in GSM, responsible for
radio transmission and reception.
• Radio Network Controller (RNC): Manages radio resources, handovers, and data
transmission between Node Bs and the core network.
• Core Network: Includes elements like the Mobile Switching Center (MSC) for circuit-
switched services and the Serving GPRS Support Node (SGSN) and Gateway GPRS
Support Node (GGSN) for packet-switched services.
4. Advantages
• High Data Rates: W-CDMA supports higher data rates, enabling services like video
streaming, high-speed internet access, and multimedia messaging.
• Capacity and Efficiency: The wide bandwidth and use of spreading codes improve
capacity and spectrum efficiency, allowing more users to share the same frequency
band.
• Global Standard: W-CDMA is a globally standardized technology, ensuring
compatibility and interoperability across different regions and networks.
• Quality of Service (QoS): W-CDMA supports various QoS classes, ensuring different
levels of service quality for different applications, such as voice, video, and data.
5. Challenges
• Complexity: The technology and network infrastructure required for W-CDMA are
more complex than earlier systems, leading to higher deployment and maintenance
costs.
• Power Consumption: W-CDMA devices tend to consume more power, impacting
battery life compared to earlier technologies.
• Interference Management: The wideband nature of W-CDMA requires effective
interference management to maintain signal quality and network performance.
6. Applications
• Mobile Internet: High-speed internet access on mobile devices, enabling browsing,
streaming, and online gaming.
• Multimedia Services: Support for multimedia messaging services (MMS), video calls,
and mobile TV.
• Enterprise Applications: Mobile VPNs, remote access to corporate networks, and
other enterprise applications.
• Location-Based Services: Enhanced accuracy for GPS-based services and other
location-based applications.
Wireless Local Loop (WLL)
The Wireless Local Loop (WLL) architecture replaces traditional copper wires with wireless
links, connecting subscribers to the local central office. It offers an alternative to the
conventional wired local loop, especially in rural or remote areas where installing copper
wires is risky and costly due to fewer users. Here are the key components and features of
WLL:
1. Components:
o PSTN (Public Switched Telephone Network): The PSTN serves as a circuit-
switched network, connecting subscribers to the telephone system.
o Switch Function: The switch function manages connections between
Wireless Access Network Units (WANUs).
o WANU (Wireless Access Network Unit): The WANU is located at the local
exchange office. All local Wireless Access Subscriber Units (WASUs) are
connected to it. Its functions include authentication, operation, routing, and
data transmission.
o WASU (Wireless Access Subscriber Unit): The WASU is installed at the
subscriber’s location (e.g., home). It connects the subscriber to the WANU,
providing wireless access.
2. Advantages of WLL:
o Elimination of First Mile Construction: WLL eliminates the need for
constructing the first mile (or last mile) of network connections using
conventional copper wires.
o Cost-Effectiveness: WLL is cost-effective because it avoids the use of
expensive copper wires.
o Enhanced Security: WLL uses digital encryption techniques in wireless
communication, making it more secure.
o Scalability: WLL is highly scalable as it doesn’t require additional wire
installations for expansion.
3. Features of WLL:
o Internet Connection via Modem: WLL provides internet connectivity via
modems.
o Data Services: It supports data services for subscribers.
o Voice Services: WLL enables voice communication.
o Fax Services: Subscribers can send and receive faxes.
4. WLL Network Architecture
Access Network
• Subscriber Units (SUs): These can be fixed wireless terminals or mobile
handsets that connect to the base station via wireless links.
• Base Stations (BS): Serve as the central communication point for multiple
subscriber units. They transmit and receive radio signals and connect
subscribers to the core network.
Transmission Network
• Microwave Links: Used for backhaul connections between base stations and
the switching center when physical cabling is not feasible.
• Fiber Optic Links: Provide high-capacity, low-latency connections where
available.
Core Network
• Switching Center: Handles call setup, routing, and termination, connecting the
WLL system to external networks.
• Network Management Systems: Monitor and control the operation of the WLL
network, ensuring reliability and performance.
WLAN

Wireless Local Area Network (WLAN) technology enables devices to connect to a

network wirelessly within a limited area, typically a few hundred feet. In mobile
computing, WLANs provide flexibility and mobility, allowing users to access network
resources and the internet without being tethered to a physical connection. WLANs
are widely deployed in various environments, including homes, offices, public spaces,
and enterprise settings, offering high-speed connectivity for laptops, smartphones,
tablets, and other mobile devices.

WLAN Architecture

1. Infrastructure Mode: In this mode, wireless clients connect to a central

access point, which manages network access and communication. This
mode is commonly used in enterprise and public WLAN deployments.
2. Ad-hoc Mode: Also known as peer-to-peer mode, this mode allows devices to
connect directly to each other without the need for a central access point. Ad-
hoc networks are typically used for temporary or ad-hoc connections, such as
file sharing between devices.

Advantages of WLAN in Mobile Computing

1. Mobility: Users can move freely within the coverage area of the WLAN without
losing network connectivity, enhancing productivity and convenience.
2. Flexibility: WLANs can be deployed quickly and easily, making them suitable
for temporary or dynamic environments such as conferences, events, and
outdoor spaces.
3. Scalability: WLANs can scale to support a large number of users and devices,
making them suitable for both small-scale and enterprise deployments.
4. Cost-Effective: Compared to wired networks, WLANs can reduce installation
and maintenance costs, especially in environments where wiring is
impractical or expensive.
5. High-Speed Connectivity: Modern WLAN standards offer high data rates,
enabling fast internet access and seamless multimedia streaming on mobile
devices.

Applications of WLAN in Mobile Computing

1. Business and Enterprise Networks: WLANs are widely used in office

buildings, campuses, and other enterprise environments to provide employees
with wireless connectivity for accessing corporate resources, email, and
internet.
2. Public Wi-Fi Hotspots: WLANs are deployed in public spaces such as airports,
coffee shops, hotels, and libraries to offer internet access to visitors and
customers.
3. Smart Homes and IoT: WLANs play a key role in connecting smart home
devices and IoT (Internet of Things) devices, allowing users to control and
monitor their home appliances, security systems, and other IoT devices
remotely.
4. Education and Healthcare: WLANs are deployed in schools, universities,
hospitals, and healthcare facilities to support mobile learning, telemedicine,
and electronic health records (EHR) systems.