(QP4) Elaborately describe the different technologies and interfaces used in wireless
communication(5)
Wireless/Mobile Computing Technologies
Here are the list of some important technologies and interfaces used for wireless and mobile
computing that you will learn in separate tutorials:
GSM
CDMA
WLL
GPRS
1G, 2G, 3G, and 4G Networks
3G and EDGE
4G and LTE
SMS
Chat
Video Conferencing
Voice over Internet Protocol (VoIP)
Wi-Fi
Wi-Fi Hotspots
WiMax
(QP6) List out the limitations of Mobile Computing(5)
Limitations of Mobile Computing
Resource constraints: Battery
Interference: Radio transmission cannot be protected against interference using
shielding and result in higher loss rates for transmitted data or higher bit error rates
respectively
Bandwidth: Although they are continuously increasing, transmission rates are still
very low for wireless devices compared to desktop systems. Researchers look for
more efficient communication protocols with low overhead.
Dynamic changes in communication environment: variations in signal power within a
region, thus link delays and connection losses
Network Issues: discovery of the connection-service to destination and connection
stability
Interoperability issues: the varying protocol standards
Security constraints: Not only can portable devices be stolen more easily, but the
radio interface is also prone to the dangers of eavesdropping. Wireless access must
always include encryption, authentication, and other security mechanisms that must
be efficient and simple to use.
(QP6) Examine the simplified reference model in which the protocol stack
has been implemented in the system.(10)
A simplified reference model
The figure shows the protocol stack implemented in the system according to the
reference model. End-systems, such as the PDA and computer in the example, need a full
protocol stack comprising the application layer, transport layer, network layer, data link
layer, and physical layer. Applications on the end-systems communicate with each other
using the lower layer services. Intermediate systems, such as the interworking unit, do not
necessarily need all of the layers.
A Simplified Reference Model
The figure shows the protocol stack implemented in the system according to the
reference model. End-systems, such as the PDA and computer in the example, need a full
protocol stack comprising the application layer, transport layer, network layer, data link
layer, and physical layer. Applications on the end-systems communicate with each other
using the lower layer services. Intermediate systems, such as the interworking unit, do not
necessarily need all of the layers.
● Physical layer: This is the lowest layer in a communication system and is responsible for
the conversion of a stream of bits into signals that can be transmitted on the sender side. The
physical layer of the receiver then transforms the signals back into a bit stream. For wireless
communication, the physical layer is responsible for frequency selection, generation of the
carrier frequency, signal detection (although heavy interference may disturb the signal),
modulation of data onto a carrier frequency and (depending on the transmission scheme)
encryption.
● Data link layer: The main tasks of this layer include accessing the medium, multiplexing
of different data streams, correction of transmission errors, and synchronization (i.e.,
detection of a data frame). Altogether, the data link layer is responsible for a reliable pointto-
point connection between two devices or a point-to-multipoint connection between one
sender and several receivers.
● Network layer: This third layer is responsible for routing packets through a network or
establishing a connection between two entities over many other intermediate systems.
Important functions are addressing, routing, device location, and handover between different
networks.
● Transport layer: This layer is used in the reference model to establish an end-to-end
connection
● Application layer: Finally, the applications (complemented by additional layers that can
support applications) are situated on top of all transmission oriented layers. Functions are
service location, support for multimedia applications, adaptive applications that can handle
the large variations in transmission characteristics, and wireless access to the world-wide
web using a portable device.
GSM : Computer Definition (Global System for Mobile Communications) A digital
cellular phone technology based on TDMA that started in Europe and migrated to other
continents. ... The SIM Card GSM phones use a Subscriber Identity Module (SIM) smart
card that contains user account information.
GPRS : General Packet Radio Services (GPRS) is a packet-based wireless
communication service that promises data rates from 56 up to 114 Kbps and continuous
connection to the Internet for mobile phone and computer users. GPRS is based on
Global System for Mobile (GSM) communication
(QP7) Identify the GSM network elements inside a GPRS network and
how is it being used in GPRS? In what way it reduces the infrastructure
capital investments.(5)
GSM network elements inside a GPRS network and how is it being used in GPRS?
In what way it reduces the infrastructure capital investments
GSM Network Element Modification or Upgrade Required for GPRS.
Mobile Station (MS) New Mobile Station is required to access GPRS services. These
new terminals will be backward compatible with GSM for voice
calls.
BTS A software upgrade is required in the existing Base Transceiver
Station(BTS).
BSC The Base Station Controller (BSC) requires a software upgrade and
the installation of new hardware called the packet control unit
(PCU). The PCU directs the data traffic to the GPRS network and
can be a separate hardware element associated with the BSC.
GPRS Support Nodes (GSNs) The deployment of GPRS requires the installation of new core
network elements called the serving GPRS support node (SGSN)
and gateway GPRS support node (GGSN).
Databases (HLR, VLR, etc.) All the databases involved in the network will require software
upgrades to handle the new call models and functions introduced by
GPRS.
(QP9,10)
Differentiate between Fixed network and Wireless
Network. Which one is better and why?
Describe about mobile communication types in wireless
networks.
Refer unit 1
DIFFERENCE BETWEEN CDMA AND GSM
Comparison Chart
BASIS FOR
GSM CDMA
COMPARISON
Basic GSM is SIM specific. CDMA is Handset specific.
Full Form Global System for Mobile Code Division Multiple Acess.
communication.
Technology FDMA and TDMA CDMA
Network Network Tower in each cell There are a physical channel and a
serves the mobile phone of that dedicated code for each device in the
area. network.
Transmission Voice and data transmission at Cannot do voice and data
the same time. transmission simultaneously.
BASIS FOR
GSM CDMA
COMPARISON
Roaming Worldwide. Limited.
Data Rate Slower. Faster.
