Mobile Computing

MOBILE COMPUTING
(IV –I B.Tech R10 Regulation)
AMRITA SAI INSTITUTE OF SCIENCE & TECHNOLOGY
RAMESH BABU PALEPU
Associate Professor

UNIT-I
• An overview of mobile communication
• Guided Transmission
• Unguided Transmission
• Signal propagation frequencies
• Antennae
• Modulation
• Modulation methods & standards for voice
oriented data communication standards
• Modulation methods & standards for data
and voice oriented data communication
standards

• Mobile computing –Novel applications &
limitations
• Mobile computing architecture
• Mobile system networks
------------------------------------------------------
-
What is a network?
Let me allow different kinds of networks
before we start our actual discussion. It is
possible to classify the net works on
various parameters, such as i)
Geographical area ii) According to the
topology iii) According to the protocols

iv) According to the data transmission v)
According to the routing vi) According to
the physical media etc..
Now we discuss about mobility- Today the
most of the computing devices are portable
that is we can easily carry the devices from
one place to another place.
The characteristic of device portability leads
to the mobility. It means ability to move.
The mobile computing means ‘the
computing systems that may easily moved
while they are being perform some
task’(computation)

There are two kinds of mobility’s.
a)User mobility - In user mobility a user can
access the same or similar services at
different places. That is the user can be
mobile, and services will follow him.
b)Device mobility - the communication
device moves with or without help of a
user. Several techniques in
communication network guarantees that
communication is even possible while
device is being moved.

• The following are the four different
characteristics exhibit by the
communication devices.
A) Fixed and wired: This category describes
the fixed desktop computers in the office,
which are connected through the wired
network. The weight and power
consumption of these devices does not
permit for mobility, these devices use fixed
network for information accessing

B) Mobile and wired: The most of the
portable computing devices fall within this
category. We      can easily carry these
devices (eg: laptops) from one place to
another place and      reconnecting to the
organization’s network via the telephone
lines or a modem.
C) Fixed and wireless: This kind of technique
is especially used for installing networks in
     historical places such as buildings to
avoid damages by fixing cables and other
equipment.      This method can also be
used for fastest network setup.

D) Mobile and wireless: This is the most
recent technique, in which no cable
restricts, the user, who can roam
between different wireless networks.
Eg:GSM –Global system for mobile
communications.
Limitations of MC:
1.Power consumption
2.Tiny Keypads
3.Small Displays

Applications of MC
1.Vehicles
2.Emergencies
3.Business
4.Replacement of Wired networks
5.Infotainment.
6.Location dependent services.
a) Follow on services
b) Location aware services
c) Privacy
d) Information services

MOBILE COMMUNICATION
• Communication is a two transmission and
reception of data, voice, or multimedia
content through a fiber, wire, or wireless
medium.
• The transmission takes place by
generating the signals according to defined
regulations, standards and protocols.
• Here the signal can be defined as variation
of voltage ‘v’ or current ‘i’ between two
points in a circuit. The values of v or i
change as function of time t.

• The signal frequency is defined as signal
voltage v or current i oscillates 109
times
between maximum and minimum values
then the electrical signal frequency f=109
Hz (1 GHz).
• The simplest representation of the signal
(s) in the form of sinusoidal function of
time, here the changes in the amplitudes
of signal are represented by s(t) which
varies sin of an angle between 0 to 360.
• S(t) = S0 sin [(2π x f x t) + θt0

Guided Transmission
• Metal wires and optical fibers are used in
guided or wired transmission of data. The
guided transmission takes place using four
types of cables.
i) Optical fibers for signals of wavelength
1.35 – 1.5 µm.
ii) coaxial cable for electrical signals of
frequency up to 500 MHz to a range of 40
m.
iii) Twisted pairs for electrical signals of up
to 100 MHz to a range of 2 Km

iv) Power lines are used for long
transmission of frequencies between
10KHz to 522 KHz.
Advantages:
• Transmission is along a directed path from
one point to another.
• Practically there is no interference of
external sources.
• A large number of sources can
simultaneously transmitted along optical
fiber, coaxial, or twisted pair by using
multiplexing and coding techniques.

Disadvantages:
• In guided transmission transmitting and
receiving points are fixed.
• The total number of interconnections
between transmitters and receivers are
limited.
UNGUIDED TRANSMISSION
• Unguided transmission or wireless
transmission is carried out through
radiated electromagnetic energy. Here the
electromagnetic energy flows in free space
in the form of MHz or GHz spectrum rage.

• Here the spectrum means the set of
frequencies.
Signal Propagation Frequencies:
• Generally electrical signals are converted
into electromagnetic radiation and then
transmitted through antennae.
• There are various frequency bands in
electromagnetic spectrum and each of one
have different transmission requirements.
• The electromagnetic signal frequency in
vacuum or air is defined as;
f = c/λ = (300/ λ)MHz [λ in meter]

• Here f in MHz and wavelength λ in meters
and c is the velocity of signal propagation,
it is 3 x106
m/s.
• The following table illustrate some wireless
transmission frequencies and their
properties;

The following are some of the signal
propagation frequencies and their
wavelengths;
1.Long wavelength radio, very low frequency
(LW):30KHz to 1 MHz wavelength in
10,000 to 300 meters.
2.Medium wavelength radio, Medium
frequency (MW):0.5 to 2 MHz and
wavelength in 600 to 150 meters.
3.Short wavelength radio, high frequency
(SW): 6 to 30MHz and wavelength in 50to
10 meters.

4. FM radio: 87.5 to 108 MHz and 3.4 to 2.8
meters wavelength then operated in 50km
range.
5. VHF: 50 to 250 MHz and wavelength in 6
to 1.2 meters.
6. UHF: 200 to 2000 MHz and wavelength in
1.5 to0.15 meters
7. Super High Microwave Frequency: 2 to 40
GHz and wavelength in 15 to 0.75 cm.
8.Extreme High Frequency(EHF): operated
above 40 GHz and wavelength in 0.75cm
to 3μm.

9. Far infrared: (1.5 to 3)x 1014
Hz and
wavelength between 1.0 μm to 2.0 μm.
10. Infrared: 0.70 to 0.40 μm wavelength
and operated (3.3 to 3.5)x 1014
Hz.
ANTENNAE
• Antennae are devices that transmit and
receive electromagnetic radiations most
function efficiently for relatively narrow
frequency ranges.
• If not properly tuned to the frequency band
in which the transmitting system
connected to it operates, the transmitted
or received signals may be impaired.

• The forms of antennae are chiefly
determined by the frequency ranges they
operate in and can vary from a single piece
of wire to a parabolic dish.
• The following diagram shows λ/2 Dipole
Antenna for wireless transmission of waves
of wavelength λ.

• It is called dipole antenna because at any
given instant at both the ends the signals
are1800 out of phase.
• The following diagram shows another
antenna of length λ/4 mounted on a long
conducting surface.

• One of the important characteristic of
antenna is radiation pattern which defines
a path on which each point will have
identical signal strength at any given
instant t.
• The radiation pattern is two types i)
Circular pattern ii) Directed pattern.
• The following diagram shows radiation
pattern of λ/2 dipole antenna in z-y and x-
z planes. It indicates signal amplitude at
an instant is identical along the circles and
antenna axis is perpendicular to the plane
of circles and tangent to both circles.

• The following diagram shows radiation
patterns of λ/4 dipole antenna in y-z and
x-z planes.
• In circular radiation pattern the radiated
energy and signal strength is equally
distributed in all directions in the plane.
• A pattern in which the signal strength is
directed along a specific direction is called

Antenna For Multiple Input Multiple Output
(MIMO):
• To explain MIMO let us consider two
sources which are physically separated by
a distance and assume one emitting red
light and other emitting green light, but
both incident on the same point (reach
same destination).
• We know that the color appears at the
incident point will be different from the
color of any one of the source, because the
beams are travel on different paths and
phase angle also different, which depends

On time and distance travelled by the
beams.
• The end resultant color determined by the
distance between the sources and phase
difference the source signals.
• Generally the resultant color has
maximum intensity than the two source
signals.
• The MIMO technology use more then one
antenna which was physically separated
and multiple antenna outputs are used for
transmission. So the resultant output is
different from each antenna output.

• So it is possible in MIMO two or more
sources’ signals can travel on different
paths, and their frequencies and phase
angles are carefully selected at receiver
ends.
• In MIMO one antenna radiating (sending)
signal in receiver direction is placed in the
vicinity of another antenna radiating in the
same direction.
• Appropriate separation between antennas
cause constructive interference between
radiations from them.

• Now the receiver got the superimposed
signal which causes increase wireless link
range. This phenomena is used to code the
signals and increase the transmitted
spectral efficiency.
• In MIMO multiple antennae can be used
for wireless communication. Assume ‘n’
antennae has separated at transmitter
side, here the distance between antennae
is significantly large.
• Now multiple wavelengths can generated
at transmitted station which causes
multiple outputs.

• These multiple outputs can thus received
at receiving station using multiple
antennae as a inputs to receiver.
• Here the receiver may have 1 or ‘m’
separated antennae. The space between
the receiver antennae is small.
• Now each receiver able to receive ‘n’
signals transmitted through ‘n’ paths. So
the signal propagates through a matrix of
‘n x m’ paths this is called MIMO.

Propagation of signals
• The wireless communication requires
reliable transmission, but it is difficult
wireless transmission rather than fixed
wired communication because the wireless
transmission may face many
complications.
• we know that now a days the antennae
size and height is very small so the
obstacles in the vicinity of antennae
certainly influence the propagation of
signals.

• We know that the propagation properties
may depend on the time, place and
weather and soon.
• To minimize the impairing effects, the
signal propagation routes are designed and
calculated by considering the various
propagation losses.
• The following things should consider
during the propagation of the signal;
a) Line of sight: It is the transmission of the
signal without refraction, diffraction and
scattering, even though transmission
losses may occur.

• We know that the strength of the signal
decreases as the square of the distance
from the transmitter. This is due to
radiated power is distributed over a large
spherical surface.
b) The signal strength may also decreases
due to attenuation. Suppose the obstacles
in the path of signal is greater in size than
the wavelength of the signal then
attenuation of signal happens.
• For example:
FM band signal transmitter 90 MHz (λ =3.3 m) faces─
attenuation of in objects of size 10 m and above

GSM 900 MHz (λ > = 33 cm) signal then it will face
attenuation in objects of size > 1 m (>> λ ~ 33 cm)
c) The signal scatters when it encounters an
obstacle of size equal or less than the
wavelength of the signal. For example GSM
signal, about 33 cm in wavelength,
scattered by an object of 30 cm or less.
d) The signal bends as the result of
diffraction from the edges of an obstacle of
size equal to or less than the wavelength.
For example GSM signal of wavelength 33
cm will diffract from an object of 33 cm or
less.

• The diffracted signal may or may not reach
the destination. It depends upon geometry
of the obstacle and separation between the
transmitter and receiver. The following
diagram shows diffraction of signal.
e) Signal reflected from the surface of an
obstacle, whose size is greater than the
wavelength of the signal.

• For example GSM 900 MHz (λ = 33 cm)
signal the transmitter signal reflects from
an object of size 10 m and above (much
greater than λ). The following diagram
shows the reflection of signal.
• The reflected signal may undergoes the
transmission delay, the delay is the
common phenomena in multi hop path.

• The delayed signals have distorted wave
forms and cause misrepresentation of
information encoded in the signal.
• We use digital signaling processing to
avoid distortion caused by delays. The
delay in reflected signal with respect to the
original direct signal is given as,
tindirect - tdirect = additional path travel in meters
3 x 108
ms-1

Modulation Methods & Standards for Voice
Oriented Data
• First generation wireless devices communicated
only voice signals the symbol 1G refers voice only.
• Second generation (2G) devices communicate voice
as well as data, it is introduced in 1988, the 2G
signals have transmit the data rates of up to 14.4
kbps.
• The 2.5G and 2.5G+ are enhancements of the
second generation and sport data rates up to 100
kbps.

• The 3G supports Higher data rates than 2G and
support voice, data, and multimedia streams.
• The 3G supports data rates of 2 Mbps or Higher for
short distances and 384 kbps for long distance
transmissions.
• High data rates in 3G Enable transfer of video clips
and faster multimedia communication.
• 4G supports the higher data rates than 3G it
facilitates streaming data for video and enables
multimedia news paper, high resolution mobile TV,
IP telephony and data rates up to 100 Mbps.

• GSM Standard: To day the most successful digital
mobile telecommunication system is G.S.M. its
original name is “Groupe speciale mobile” was
founded in 1982.
• Its name soon changed as “Global system for
mobile communications”, with specification of
procedures designed by European
Telecommunications standards Institute (ETSI) after
that the universal mobile Telecommunication
systems (UMTS) add new standards to G.S.M.
• The GSM standard for mobile telecommunication
through a cellular network at data rates of up to
14.4kbps and uses time-slices of 577 μs.

• GSM 900 standard was founded in 1988 by GSM
which uses GMSK (Gaussian Minimum Shift Keying)
modulation for transmitting 1s and 0s.
• The primary goal of G.S.M was to provide a mobile
phone system that allows users to roam seamlessly
and provide voice services compatible to ISDN and
PSTN systems.
• There are several versions in GSM depending on
various standards and different uplink and downlink
frequencies.

• GSM 900-it is initial version of GSM developed in
Europe using 890-915 MHz uplink and 935-960mhz
down link frequency.
• DCS 1800-digital cellular system is a version of GSM
using 1710-1785 MHz up link and 1805-1880 MHz
down link frequencies.
• PCS 1900- personal communication service is a
version of GSM using 1850-1910 MHz uplink and
1930-1990 MHz down link frequencies.

• GSM-R (Rail)-this version of GSM offers many
additional services which are un-available with
public GSM. It offers 19 channels for voice and data
traffic .other services are, emergency calls with
acknowledgement, voice group call service, voice
broadcast service etc.
• EGSM: Extended GSM provides an additional
spectrum of 10 MHz on both uplink and down link
channels. So the operating frequency of EGSM is
880-915 MHz uplink and 925-960 MHz downlink.
The additional 10 MHz on each side provides an
additional 50 channels of 200 KHz each.

• EGSM communication frequency spectrum lies in
three bands 900/1800/1900 MHz. this is therefore
known as tri-band.
GPRS [GSM Phase 2+ (2.5G)]: General Packet Radio
Service is a packet oriented service for data
communication of mobile devices and utilizes the
unused channels in TDMA mode in GSM network.

EDGE (Enhanced Data rates for GSM Evolution): It is a
enhancement of GSM phase 2. it uses PSK
modulation for communication for higher rates up
to 48kbps per 200 kHz channel. EGPRS (Enhanced
GPRS): It is an extension of GPRS using PSK
modulation. It enhances the data communication
rates based on EDGE and uses High Speed Circuit
Switched Data (HSCSD).

Modulation Methods & Standards for Data and Voice
Communication
• Here we describe CDMA based modulation
methods and standards for mobile communication
network used for long distance communication.
• In addition to GSM, CDMA is the most popular
mobile communication standard the initial version
of CDMA was 2.5G and most famous CDMA
standard is CDMA One (IS-95).

• Cdmaone founded in 1991 by QUALCOM, USA. It
operates at 824-849 MHz and transmit analog signal
from multiple sources.The following are some of
the 3G standards based on CDMA;
3G Partnership Project (3GPP/WCDMA): It is also
known as Wide CDMA. It supports asynchronous
operations and has a 10ms frame length with 15
slices.
• Each frame both uplink and downlink modulated by
QPSK technique and uses Direct sequence of CDMA.

3GPP2: It is a 3G partnership project 2 started in
2001. it is compatible with CDMA 2000 and CDMA
2000 1x chipping rates.
• it is mainly used for voice communication, it can
transmit circuit switched as well as packet switched
techniques.
• It supports high data rates and synchronous
operations.

Universal Mobile Telecommunication System
(UMTS):
–It supports both 3GPP and 3GPP2 and transmit
the data at the rate 100kbps to2 Mbps.
–It combines several technologies for
transmission, security and management
functions.

MOBILE COMPUTING
• Mobile computing 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 synchronize
through mobile communication protocols.
• Mobile computing 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.
• Ubiquitous computing refers to the blending of
computing devices with environmental objects.
• A term that describes integration of computers into
practically all objects in our everyday environment,
endowing them with computing abilities.
• Ubiquitous computing is based on pervasive
computing.

• Pervasive means ‘existing in all parts of a place or
thing’.
• Pervasive computing is the next generation of
computing which takes into account the
environment in which information and
communication technology is used everywhere, by
everyone, and at all times.
• Pervasive computing Assumes information and
communication technology to be an integrated part
of all facets of our environment, such as toys,
computers, cars, homes, factories, and work-areas.

• Mobile computing Also called pervasive computing
when a set of computing devices, systems, or
networks have the characteristics of transparency,
application-aware adaptation, and have an
environment sensing ability.
Limitations of mobile computing:1.
1. Resource constraints – Battery needs and recharge
requirements are the biggest constraints of mobile
computing.
2.Interference – there may be interference in wireless
signals affecting the quality of service.

3. Bandwidth – there may be bandwidth constraints
due to limited spectrum availability at given instant
causing connection latency.
4. Dynamic changes in communication environment -
We know that there may be variations in signal
power within a region it causes link delays and
connection losses.
5. Network issues – Due to the ad hoc networks some
issues relating discovery of connection, service to
destination, and connection stability.

6. Interoperability – The varying protocol standards
available between different regions may lead to
interoperability issues.
7. Security constraints – Protocols conserving privacy
of communication may be violated. Some times
physical damage or loss of mobile device is
probable than static computing system.

MOBILE COMPUTING ARCHITECTURE
• Here we discuss the architecture requirements
for programming mobile device. This will
provide an overview of programming language
used for mobile software.

• We also discuss mobile OS required to run software
components on the hardware and OS functions.
• We represent the middleware components used in
the mobile devices and layered structure of mobile
computing components.
Programming languages: A variety of programming
languages are used for mobile application
development in mobile computing.

• One popular programming language is Java,
because of platform independent, the code
developed in java independent of CPU and OS of
the system.
• J2SE-Java 2 standard Edition and its two versions of
J2ME-Java 2 Micro Edition and Java card and J2EE-
Java 2 Enterprise Edition used for developing
mobile applications.

Functions of OS: We know that an OS enables user
to run applications without knowing hardware
specifications and functionalities.
• The mobile OS provides functions for scheduling
multiple tasks, memory management tasks,
synchronization and priority allocation.
• The mobile OS also provides interfaces for
communication between application layers,
middle ware layers and hardware.

• The mobile OS provides configurable libraries for
GUI in the device and phone API, it also provides
new application development environment.
Functions of middleware: Middleware are the
software components that link application
components with network distributed components,
mobile OS provides middleware components.

• The following are some middleware applications;
1. Discover the nearby Bluetooth device.
2. Discover nearby hotspot.
3. Achieve device synchronization with server or an
enterprise server.
4. Retrieve data from network database.
1.Adaptation of application to the platform and
service availability.
Mobile computing architectural layers: Mobile computing
architecture refers to define various layers between user
applications interfaces, devices and network hardware.

• A well defined architecture is required for
systematic computations and access data and
software objects.
• The following diagram shows mobile computing
architecture for mobile device.

• Here two adjacent layers interact with each other
and other with the help of input-output interface.
• All mobile APIs are appear at application layer and
components in middleware layer discover the
service, link the client and network service, update
database, manage the devices using remote server
software, perform client server synchronzation and
soon.
Protocols: Generally to perform interchanges between two
diversified and distributed components need protocols and
standards.

• Mobile computing use number of protocols such as
GSM 900/1800/1900, CDMA, WCDMA, HSPA,
UMTS, i-Mode, LTE and WiMax.
• Layers There are different layers in network
transmission and reception or interchange of
information. The following are some layers in
Mobile computing as per OSI model.1.Physical layer
– Sending and receiving signals
• Data link layer – multiplexing
• Network layer – Linking to destination

5.Wireless transport layer - for establish end-to-end
connectivity.
6. Wireless transport protocol
7. Wireless session protocol
8. Wireless application environment
MOBILE SYSTEM NETWORKS
• Mobile network means network for mobile
devices, it consists of mobile devices,
servers, and distributed computing
systems.

• There are three types of mobile networks;
a) Cellular networks
b) Wireless LAN networks
c) Ad hoc networks
Cellular networks: A cell is the coverage
area of a base station, connected to other
stations via wire or fiber or wirelessly
through switching centers.
• The coverage area defines a cell and its
boundaries.

• Each cell base station functions as an
access point for the mobile service.
• Each mobile device connects to the base
station of the cell which covers the current
location of the device.
• All the mobile devices within the range of a
given base station communicate with each
other through that base station only.

• The following diagram shows the cellular
network;

WLAN network & Mobile IP: Mobile devices
like pocket computers and laptops
connects to an access point. The access
point, in turn, connects to a host LAN
which links up to the Internet through a
router.
• This connectivity is established between
internet, two LANs, mobile devices, and
computers.
• The following diagram shows
communication between WLAN

• Mobile IP is an open standard defined by
Internet Engineering Task Force (IETF).
• It is based on Internet Protocol (IP), all the
communication system support IP also
support mobile IP.

Ad hoc networks: In ad hoc networks the
base stations function as gateways and The
nodes, mobile nodes, and sensor nodes
communicate among themselves using a
base station.
•The ad hoc networks deployed for routing,
target detection, service discovery, and other
needs in a mobile environment.
END OF UNIT-I

UNIT-II
MOBILE DEVICES & SYSTEMS
Cellular Networks & Frequency Reuse:
• We know that mobile communication is
mostly cellular based.
• A cell is defined as a coverage of base
station, i.e. each cell as a base station and
each base station works as a access point
for the mobile devices.
• A mobile device within the cell wirelessly
communicates with base station and other
mobile devices within the cell.

• The base stations are interconnected either
wired or wirelessly form the cellular
networks.
• In cellular network neighbouring cell uses
different frequency bands in GSM
communication technology. The
frequencies are reused in nest to nest
cells.

Cellular Networks & Mobile Smart phones:
• In the above diagram a mobile service
region is divided into cells, the size of the
cell is depend on the technology and
frequency used within the cell. For
example CDMA 950 MHz cell radius is 24
km.
• Generally all the cells in the hexagonal
shape whose base stations are at the
middle and these base stations are
compatible with ISDN or PSTN.

• A multi cellular network lead to when a
mobile unit moves from one place to
another place the communication
(connection) also switched from cell to cell,
using handover technique.
• There are so many handover techniques,
due to the handover mobile unit transition
completed without disrupting ongoing
communication.
•

Frequency reuse in networks:
• We know that each cell in the network is
surrounded by cells in all directions. So
same frequency may used at all base
stations may cause the interference, then
adjacent cell may use different frequencies.
• The FDMA technique species that there
may be at least one cell gap between the
cells which reuse the same frequency.
• For example If cell A0 is using frequency
f0, then the cells A1, A2, A3 , A4, A5 and
A6 must use different frequencies.

• Assume that cell A0 is using frequency f0
then cell A1 uses f1, cell A2 uses f2 and
cell A3 can reuse f1.
• This is because A1 and A3 are not
adjacent and there is a gap of one cell
between them. Cell A4 reuses f2, cell A5
reuses f1 and cell A6 can reuse f2.
• Three separate frequencies f0, f1 and f2
are required in case frequencies are
reused. Frequency reuse factor is 1/3.

• The frequency reuse factor(u) can be 1/3,
1/4, 1/7, 1/9 and 1/12. the cell size can
also be reduced when more frequencies are
available.
• The formula for frequency reuse distance
d = r√(3xn where r is distance between cell
centre and cell boundary and n is number
of surrounding cells.
• We observe that each cell is divided into
sectors with each sector lying in different
direction from the base station.

• Assume base station use m antennas may
form m sectors. Each antennae in different
direction and use the same frequency.
Here space division multiplexing technique
is used, and here frequency reusing factor
is m/u.
• For example GSM uses a reuse pattern
3/4 and consider total bandwidth to GSM
service is ‘b’ then the number of frequency
channels that can be used =b/u.
• Each sector in GSM using SDMA can use
the bandwidth bs= b/m x u.

Capacity enhancement in networks:
Capacity enhancement takes place due to
the followings:
1.Frequency reuse: Capacity enhancement
due to frequency reuse = k × m× u. Here k
is the enhancement due to multiplexing, m
is number of sectors formed in a cell and u
is number of adjacent cells.
2.Multiplexing is also enhances the capacity.
Different channels, users, or sources can
share a common space, time, frequency, or
code for transmitting data

3. A sector antenna can be divided into
micro-sectors and each sector is along a
specific beam transmitted by the antenna.
Window Switched beam Smart antennae
use can further enhance the capacity. An
antenna can radiate p beams in different
directions. Capacity enhancement due to
frequency reuse = p × k × m× u.

MOBILE SMART PHONES, SMART MOBILES & SYSTEMS
• Mobile phones are now smart phones
which Communicate with other phones
using a cellular service-provider network
• Packed with smart functions and are
available in smaller sizes
• Applications of mobile phones no longer
confined to telephonic communication.
• Now a days mobile can synchronize and
upload and download data to and from
PCs.
• mobile smart phones provides e-mail and
Internet connectivity.

• it can send files, click pictures and prepare
albums.
•Includes a personal information manager
(PIM), a handheld computer, and an
entertainment device.
Smart phone Features:
1. A GSM, CDMA, or tri-band wireless radio
interface to a cellular network provided by a
mobile service provider.
2. Small area LCD display.
3. A smart T9 keypad─ A smart keypad is
one that remembers previously keyed
entries.

4. T9 stands for ‘text on 9 keys’.
5. A text input system that offers an
alternative to multi-tapping for entering
textual characters on a numeric keypad.
6. Smart T9 keypads useful for creating SMS
messages and entering contact information.
7. Functions as a phone as well as a PIM ─
phone diary, address book, task-list,
calculator, alarm, and calendar.
8. Ability to send and receive SMS messages
of up to 160 characters.

9. Ability to send and receive MMS (multi
media messaging service) messages for
transmission of digital images, video clips,
and animations.
10.Provisions for games, e-commerce, and
e-ticketing.
11.Bluetooth communication with PCs and
neighboring devices.
12.Integration of location information, GPS
and maps.

Multimedia features in smart phones:
• A smart phone also offers multimedia
functionalities. play MP3 format audio and
MP4 format video files
• Some phones may also support other
formats such as WMA, AAC, etc.
• many smart phones with multimedia
features include cameras for still pictures
and video recording.
• Some phones are with multimedia features
include cameras for still pictures and video
recording. Some phones also offer picture
editing software.

•It is also Possible to watch TV on a mobile
phone using EDGE/EGPRS (3G)
connectivity. Many mobile service providers
link up with various TV channels enable
users to enjoy mobile TV on the LCD screens
of their cell phones.
• Another popular applications of
multimedia phones is gaming. Some phones
are designed with special hardware and
software components in order to supports
better gaming experience for the user with
enhanced graphics and faster interactions
among the players.

Digital music players:
• Mobile computing encompass wide range
of applications include entertainment.
• Digital music players have revolutionized
the way people listen music. These players
include software that encode music format
such as MP3, WMA, Real media etc.
• Digital music players includes media
playing hardware that play an variety of
digital media file formats.
• The capacity of music player may vary
from 128 MB to 80 GB

• Some flash memory stick based players
can store 15,000 songs or more. Most flash
based players can serve as a storage
devices.
• Now a days media players enable video as
well audio playback.
Bluetooth and Wi-Fi:
• Bluetooth was invented by the Ericsson in
1994. it provide communication as a serial
COM port emulator and is an alternative to
RS-232 data cables.

• Bluetooth network is a self configuring
network, it creates Personal Area Networks
(PANs). It transfers the data with high level
of security it able to has eight networked
devices in one picocell. ( A picocell has
10m distance).
• Bluetooth is accepted as open wireless
technology by IEEE for exchanging the
data over short distances. It uses short
wavelength radio transmissions in fixed as
well as in mobile devices.

• Wi-Fi 802.11b and 802.11n supports data
transfer of 54 Mbps, 2.4 GHz and 600 MHz
respectively.
• 802.11b uses DSSS (Direct Sequence
Spread Spectrum)/ FHSS (Frequency
Hoping Spread Spectrum) and OFDM
(Orthogonal Frequency Division Multiple
access).
Global Positioning System(GPS):
• Today mobile phones have GPS receiver
which provides the current location of user
through its service provider.

• GPS receiver receives signals transmitted
by various GPS satellites orbiting the
earth. Timing circuits of all satellites are
synchronized.
• At least three GPS satellites are in the line
of sight of any location on the globe.
Assume satellites i, j, and K are in line of
sight at a location, these satellites provide
current geographical position of a mobile
device.
• The latitude and longitude values are used
to identify name of the location in the
mobile vicinity.

• The geographical location is continuously
changed on the map on the display when
the mobile device moves.
Gyroscope & Accelerometer:
• Gyroscope is a sensor which measures the
change in velocity as well as change in
direction. This measurement are used in
mobile gaming .
• Accelerometer is a sensor which detects
linear acceleration along three axis x, y
and z. Therefore it detects up/down,
right/left and front/back accelerations by
the user.

Digital compass & Magnetometer:
• A digital compass in a mobile phone shows
the directions north, south, east and west.
It also shows the direction in which the
phone’s display is inclined. It shows how
many degrees the device is inclined from
actual location.
• Magnetometer provides 3-dimensional
interactions without touch. Software
monitors the changes in magnetic fields
around the phone ad identifies user
gestures.

Camera: Today mobile phones have up to 12
Megapixel cameras by the Carl Zeiss
optics.
• These cameras have auto focus, LED flash
for pictures and videos. The pictures are
generally bmp, gif, or png formats.
2D and 3D Graph & HDMI:
• Smart phones support 2D and 3D graphics
and High Definition Multimedia Interface
(HDMI), these are used to transfer the
digital data without compression, in this
technique bandwidth is 340 MHz and data
transfer rate is 10.2 Gbps.

• It connects to computers, set-top boxes,
DVD players, and digital television.
Handheld pocket Computers:
• Handheld computing devices may available
in many forms, one of the example is
smart phones.
• However pocket computers different from
smart phones and multimedia phones in
that they can be programmed for
customized applications .
• pocket computers offer a variety of
applications and programming tools not
included in new generation mobile phones.

•Unlike smart phones, which usually use the
text-on-nine-keys format, handheld
computers have full text keypad or a touch
screen keypad.
• Stylus generally used to enter data into
handheld devices such as PDAs and
palmtops.
• Some allow the user to write on the screen
using a stylus and incorporate special
software for handwriting recognition.

• The handheld computers include word
processors and spread sheet software as
well as PIM software it also have QWERTY
keyboards or touch screens with stylus for
data inputs.
• Pocket PCs do not CD drives and hard disk
use flash memory or micro SD card and
allow the insertion of a memory stick as a
secondary storage.
• Clock speeds of pocket computer
processors are limited up to 200 MHz due
to considerations about battery life.

•Unlike laptops and notebooks, which use
regular microcomputer operating systems,
pocket computers have specially designed
operating systems.
• OS scaled to the requirements of the
software, hardware, and peripherals used in
handheld computers.
HANDHELD DEVICES (mobile OS)
• Not only the mobile hardware and software
the mobile operating systems also revolution
ally changed from past 20 years.
• The mobile OS provide interfaces, process
allocation and management and act as a
platform for sophisticated mobile soft wares.

• The following are features of some mobile
operating systems;
Windows CE:
• Windows CE is an operating system from
Microsoft. It is a real-time operating
system meant for handheld computers and
embedded systems.
• The Windows CE kernel is different from
the kernel of desktop versions of Windows.
It is meant for computing devices with low
storage and can be run in about 1 MB of
memory.

• There are various versions of Windows CE
to support different CPUs such as NEC
MIPS, Intel Strong-ARM, AMD X86, etc.
The following are Some of the features in
Windows CE devices:
• High resolution color/ display, touch
screen and stylus keypad.
• Complex APIs in Windows CE. It gives the
user a PC like feel and Windows like GUIs.
• PIM, MS office, Internet Explorer features
on handheld mobile system.
• The Compact Flash card slots to extend
memory and extension card slots.

•OS memory requirement is large but scales
to the requirement of the device peripherals.
• Built-in microphone for voice recording.
• USB port. A cradle connects to PC (A cradle
is an attachment on which the handheld
device can rest near a PC and connects to
the PC via a USB or serial port, Bluetooth,
or infrared).
• Infrared port to communicate with mobile
phones and external modems.
• Digital camera card.
• Games.

•Microsoft Windows Media player and other
media players.
•ActiveSync for synchronizing mobile data
with PC.
Mac OS:
•Mac OS is used in Apple iPhones. It has
four abstract layers.
•The first layer is for basic operations,
second for core services, third one is media
layer and fourth is the touch layer.
•The Mac require 500 MB but actual
requirements are depending on OS version.

• Mac provide faster response to user
interfaces, this API enables manipulation
of multi touch gestures.
Symbian OS:
• Symbain most widely used operating
system for smart phones, it runs
exclusively on ARM processors and its
structure much like that of some desktop
operating systems.
• Symbian offers pre-emptive multitasking,
multithreading and Memory protection. It
initially designed for handheld devices with
limited resources, strongly emphasizes on

• Symbian OS embodies event-based
programming and when applications are not
directly concerned with events, the CPU is
switched off, such techniques are very
useful in conserving battery life.
The following are some features of symbian
devices:
• Low boot time.
• Support for WLAN.
• One click connect to Internet.
• Improves performance of smart phones.
• Intelligent network management.
• Support for You Tube.
• High end security enhancement features.

Linux OS: Generally any mobile OS designed
for specific hardware and offer a platform
for selection of software applications. But
Linux changed these situations.
• It is an Operating System which support
different kinds of hardware and software
applications.
• It is an open source OS, it enables the
user to customize their device to suit their
specific needs.
• Linux to be more secure than most other
operating systems.

•Linux support is easily available from the
many forums and associations that promote
this OS.
• Many international mobile phone
manufacturers turning to Linux for their OS
requirements.
Android OS:
• Android allows developers to write the
managed code in Java. It allows controlling
of the mobile device via Google-developed
Java libraries.
• Android is a mobile operating system that
has a modified version of the Linux. It is free
and open source software.

The following are features of Android device:
• Multi-touch feature and supports devices
with various screen sizes and resolutions.
• Virtual keyboard layout for faster and
more accurate typing.
• Communicate instantly by tapping on the
contact.
• Sync feature which enables
synchronization of the files, images
between the PC and mobile.
• Choosing from all available
communication options (Face book,
Twitter, Yahoo! Mail, Gmail, etc).

• Multiple email account synchronization,
that combines all account into a single email
inbox with option of exchange support .
•Bluetooth API allows the device to connect
to other nearby devices. This capabilities
includes the integration of features of social-
interaction and P2P communication.
• Improved camera controls with digital
zoom, a scene mode, white balance controls,
macro focus and color effects.

E-Book Reader: Adobe offers in e-book
readers in multiple languages for pocket
PC and Symbian OS based mobile devices.
• e-book reader is a software running on
computers to read e-books news papers
and magazines.
SMART SYSTEMS
• Here we discuss smart systems that have
embedded computational devices.
• Smart systems provide comfort, efficiency,
and remote access to devices and
applications, the following are some smart
systems.

Smart Cards: Smart card is small, pocket-
sized card. It has electronic processing
circuits embedded in them. It can also
function as the memory cards, meant for
storing data.
• Smart card may also have embedded
microprocessor circuit. The size, shape,
electrical characteristics, communications
protocols, command formats, and
functions are defined by the ISO/IEC 7816
and ISO/IEC 7810 standards.
• Smart cards are two types contact smart
cards and contact less smart cards

• Contact smart cards have small gold
coated pins on the chip that provide
contact with the electrical circuit of the
card reader when card is inserted in it.
• The chip size of smart cards are few
millimetres and it lies in between inner
layers of the card.
• Smart card chip includes processing unit,
memory and transceiver and the cards
have secured hardware.
• The following are some applications of
smart cards

• A card is used for financial transactions as
a credit card or ATM/debit card.
• A card can store personal ID (even photo)
and personal information.
• A card can store the medical records of the
holder. (This may provide doctors a faster
way of accessing patient-records by reading
this card through a PC).
• An employee in an enterprise uses a card
to open the security locks at work and log
in.
• A student uses a card to get books issued
from the college library.

• Smart cards do not have batteries, the
energy is provided by the card reader.
• A smart card has a fabrication key,
personalization key, and utilization lock
embedded in it.
• Fabrication key identifies a card uniquely,
the host machine, remote server uses
personalization key, to activate the
transactions for which card is intended for,
utilization lock is used to lock or unlock
the use of card.
•

•The card can communicate with the host
after appropriate interchanges for
authentication. ASK 13.56 Mbps is used for
contact-less communication at data rates of
1 Mbps.
• A metallic squared foil at the side of the
card surface acts as the antenna for
transmitting signals to a host.
•The host is a device which reads the card
and performs requested transactions. The
host connects to a PC or remote server
through a phone line, Internet leased line,
fiber line.

Smart Labels: Generally labels serve the
purpose of identifying the contents of the
package.
• A label differs from card in terms of
thickness and visibility, and it using
wireless transmission for product
identification.
• A smart label has a processor, memory,
transceiver, and antenna.
• Labels are powered by the received signals
due to wireless communication the label
need not visible when implemented in
product or package.

• The smart labels networked together using
a central reading and computational
devices.
• We use collision sense and avoidance
protocols that multiple labels are not
allocated the same ID tag and then central
server can uniquely identify each one.
• A label may use secured hardware and
server authentication software.
RFID: It is a automatic identification method
for remote storage and retrieval of data on
RFID tags.

• RFID tags are objects that are attached
onto people, products, or animals to
enable their identification using radio
waves from near by source.
• RFID usually contains integrated circuit
and antenna supports up to 115 Kbps
data transfer.
• RFID computations are limited to
transmission of tag’s content.
• Each RFID tag is monitored by hotspot
which is in the area of tag and has a line of
sight access to it.

• The hotspot has a computer and wireless
transceivers to transmit and receive
signals from RFID tag.
• The distance between RFID and hotspot is
less than 20cm then a device use NFC
protocol.
Smart Tokens: Tokens are used for
authentication purpose, such as granting
entry into a restricted area, etc.
• A smart token is an encapsulated circuit
consists of embedded processor and
memory.

• The size of the smart token is small and
use wire based protocol and communicate
16-128 kbps for connection less
communication.
• The following are some examples of smart
tokens;
1.For granting permission to employees to
enter work place.
2.Token is used to remotely open doors.
3.Defence applications.

Sensors: Sensors are electronic devices that
sense the physical environment, For
example, sensors for temperature, pressure,
light, metal, smoke, and proximity to an
object.
• Sensor sends the signals to a computer or
controller facilitate interaction of the mobile
device with the surroundings.
• The following are some examples of
sensors;
1. A CCD (charge-coupled device) camera to
identify various objects or a microphone to
recognize voices.

• Sensor for background noise is used to
control voice amplification during a call.
• Sensor for surrounding light used to
control the brightness of the LCD screen.
• The SPS (Speech Processing System)
authenticates the mobile owner then, the
SPS can also be used to dial a spoken
number and interpret and execute spoken
commands.
• A sensor for measuring the strength of the
signal received controls the amplifications of
received signals.

Actuator: Actuator receives the signals from
a controller or central computer and
accordingly activates a physical device,
appliance, or system.
• sensor actuator pair are used in control
systems, for example, a temperature sensor
and current actuator pair controls the oven
temperature.
• A light sensor and bulb current actuator
pair controls the light levels
• A pressure sensor and valve actuator pair
controls the pressure

Smart appliances: With the present
automation technology, it is possible to
control home appliance and security
systems using cell phones.
• It is possible to networked home
appliances which use the power lines are
able to carry data frequencies up to 525
KHz.
• We know that smart home devices are we
enabled services, so we are able to allot
web address (IP address) and these devices
are generally connected to the internet
through residential gateway.

• The gateway allow the user to access home
appliance from outside using WLAN,
internet, or access point of mobile service
provider.
Setup Boxes:
• A set-top box is a sophisticated computer-
based device. It has data, media, and
network processing capabilities.
• It interconnects the home TV and the
broadcasting service network. Java is the
most commonly used programming
language in a setup box.

• Setup boxes run decoding and encoding
software. There is a software component,
called a device agent, which administers
the device on behalf of the service provider.
• Setup box sends its output signal to
telephone lines, cable lines, and wireless
antennae, it also provide feedback
channels for interactive TV, web browsing.
• The setup box gets signal from wireless
antennae, cable lines, telephone lines, and
dish antennae.

LIMITATIONS OF MOBILE DEVICES
• Mobile devices are limited in various ways
such as hardware limitations, quality of
mobile service, security during
communication and transmission,
connectivity troubles, etc.
• Quality and Security of Service: Technical
restrictions and practical considerations, it
is difficult for service providers and device
manufactures to ensure that the mobile
device operations run uninterrupted.

• Accessibility: Each mobile device is
limited by accessibility constraints. For
example RFID has limited ranges and line
of sight hot spot.
• Range: Signal strength is inversely
proportional to the square of the distance
from the transmission source. In addition
to this there is degradation of signal
quality due to reflection, scattering, and
diffraction.

• Connectivity: There may be connectivity
loss or intermittent connectivity in certain
situations. The atmospheric conditions
and changes in environment affect signal
strength.
• Security: A mobile device has security
constraints. Unsolicited advertisements
and unwanted messages may delivered to
a device. Virus attacks on mobile devices
can cause a software crash or even corrupt
the hardware.

• Hackers may hack into a device and
render it functionless or threaten integrity
and security of the data stored on the
device.
• Mobility: Non-availability of an access point
or base station and other infrastructural
issues restrict the mobility of a device.
• Energy Constraints: All mobile devices have
limited energy stored in their battery. Also,
battery size and power are limited due to
considerations such as size, weight, and
bulk of mobile devices. The devices
therefore need to be recharged after short
periods of time.

• Hardware Limitations: Besides energy
limitations due to battery size, all mobile
devices face various other hardware
constraints too.
• Memory There are constraints on memory
availability. Most mobile devices do not
support hard-disk drives and CD drives
due to size limitations.
• Bandwidth: Limited bandwidth may become
an obstacle to seamless connectivity and
quality of signals, when a large number of
mobile devices simultaneously demand
network connectivity.

UNIT –III
GSM & Other 2G Architectures
Introduction to GSM: To day the most
successful digital mobile telecommunication
system is G.S.M. its original name is “Groupe
speciale mobile” was founded in 1982. Its
name soon changed as “Global system for
mobile communications”, with specification of
procedures designed by European
Telecommunications standards Institute
(ETSI) after that the universal mobile
Telecommunication systems (UMTS) add new
standards to G.S.M.

• The primary goal of G.S.M was to provide a
mobile phone system that allows users to
roam seamlessly and provide voice services
compatible to ISDN and PSTN systems.
• There are several versions in GSM depending
on various standards and different uplink
and downlink frequencies.
1. GSM 900-it is initial version of GSM
developed in Europe using 890-915 MHz
uplink and 935-960mhz down link frequency.
2. DCS 1800-digital cellular system is a version
of GSM using 1710-1785 MHz up link and
1805-1880 MHz down link frequencies.

3. PCS 1900- personal communication service
is a version of GSM using 1850-1910 MHz
uplink and 1930-1990 MHz down link
frequencies.
4. GSM-R (Rail)-this version of GSM offers
many additional services which are un-
available with public GSM. It offers 19 channels
for voice and data traffic .other services are,
emergency calls with acknowledgement, voice
group call service, voice broadcast service etc.

GSM (Mobile) services
• GSM permits the integration of different voice
and data services that compatible with existing
networks. The GSM has defined three different
categories of services these are,
1. Bearer services.
2. Tele services.
3. Supplementary services.
The following is the GSM service reference
model.

• In the service model A mobile station ’MS’ is
connected to GSM-Public Land Mobile
Network (PLMN) via Um interface. This is
further connected to transit network, such as
Integrated Services Digital Network (ISDN) or
Public Switched Telephone Network (PSTN).
• There may be additional source/destination
network before another terminal ‘TE’. within
the MT there is a mobile station MS.
• The mobile termination ’MT’ performs all
network specific tasks and also offers an
interface for data transmission to ’MS’ which
is the network independent.

Barrier Services: In classical GSM model,
bearer services are connection oriented and
circuit or packet switched. These services
only need the three lower layers of OSI
reference model. The bearer services may be
transparent and non transparent,
synchronous or asynchronous, data
transmission.
• Barrier services are again classified into;
1. Transparent Barrier Services.
2. Non Transparent Barrier Services.
3. Synchronous Services.
4. Asynchronous Services.

Transparent Barrier Services: which use the
functions of physical layer to transmit
data. Here data transmission has constant
delay and throughput if no transmission
errors occurs. To improve the quality of
transmission, this method use Forward
Error Correction (FEC)-which reconstructs
the original data incase of transmission
errors.
Non Transparent Barrier Services: which use
the second and third layer protocols to
implement errors correction and flow
control. Here we use transparent services

• This protocol contains High level Data Link
Control (HDLC) and selective-reject
technique to retransmission of erroneous
data. In Non transparent bearer service the
error rate is less than 107, but the
throughput and delay vary depending on
transmission quality.
Synchronous Data Transmission: It
indicates that the data transmitted from
transceiver at a fixed rate as the result
constant phase difference maintained
between successive data bits or frames.

• The receiver must synchronize clock rate
according the incoming data bits. The
receivers also synchronize data bits
coming in from multiple paths or stations
and compensate for the varied delays in
receiving signals.
• Handshaking is not used in synchronous
transmission of data and synchronous
data transmission is faster because there
is no waiting period during the data
transfer.

Asynchronous Data Transmission: Here the
data is transmitted by the transceiver at
variable rates as a result of constant time
intervals are not continuously maintained
between consecutive data frames. Usually
handshaking or acknowledgement of data
in asynchronous data transfer.
• Even if there is no acknowledgement when
the data flow is maintained by using FEC
and buffers. Buffers can use variable delay
in reception.

Tele Services: GSM tele services are end-to-
end that is from one terminal TE to
another, these are application specific and
need all seven layers of OSI model. The
following different tele services offered by
G.S.M.
1) telephony- The main focus of GSM is to
provide voice oriented tele services. Here
special codes are used for voice
transmission, other codes used for analog
data communication with traditional
computer modems.

2) Emergency Number- In this service, the
same number can be used throughout
specific area. It is a mandatory (compulsory)
service offered by service providers at free of
cost. This service has the highest priority
and will be set up with the closest
emergency center.
3) Short Message Service (SMS) – it is a
useful service to transfer short messages
upto160 characters. This service do not use
standard data channel of GSM, but using
unused capacity in the signaling channels.

•Sending and receiving of SMS is possible
during voice or data transmission.
4) Enhanced message service (EMS)- which
support large message size, formatted text,
animated pictures, small images and ring
tones in a standardized away. EMS never
create hurdles to MMS multimedia message
service, which offers transmission of large
pictures, short video clips etc.

5) Group 3 FAX- this is another Non voice
Tele service is available world wide.

• In this service FAX data is transmitted is
digital data over the analog telephone
network according to the ITU-T standards.
Supplementary services: Supplementary
services are enhancements for standard
telephony services, and may vary from
provider to provider. These services are
user identification, call redirection, call
forwarding, closed user group and
multiparty communication calls.

GSM Architecture
The GSM has hierarchical, complex, system
architecture containing many entities,
interfaces, and acronyms. A GSM system
contains three subsystems,

1. Radio Sub System (RSS)
2. Network and switching Sub System (NSS).
3. Operating Sub System (DSS).

The following is the functional architecture
of GSM.

• In the above figure the RSS and NSS are
connected through ‘A’ Interface and
connection to OSS through ‘O’ interface.
The ‘A’ interface is circuit-switched based
and ‘O’ interface is signaling system based.
Radio Sub System: The top level radio sub
system contains all radio specific entities,
such as base station sub system (BSS),
mobile stations (MS), and Base transceiver
station (BTS), base station controller
(BSS) .etc...

A) Base station sub system (BSS): A GSM
network contains many BSS. Each
controlled by a Base Station Controller
(BSC). The BSS performs all activities to
maintain radio connection to MS, such as
coding/decoding of voice, rate adoption, etc.
the BSS contains many BTSs.
B) Base transceiver station (BTS): A BTS
contains all radio equipment, such as
antennas, signal processing, and amplifiers
required for radio transmission, the BTS can
form a radio cell by using sectorized
antennas and it contains several MSs. The
connection between BTS and MS through
‘Um’ interface and BSC through ‘Abis’
interface.

• An ‘Um’ interface contains all techniques
for wireless transmission and ‘Abis’
interface contains 64Kbit/s connections.
C) Base station controller (BSC): It is basically
manages the BTSs. It reserves radio
frequencies, handles hand over from one
BTS to another BTS with in BSS and
performs paging of MS. The BSC also
multiplex paging of radio channels into the
fixed network connections.

D) Mobile Station (MS): It is independent user
equipment, contains hardware and
software of Subscriber Identity Module
(SIM), which stores all user specific data
that is relevant to GSM.
• The user can personalize MS by his /her
SIM without SIM only emergency calls are
possible.
• Any MS is identified through International
Mobile Equipment Identity (IMEI). The
device specific techniques such as theft
protection are supported by IMEI.

• The SIM have many user subscribed
identifiers, labels and services such as a
Personal Identity Number (PIN), A PIN UN
block Key (PUK), an authentication key ‘Ki’
and International Mobile Subscriber
Identity (IMSI) and Location Area
Identification (LAI).
• The MS also offers other interfaces to
users with display, loudspeaker,
microphone and programmable soft keys.

Network and Switching Sub System: The
network and switching sub system is the
heart of the GSM network, which connects
wireless networks.
•The NSS carries out handovers between
different BSSs and contain techniques for
world wide localization of users and also
supports charging, accounting, and roaming
of users between different service providers
in different countries.
• The NSS contain following switches and
databases.

A) Mobile Service switching Center (MSC): It is a
high performance digital ISDN switch,
which setup connections to other MSCs
and to the BSCs. through the ‘A’ interface.
• It is a fixed back bone network of GSM
system, which manages several BSCs in a
geographical region.
• An MSC handles all signaling needed for
connection setup, connection release and
handover of connections between MSCs,
by using the standard signaling system
No 7 (SS7).

• The MSC can also perform all
supplementary services such as call
forwarding, multiparty calls etc...
B) Home Location Register (HLR): It is the
most important database in GSM system
and stores all user relevant information.
• The HLR consists of static information
such as the mobile subscriber ISDN
number (MSISDN) and International
Mobile Subscriber Identity (IMSI).

•The HLR may also contain dynamic
information, such as, current location area
(LA) of MS, Mobile Subscriber Roaming
Number (MSRN). As soon as MS leaves its
current LA, the information in HLR is
updated.
C) Visitor Location Register (VLR): It is a
dynamic database associated with each
MSC, which stores all important information
required for users currently in the LA.
•If new MS comes into LA the VLR is
responsible for it, copies all relevant
information of this user from HLR.

• This hierarchy of VLR and HLR avoids
frequent HLR updates and long distance
signaling of user information.
3) Operation Sub System: The operation sub
system contains the necessary functions
for network operation and maintenance.
The OSS processes network entities of its
own and access other entities through SS7
signaling. The following are some entities
in OSS.

A) Operation and Maintenance center
(OMC):
The OMC monitors and controls all other
network entities Via ‘O’ interface.
•The functions are, traffic monitoring, status
reports, subscriber and security
management, accounting and billing.
•To carry out above functions the OMC use
the concept of Telecommunication
Management Network standard (TMN) by
ITU-T (International Telecommunication
Union-Telecommunication Sector).
B) Authentication Center (AUC): An
authentication center is defined to protect

•The AUC contains algorithms for
authentication, encryption keys, and
generate values for user authentication in
HLR. Actually the AUC exists in the special
protection part of HLR.
C) Equipment Identity Register (EIR): The
EIR is the database which stores all device
identifications (IMEI) registered for the
network.
•The EIR also contains a list of valid IMEIs
and a list of malfunctioning devices.

RADIO INTERFACES OF GSM
• The radio interface illustrates the
connection or communication between
Base Transceiver Station (BTS) and Mobile
Station (MS). It also determines the
process of channel allocation for data
transmission.
• In GSM system, the Um radio interface is
the most significant one. It contains many
mechanisms for multiplexing and media
(channel) access.

• Generally the GSM uses space division
multiple access (SDMA) with in a BTS to
establish communication between MS and
BTS. Further, the GSM uses frequency
division duplex (FDD) to separate uplink
and down link. So the GSM media access
combines both TDMA and FDMS.
• The GSM 900 uses 248 channels for
uplink and downlink, each has 200 KHz
wide. Due to the technical reasons channel
1 and 124 is not used, 32 channels are
reserved for organizational data and
remaining 90 used for customers

•That is;
Uplink channels: 124
Down link channels: 124
Total channels : 248
Organizational Data: 32
User Data: 90
Unused: 02
Total channels: 124
• The following diagram illustrates the frame
hierarchy of GSM

• As shown in the figure, each 248 channels
are separated by GSM-TDMA frame that is
every 200 KHz carrier (Channel) is divided
into smaller frames. The time duration the
frame is 4.155ms.
• A GSM frame is again subdivided into
eight (8) GSM time slots. The transmission
time of the GS M time slot is 577µs.
• The data is transmitted in small portions
called bursts. The above figure shows the
GSM normal burst; which indicates data
transmission within a time slot.

•The each time slot is able to transmit 148
bits which can take 546 µs the remaining
time 31 µs are used as guard space to avoid
overlapping with other bursts. The GSM
time slot is divided into;

Trail bits: 06
Flag bits(S) 02
Training bits 26
User data bits 114
Total bits in the GSM time slot is 148 bits.
•

• Suppose if you fill the whole slot with data
for transmission 156.25 bits with 577 µs.
so the each physical TDM channel has a
raw data rate 33.8 Kbits/s, so each radio
carrier approximately transmits 270
Kbits/s over Um interface.
• The first and last bits of time slot that is
trail bits are set to 0 (zero) can be used to
enhance the performance of receiver.
• The training bits are used to adopt the
parameters of receiver to the current path
propagation characteristics.

• The flag bits ‘S’ indicates whether data
field contains user or network data.
• In addition to the normal burst, the GSM
defines four more bursts.
1. Frequency correction burst.
2. Synchronization burst.
3. Access burst.
4. Dummy burst.
• Frequency Correction Burst: This burst
can allow the MS to correct the frequency
of local oscillator to avoid interference with
neighboring channels.

• Synchronization Burst: this is the
extension of training sequence to
synchronize the MS with the BTS in time.
• Access Burst: This is used for initial
connection setup between MS and BTS.
• Dummy Burst: It is used if no data is
available for a slot.
Logical Channel Allocation:
The GSM specifies two basic groups of
logical channels;
1. Traffic channels.
2. Control channels.

• Traffic Channels (TCH): The GSM uses
TCH to transmit user data such as voice
and fax. There are two categories of TCH
one is TCH full rate (TCH/F) and another
one is TCH half rate (TCH/H)
• The TCH/F can transmit the data with
rate 22.8 kbits/s and TCH/H transmit the
data with rate 11.4 Kbits/s. But we know
that the GSM uses 13 Kbits/s standard
rates to transmit the voice data with
quality.

• Suppose we can use TCH/H for the voice
data transmission, it doubles the capacity
of the GSM system, but the quality of the
speech decreases.
• Suppose we use TCH/F for the data
transmission the remaining capacity, that
is 22.8 – 13 Kbits/s = 9.8 Kbits/s was
used for error correction.
• The GSM uses standard codes for
transmission of voice, such as full rate (13
Kbits/s) Half rate (5.6 Kbits/s) and
Enhanced Full Rate ((EFR) for better
quality and low transmission errors.

• For higher quality of data transmission,
GSM uses Tandem Free Operation (TFO).
In this mode the two MSS are directly
exchange the voice data.
• Not only voice transmission, the data
transmission is also possible in GSM at
different data rates, example TCH/F 4.8
for 4.8 Kbits/s, TCH/F 9.6 for 9.6 kbits/s
and TCH/F 14.4 for 14.4 Kbits/s.
• The logical channels differ in terms of their
coding schemas and error correction
capabilities.

• Control Channels (CCH): Many CCHs are
used in GSM to control medium access,
allocation of traffic channels or mobility
management. Each of channels in this
group is again categories into several sub
channels.
1 Broadcast control channel (BCCH): A BTS
uses this channel to signal information to
all MSs within a cell. Information
transmitted in this channel is, the cell
identifier, options available within the cell
and frequencies available inside the cell
and neighboring cells. The following are

a) Frequency correction channel (FCCH): A
BTS sends frequency correction
information through this channel.
b) Synchronization channel (SCH): The BTS
sends the time synchronization
information through this channel.
2.Communication control channel (CCH):
The CCH is used to exchange all the
information regarding connection setup
between MS and BTS. The following are the
sub channels of CCH.
•

a) Paging channel (PCH): For the calls
towards an MS, the BTS uses the paging
channel for paging the appropriate MS.
b) Random Access Channel (RACH): If MS
wants to (establish) setup a call, it uses
random access channel to send data to the
BTS.
c) Access Grant Channel (AGCH): The BTS
uses access grant channel to signal an MS
that it can use a TCH or SDCCH for further
connection setup.

3. Dedicated Control Channel (DCCH): All the
above channels are unidirectional, but
dedicated control channels are
bidirectional. The following are sub
channels of DCCH.
a) Stand alone Dedicated Control Channel
(SDCCH): As long as MS has not
established a TCH with BTS, it uses
SDCCH with low data rate for signaling. It
consists of authentication, registration or
other data needed to setup a TCH.

b) Slow Associated Dedicated Control
Channel (SACCH): Each TCH associated
with Slow Associated Dedicated Control
Channel (SACCH), to exchange the system
information, channel quality, signal power
level etc…
c) Fast Associated Dedicated Control
Channel (FACCH): When TCH is already
exists, more signaling information is
required and then GSM uses FACCH. It
uses the time slots which are otherwise
used by TCH.

• The FACCH is necessary in case of
handovers where BTS and MS have to
exchange larger amounts of data in less
time.
Frames Hierarchy:
• The GSM specifies a complex multiplexing
scheme that integrates several hierarchies
of frames. Suppose we use TCH/F for user
data transmission each TCH/F has
associated with SACCH for slow signaling
and FACCH for fast signaling. A typical
usage of physical channel for data
transmission is shown bellow.

TTTTTTTTTTTTSTTTTTTTTTTTTX
TTTTTTTTTTTTSTTTTTTTTTTTTX

• In the above data transmission T-indicates
the user data, S-indicates signaling slot and
x-is unused slot
• Twelve slots of user data followed by
signaling slot again twelve slots of user data,
then an unused slot, these 26 slots are
repeated over and over again. But actually
24 out of 26 slots (2 unused) are used by
TCH/F for data transmission.

• We know that 114 bits of user data
transmitted in a normal burst, which is
repeated for every 4.165 ms. this results
the data transmission rate is 24.7 Kbits/s.
the TCH/F actually use 24/26 of slots, so
the final data rate is 22.8 Kbit/s. (for
TCH/F)
• The periodic patterns of 26 slots occur in
all TDMA frame with TCH. The logical
combination of these frames which carry
user traffic is called traffic multi frame.

• Suppose it contains signaling data then it
called control frame. The combination of
26 frames have to a multi frame takes 120
ms duration. The control frame consists of
51 TDMA frames have duration 235.4 ms.
• The logical frame hierarchy, combining 26
data frames with 51 control frames or 51
control frames with 26 data frames. The
2048 multi frames form a hyper frame with
duration 3.5 hours.

• The large logical structure is needed for
encryption. The GSM counts each TDMA
frame with frame number forming input
for the encryption algorithm. The frame
number and slot number uniquely identify
each time slot in GSM.
PROTOCOLS OF GSM
• The following diagram shows the protocol
structure of GSM, which consists of
signaling protocols, interfaces and some
entities

• In the above the Um interface is play an
important role, between the objects in a
fixed network

LAYER-1: the physical later at MS handles
all radio specific functions, such as,
a) Multiplexing of bursts into TDMA frames.
b) Synchronization of MS with the BTS.
c) Detection of idle channels.
d) Measurement of channel quality on the
downlink.
•The physical layer at Um interface uses
Gaussian Minimum Shift Keying (GMSK)
technique for digital modulation and
performs encryption and decryption of the
data.

• But in GSM the encryption in not
performed end-to-end, it is between Ms
and BTS with in air.
• The synchronization used for the
correction of individual path delays
between MS and BTS. All MSs with in a
cell can use the same BTS and must be
synchronized with this BTS
• The BTS generate time structure of slots or
frame for the synchronization.
• A major problem in synchronization is
different round trip times (RTT).

• An MS very close to BTS has a very short
RTT other wise the RTT will increase
• The main task of the physical layer in GSM
protocol architecture is channel coding
and error detection/ correction
• The channel coding use the different
Forward Error Correction schemes (FEC).
FEC adds redundancy to user data for
detection and correction of selected errors
• Different logical channels of GSM use
different coding schemes with different
correction capabilities

• LAYER-2: The protocol existed with in
second layer of GSM protocol architecture
is Link Access Procedure for D-Channel
(LAPDm), which is used to signaling
between the other GSM network entities
• The LAPD which is generally used in ISDN
systems and it is a version of High Level
Data Link Control (HDLC)
• The LAPDm offers reliable data transfer
over connections, resequencing of data
frames, and flow control

• The LAPDm is a light weight protocol
because it does not require
synchronization of flags or checksums for
error detection and correction
• There is no buffer space between layer-1
and layer-2 so LAPDm accepts frame
structure, recurrence patterns etc defined
at Um interface
LAYER-3: The third layer in GSM protocol
architecture may also called network layer.
This layer contains many sub layers

• The lowest sub layer is Radio Resource
Management (RR). The some part of the RR
is implemented at BTS and remaining part
is implemented at BSC
• The function of RR is supported by BSC
by using BTS management
• The main task of RR is to setup, maintain
and release of radio channels. The RR can
directly access the physical layer for radio
information and offers a reliable
connection to next higher layers

LAYER-4: The fourth layer is Mobility
Management (MM) contain functions for
registration, authentication, location
updating and also provide Temporary
Mobile Subscriber Identity (TMSI) which is
used to replace the International Mobile
Subscriber Identity (IMSI).
• The TMSI hides the real identity of an MS
user over the air interface. The MM offers a
reliable connection to the next higher
layers

LAYER-5: The final layer is Call Management
(CM) layer which contain three entities.
a) Call Control (CC).
b) Short Message Service (SMS).
c) Supplementary Service (SS).
• Call Control (CC): This provides a point-to-
point connection between two terminals and
is used by higher layers for call
establishment, call clearing, and change of
call parameters
•This entity also provides functions to send
in-band tones, called Dual Tone Multiple
Frequency (DTMF)

• Short Message Service (SMS): It allows for
message transfer using control channels
SDCCH and SACCH
• Supplementary Services (SS): These
services are enhancement of standard
telephony services and these may vary
from provider to provider
• The supplementary services may be user
identification, call redirection, forwarding,
closed user groups and multiparty
communication

GSM Localization
• One fundamental feature of GSM is
automatic world wide localization of users.
The GSM system always knows the users
current location and the same phone
number is valid world wide
• To provide localization of uses the GSM
performs periodic location updates even if
the user does not use mobile station
• The HLR always have the information
about current location and the VLR is
responsible for the MS where it is and
informs to the HLR about location changes

• When MS moves from one VLR to another
VLR the HLR sends all user data needed to
the new VLR
• Changing VLR with uninterrupted
availability of all services is also called
roaming. To locate the MS and to address
the MS several numbers are needed
• Mobile Station International ISDN Number
(MSISDN): The only important number for
user of GSM is pone number. The phone
number is associated with SIM, which is
personalized for a user

• The MSISDN follows ITU-T standard for
addresses and it also used in fixed ISDN
networks
• This number consists of Country Code
(CC), example for India +91, the National
Destination Code (NDC), which addresses
the network provider for example 984 for
idea network and Subscriber Number (SN)
• International Mobile Subscriber Identity
(IMSI): The GSM uses the IMSI for internal
unique identification of subscriber.

• The IMSI consists of Mobile Country Code
(MCC), the Mobile Network Code (MNC)
and Mobile Subscriber Identification
Number (MSIN)
• Temporary Mobile Subscriber Identity
(TMSI): The GSM uses the 4 byte TMSI for
local subscribe identification to hide the
IMSI. The TMSI is selected by current VLR
and is only valid with in the location area
of VLR, additionally the VLR may change
the TMSI periodically

• Mobile Station Roaming Number (MSRN):
The MSRN is a temporary address that
hides the identity and location of
subscriber. This address is generated by
the VLR on the request of MSC
• This address contains current Visitor
Country Code (VCC), Visitor National
Destination Code (VNDC). The MSRN helps
to find a subscriber for an incoming call
• The following is the call organization
procedure in GSM network. In GSM
network there are two types of calls,

a) Mobile Terminated Call (MTC).
b) Mobile Originated Call (MOC).
• Mobile Terminated Call (MTC): In this
situation an outside network subscriber
calling a mobile station in GSM network.
The following is the diagram

• In MTC, A user dials the phone number of
GSM subscriber. The Public Switching
Telephone Network (PSTN) notices that the
number belongs to the user in GSM
network and forward the call to GMSC
• Now the GMSC forward this information to
the HLR for subscriber identification and
signals
• Here the HLR checks whether the number
exists and whether the user has
subscribed requested services and also
requests the MSRN from current VLR

• After receiving MSRN from VLR the HLR
forward this information to GMSC. Now
the GMSC forward the call setup request
to MSC
• On this point the MSC request the current
status of MS from VLR. If MS is available,
the MSC initiates paging signal to the
BTSs of all BSSs
• . At this point the paging signal is transmit
to the MS. Of the MS response, the VLR
signals to MSC to setup a connection to
the MS

• Mobile Originated Call: The Mobile
Originated Call is a simple procedure then
the Mobile Terminated Call. The following
is the diagram

• In MOC the MS transmit a request for new
connection to the BSS and then it is
forwards this request to the MSC
• Now the MSC checks if this user is allowed
to setup a call with the requested service
and checks the availability of resources
through the GSM network and into the
PSTN
• If all resources are available, the MSC
setup a connection between the MS and
fixed network.

• The following is the flow of messages
during MOC.
1. The MS request the BTS to grant a
channel for communication and BTS
immediately responds by assigning
channel to MS.
2. MS sends a request to BTS for service and
BTS replies with authentication to MS.
3. BTS sends a command for ciphering at
MS, cipher number generated by AuC and
cipher key is available at BTS for accessing
MS.

4. Now MS runs an algorithm on cipher
number sent by BTS and the key is stored
in SIM.
5. Now call is setup by call Management
protocol (CM) by the MS and BTSM
protocol by BTS.
6. Call setup is conformed by BTS to MS.
7. Assignment command is sent by BTS to
MS and assignment complete is sent by
MS to BTS.
8. An alert message is sent from BTS to MS
before connection.

9. Connection established message is sent
from BTS to MS and connection
acknowledgement is sent by MS to BTS.
10. Voice or data interchange starts.
• The following is the flow of messages
during MTC.
1. The BTS sends a request for paging to MS
and MS request to BTS for channel
allocation.
2. Channel is immediately assigned by BTS
to MS and MS responds to paging signal to
BTS.

3. A request for authentication is sent by the
BTS and response is sent by the MS.
4. BTS sends the ciphering command and
MS responds with cipher complete
message.
5. Call is setup by running CM protocol at
MS and BTSM protocol at BTS.
6. Now assignment command is sent by BTS
and MS responds with assignment
complete.
7. Before connection establishment alert
message sent by BTS to MS.

8. Connection established message is sent
by BTS to MS and acknowledgement
message is sent by MS to BTS.
9. Voice or data transmission begins.
END OF UNIT - III

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