Chapter-1

BHARAT SANCHAR NIGAM LIMITED

1.1 INTRODUCTION :-

Type Communication Service Provider

Availability Countrywide except Delhi & Mumbai

Owner The Government of India

Key people R. K. UPADHYAY (Chairman & MD)

Founded 19th century, incorporated 2000

Website www.bsnl.in

Table 1.1- Introduction

Bharat Sanchar Nigam Limited (abbreviated BSNL) is an Indian state-owned

telecommunications company headquartered in New Delhi, India. It is the largest

provider of fixed telephony and fourth largest mobile telephony provider in India, and is

also a provider of broadband services. However, in recent years the company's revenue

and market share plunged into heavy losses due to intense competition in Indian

telecommunications sector BSNL is India's oldest and largest communication service

provider It had a customer base of 95 million as of June 2011 It has footprints throughout

India except for the metropolitan cities of Mumbai and New Delhi, which are managed by

Mahanagar Telephone Nigam Limited (MTNL). “BHARAT SANCHAR NIGAM

LIMITED” is abbreviated as BSNL. It is fourth largest department of Telecommunication

Company in Asia and seventh in world today. This is one of the most earning revenue in

India. Above more than 3 laces employees, officer and engineers working in BSNL at

present. Previously electro mechanically exchanges for use in India namely stronger type

exchange, cross bar exchange were there. These manual telephone exchanges suffered

from some disadvantages. To overcome these automatic exchanges was introduced in this

system.

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In 1980’s PITHROTHA LTD. Introduced “C-DOT” exchange in India. These exchanges

replaced by electro mechanical exchange. This exchange which has wide range of

capacity replaced electromechanical exchange, C-DOT-128, C-DOT-256, C-DOT-512,

C-DOT-1024(SBM) exchange, C-DOT-2048(MBM) exchange and so on. Besides C-

DOT exchange ILT exchange, E-10B exchange also proved of mild stone in

Telecommunication Sector to replace electromechanical exchanges, which were most

sophisticated and modern latest techniques electronics exchanges. There after it was

OCB-283 exchange which proved very important exchange in this series to replace

electro mechanical exchanges. Now it is “WLL” & “GSM” mobiles which is also proved

a mild stone in Telecommunication sector. It was 31st march 2002 when BSNL started

these GSM mobile and today it has provided almost 35 lacks mobiles in all over country.

WLL system which is also a mobile with limited mobility in city & can have Tele

communication facility in that area almost. While GSM can cover all cities of the country.

C-DOT provides the following facilities:

• Telegraph services

• Telephone services such as Local calls, Trunk calls, Overseas calls etc.

• Wireless services including mobile wireless services for police, defense,departments, etc

• Renting of Broadcast & TV channels

• Telecom Bureau Services

• Data Services

• FAX Services

1.2 BSNL SERVICES: - BSNL provides almost every telecom service in India.

Following are the main telecom services provided by BSNL.

Universal Telecom Services: Fixed wire line services and landline in local loop

(WLL) using CDMA Technology called bfone and Tarang respectively. As of

June 30, 2010, BSNL had 75% market share of fixed lines.

Cellular Mobile Telephone Services: BSNL is major provider of Cellular Mobile

Telephone services using GSM platform under the brand name Cellone & Excel

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(BSNL Mobile). As of June 30, 2010 BSNL has 13.50% share of mobile

telephony in the country.

Internet: BSNL provides Internet access services through dial-up connection (as

Sancharnet) as Prepaid, (NetOne) as Postpaid and ADSL broadband (BSNL

Broadband). BSNL held 55.76% of the market share with reported subscriber base

of 9.19 million Internet subscribers with 7.79% of growth at the end of March

2010.

Intelligent Network (IN): BSNL offers value-added services, such as Free Phone

Service (FPH), India Telephone Card (Prepaid card), Account Card Calling

(ACC), Virtual Private Network (VPN), Tele-voting, Premium Rae Service

(PRM), Universal Access Number (UAN).

3G: BSNL offers the '3G' or the'3rd Generation' services which includes facilities

like video calling, mobile broadband, live TV, 3G Video portal, streaming

services like online full length movies and video on demand etc.

IPTV: BSNL also offers the 'Internet Protocol Television' facility which enables

watch television through internet.

FTTH: Fibre to The Home facility that offers a higher bandwidth for data

transfer. This idea was proposed on post-December 2009.

VVOIP: BSNL, along with Sai Info system - an Information and Communication

Technologies (ICTs) provider - has launched Voice and Video Over Internet

Protocol (VVoIP). This will allow making audio as well as video calls to any

landline, mobile, or IP phone anywhere in the world, provided that the requisite

video phone equipment is available at both ends.

1.3 BSNL EXCHNGE : - Exchange view of BSNL

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Fig. 1.1 BSNL Exchange Antenna

1.3.1 MAKING A TELEPHONE CALL: - A telephone call starts when the caller lifts the

handsets of the base. Once the dial tone is heard, the caller uses a rotary or a push button

dial mounted either on the handset or on the base to enter a sequence of digits, the

telephone number of called party. The switching equipment from the exchange removes

the dial tone from the line after the first digit is received and after receiving the last digit,

determines the called party is in the same exchange or a different ones. If the called is in

the same exchange, burst of ringing current is applied to the called party’s line. Each

telephone contains a ringer that responds to specific electric frequency. When the called

party answers the telephone by picking up the handset, steady start to flow in the called

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party’s line and is detected by the exchange. The exchange than stops applying ringing

and sets up the connection between the caller and the called party. If the called party is in

different exchange from the caller, the caller exchange set up the connection over the

telephone network to the called party’s exchange. The called party then handles the

process of ringing, detecting an answer, and notifying the calling and billing machinery

when the call is completed. When conversation is over, one or both parties hang up by

replacing their handset on the base, stopping the flow of current. The exchange when

initiates the process of taking down the connection, including notifying billing equipment

of the duration of the call if appropriate.

1.3.2 ABOUT THE EXCHANGE: - All telephone subscribers are served by automatic

exchanges, which perform the functions, the human operator. The number being dialed is

stored and then passed to the exchange’s central computer, which in turns operates the

switching to complete the call or routes it a higher level switch for further processing.

Today’s automatic exchanges uses a pair of computers, one running the program that

provides services and the second monitoring the operation of the first, ready to take over

in a few seconds in the event of equipment failure.

Different type of exchanges present in BSNL is:

E-10B

OCB283

EWSD

Purpose of all exchange which are:

1. subscribers connection unit

2. switching network (CX)

3. control unit

4. OMC

For smooth working of an exchange following unit are very important:-

1. Computer Unit: - it deals with additional services of the exchange to the

customers with the help of computers.

2. Power Plant: - to feed proper power supply to exchange.

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3. AC Plant: - to maintain the continuous temperature + or – 2 degree Celsius to the

digital switch (exchange).

4. MDF: - to connect switch (exchange) with the external environment (subscriber)

i.e. it is the interface between subscribers and exchange.

1.3.3 COMPUTER UNIT:-

As the name specified it is the main part of the exchange that deals with the all

services provided by the exchange to the customers with the help of computer. It

also provides the updated data to all other part of the exchange.

The customers are using the services of the exchange by using the internet also

gets connected to the main server present this room via an internet room.

It mainly consists of the servers that are providing the different services.

IVRS is used for the change number services provided by the exchange.

CERS are provided by the exchange to avoid the problems that the users are

facing the repairing of telephone. In this system when the user enters its

complained it gets directly entered to the server and user is allotted with an id

number.

Local Directory Enquiry is another services provided by the exchange, by using

this; subscribers calls the particular number and gets the directory enquiry. The

server present in the main computer room provides this service.

Internet Directory Enquiry is the latest service by the exchange. In this type of

service makes it enquiry using the internet, which gets connected to the main

server at the internet room in the exchange and further to the main server in the

computer room.

1.3.4 POWER PLANT: - As we know that, the power is the main source or any

organization. It is the case of E-10B exchange. That is the first requirement of any

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organization is the input. The main source of this exchange is AC supply. Even if the

power supply gone off. Thus there must be adjustment source of power. The main parts of

the power room are:

Batteries: - these are the instant sources of the power as soon as power is gone off.

UPS (Uninterrupted Power Supply):- the UPS must give supply to the computer.

As we know there is some equipment which can withstand any type of power

supply, but there are also some instruments which cannot withstand with this type

of power supply, even a microsecond delay will cause the loss of data.

Charging- Discharging Unit: - the batteries we are using in the power room need

timely charging. As soon as the AC power supply is on, we make use of the

charging unit present in the power room. The slowly charging of the batteries is

known as the trickle charging. But sometimes we need the BOOSTER charging.

In this type of charging awe take of the batteries from the load and charge

separately, until it gets fully charged.

The main work of the discharging unit is to control the discharging of the

batteries.

Inverter and Converter Unit: - the main use of this system is to change AC mains

to DC and vice versa as required by the parts of exchange.

Engine Room:-we know that the batteries are the instant source of supply but we

cannot use it for much larger time, thus for this, we have an engine to generate the

power supply. They are of 885 KVA. Thus, this room controls the supply of the

engine.

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Fig. 1.2- Power Plant

1.3.5 CENTRAL AIR CONDITIONER: - For the function of electrical equipment,

cooling system is basic requirement. The basic advantages of cooling systems are

following-

It provides the thermal stability so that the temperature does not reach the

tolerance limit of electronic equipment

It saves equipment from dust so to avoid malfunction of equipment’s.

It protects equipment from excess humidity which can caused rusting of

equipment.

The basic unit of measurement used in the industry is known as “ton of

refrigeration” (TR) which is equivalent to the heat extracted in 24 hours for

converting thousands kg of liquid to ice at zero degree.

The compressor is the heart of the AC system and the costliest. It increases the

pressure and temperature of the refrigerant gas coming from the evaporator coils

by compressing it.

Compressor comes in various types. The most widely used is simple reciprocal

type a cylinder and piston arrangement. For capacity more than 120 TR,

centrifugal compressors are used. The condenser liquefies the refrigerant gas by a

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heat exchange process. The capillary tube or the expansion valve pressurizes

liquid refrigerant and meters it flows to the evaporator.

The refrigerant then passes through the evaporator coils, which extract heat out of

the ambience.

1.3.6 MAIN DISTRIBUTION FRAME: - The primary function of MDF is:

The fault of telephone number is removed in the MDF; it is called as Fault

Remove Section.

For removing the fault of telephone number, we use the testing

These testing are T.T.Y. testing, Group testing, etc.

For any type of testing firstly we need the vertical no. or the live tester, printer and

computer test N.E. number of that particular telephone number.

The telephone numbers are also disconnected in the MDF because of some

specific reason.

Parts of MDF:-

Horizontal side

Vertical side

Horizontal side: It is again subdivided in to two parts

Exchange side

Line side

Description of the horizontal side:-

RACK: - On the rack, the tags are situated. One rack is having eight tags. The

courting is done from up (0) to down (7).

TAG: - Each rack consists of eight tags.

1tag = 4 core

1 core = 4 bunch

1 bunch = 2 line

N.E.:- The word NE stands for the ‘NUMBER OF EQUIPMENT’. It is a 128 pair

cable. The EWSD and MDF connected by NE.

WEDGE:- If we want to disconnect any two numbers then we insert a wedge

between subscriber side and exchange side. Here wedge works as insulator made

of plastic.

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Vertical side: The vertical aside connected to the underground cable. This cable is

having 100 pairs. These pair is distributed when we allot the telephone number to the

subscriber. Vertical side is again subdivided in two parts that one part is connected

with the horizontal side and another with the subscriber line by using 100 pair

underground cable.

Fig. 1.3 MDF (MAIN DISTRIBUTION FRAME)

1.4 WLL (WIRE LESS FOR LOCAL LOOP):- A WLL provides solution to

face these difficulties better than the solution provided by wired loop technology. WLL

(Wireless in Local Loop) is an emerging Access Network technology based on CDMA

(Code Division Multiple Access) principle. This technology is very much useful for

providing cost effective mobile service, for providing wireless telephone connection in

areas where provision of land line telephone connection is not feasible. A WLL system

replaces the copper loop with radio frequency loop, maintaining the existing services of a

basic telephone system. Systems WLL is based on:

Cellular

Satellite (specific and adjunct)

Microcellular

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Due to drastic changes in internet, these services use the broadband local loop systems.

To deal this deal in the short term, the digital subscriber line (DSL)technologies,

including HDSL,ADSL and very high bit rate DSL(VDSL) is need to be developed. In

WLL system, entire coverage area is divided into a number of hexagonal sub-areas called

cells. But we get services in only one cell. E.g. BSNL is providing one cell area. But if

the WLL is based on CDMA then user can use all services of cellular system.eg in India,

Reliance, and Tata Indicom.

4.1.1 WLL SETUP: - WLL is a kind of radio system. Most of the WLL systems are

developed according to the standards for mobile systems. In terms of multiple access

(FDMA), the time division multiple access (TDMA) and code division multiple access

(CDMA). WLL provide a variety of data services and multimedia services as well as

voice.

Fig.-1.4 WLL (Wireless for Local Loop) SETUP

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1.4.2 WLL ARCHITECTURE: - In WLL architecture,

BSC (base station controller) is the heart of a WLL system. It interfaces with the

PSTN,BTS and a operation maintenance centre(OMC) to perform call processing,

voice coding etc.

BTS (base transceiver system) interface between the BSC and subscriber stations.

One BTS has an antenna power control functions, which may be unidirectional or

directional. It placed at the centre of the hexagonal cell and serves subscriber

within the cell.

FSU (fixed subscriber unit) is an interface between subscriber wired devices and

WLL network. The wired devices can be telephone and facsimile as well as

computers.

Fig.1.5- WLL (WIRELESS FOR LOCAL LOOP) ARCHITECTURE

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1.4.3 ADVANTAGES: - Country wide induction of WLL underway of areas than are

non-feasible for the normal network. Helping relieves congestion of connections in the

normal cable / wire based network in urban areas Limited the mobility without any

airtime charges. It has improved signal and reducing the interference Greater capacity

than mobile. Provides ease of operation, administration & maintenance at lower cost. The

telecommunication is the biggest factor in influencing the speed of life in the modern age.

Today we can get connection with any corner of world through the push button of

computer; with the small mobile phone we can send not only the messages but also the

secret document. As we know that there is positive view behind any mention that it

should be helpful in the development of society. But humans have diverted mentality

some of them of positive view and some of them of negative view. Where use any

invention for the welfare of society but some uses for the satisfaction their disturbed

mentality and to earn more and more money whether it may be harmful for the society.

They infringe the norms of society and their behavior is condemned as antisocial,

immoral and sinful.

The main advantages of WLL system includes:

Rapid installation.

Flexible Planning.

Less fault liabilities.

Cost effectiveness.

Copper saving. Suitable for congested area.

1.5 BROADBAND: - When the term “broadband” was initially introduced, it was

by differentiation from dial-up service, and was typified by two distinct characteristics:

speed and “always on.” The former was a coarse measure of capacity. The latter was a

definition of fundamentally different user experience: the experience of relatively

seamless integration into one's life—at least one's life at the desk—relative to the

prevailing experience that preceded it. Today's planning documents for the next

generation transition continue to reflect, in different measures, these two distinct

attributes of future networks. A review of broadband planning efforts suggests that there

is a broadly shared set of definitions and targets of policy, but some diversity of

emphasis. The primary distinction in emphasis is between a focus on high capacity and a

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focus on user experience, in particular on ubiquitous, seamless connectivity. We also

observe a secondary division, within the focus on high capacity, between a focus on

numeric measures of capacity, most prominently download speeds, and a focus on

applications supported. There is substantial overlap in practical policy terms between the

two goal definitions. Both would seek the highest capacity feasible within a time period.

There might, however, be subtle differences. For example, both would emphasize fiber to

the home infrastructure; but a high capacity focus might emphasize the theoretically

unlimited capacity of fiber, while a focus on user-centric experience might focus on the

relative symmetry of data carriage capacity, assuming that end-users have as much to give

as to receive.

1.6 FIBRE OPTICS:

Optical Fibre is new medium, in which information (voice, Data or Video) is transmitted

through a glass or plastic fibre, in the form of light, following the transmission sequence

give below:

(1) Information is encoded into electrical signals.

(2) Electrical signals are converted into light signals.

(3) Light travels down the fibre.

(4) A detector changes the light signals into electrical signals.

(5) Electrical signals are decoded into information.

1.6.1 ADVANTAGES OF FIBRE OPTICS:

Fibre Optics has the following advantages:

(I) Optical Fibres are non conductive (Dielectrics)

- Grounding and surge suppression not required.

- Cables can be all dielectric.

(II) Electromagnetic Immunity:

- Immune to electromagnetic interference (EMI)

- No radiated energy.

- Unauthorized tapping difficult.

(III) Large Bandwidth (> 5.0 GHz for 1 km length)

- Future upgradability.

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- Maximum utilization of cable right of way.

- One time cable installation costs.

(IV) Low Loss (5 dB/km to < 0.25 dB/km typical)

- Loss is low and same at all operating speeds within the fibre's

specified bandwidth long, unrepeated links (>70km is operation).

(v) Small, Light weight cables.

- Easy installation and Handling.

- Efficient use of space.

(vi) Available in Long lengths (> 12 kms)

- Less splice points.

(vii) Security

- Extremely difficult to tap a fibre as it does not radiate energy that

can be received by a nearby antenna.

- Highly secure transmission medium.

(viii) Security - Being a dielectric

- It cannot cause fire.

- Does not carry electricity.

- Can be run through hazardous areas.

(ix) Universal medium

- Serve all communication needs.

- Non-obsolescence.

1.6.2 APPLICATION OF FIBRE OPTICS IN COMMUNICATIONS:

- Common carrier nationwide networks.

- Telephone Inter-office Trunk lines.

- Customer premise communication networks.

- Undersea cables.

- High EMI areas (Power lines, Rails, Roads).

- Factory communication/ Automation.

- Control systems.

- Expensive environments.

- High lightening areas.

- Military applications.

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- Classified (secure) communications.

1.6.3 Transmission Sequence:

(1) Information is encoded into Electrical Signals.

(2) Electrical Signals are converted into light Signals.

(3) Light Travels down the Fiber.

(4) A Detector Changes the Light Signals into Electrical Signals.

(5) Electrical Signals are decoded into Information.

- Inexpensive light sources available.

- Repeater spacing increases along with operating speeds because low loss

fibres are used at high data rates.

Fig: Transmission Sequence

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1.6.4 PRINCIPLE OF OPERATION Principle of Operation – Theory:

Total Internal Reflection - The Reflection that Occurs when a Ligh Ray

Travelling in One Material Hits a Different Material and Reflects Back into

the Original Material without any Loss of Light.

1.6.5 FIBRE TYPES: The refractive Index profile describes the relation between the

indices of the core and cladding. Two main relationships exist:

(I) Step Index

(II) Graded Index

The step index fibre has a core with uniform index throughout. The profile shows a sharp

step at the junction of the core and cladding. In contrast, the graded index has a non-

uniform core. The Index is highest at the center and gradually decreases until it matches

with that of the cladding. There is no sharp break in indices between the core and the

cladding.

By this classification there are three types of fibres :

(I) Multimode Step Index fibre (Step Index fibre)

(II) Multimode graded Index fibre (Graded Index fibre)

(III) Single- Mode Step Index fibre (Single Mode Fibre)

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(1) STEP INDEX MULTIMODE FIBRE: This fibre is called "Step Index"

because the refractive index changes abruptly from cladding to core. The cladding has a

refractive index somewhat lower than the refractive index of the core glass. As a result, all

rays within a certain angle will be totally reflected at the core-cladding boundary. Rays

striking the boundary at angles grater than the critical angle will be partially reflected and

partially transmitted out through the boundary. After many such bounces the energy in

these rays will be lost from the fibre.

The paths along which the rays (modes) of this step index fibre travel differ,

depending on their angles relative to the axis. As a result, the different modes in a pulse

will arrive at the far end of the fibre at different times, resulting in pulse spreading which

limits the bit-rate of a digital signal which can be transmitted.

The maximum number of modes (N) depends on the core diameter (d),

wavelength and numerical aperture (NA)

x d x N A

N= 0.5 x (---------------------- ) 2

( )

This types of fibre results in considerable model dispersion, which results the fibre's band

width.

(2) GRADED INDEX MULTI-MODE FIBRE: This fibre is called graded index

because there are many changes in the refractive index with larger values towards the

center. As light travels faster in a lower index of refraction. So, the farther the light is from

the center axis, the grater is its speed. Each layer of the core refracts the light. Instead of

being sharply reflected as it is in a step index fibre, the light is now bent or continuously

refracted in an almost sinusoidal pattern. Those rays that follow the longest path by

travelling near the outside of the core, have a faster average velocity. The light travelling

near the center of the core has the slowest average velocity.

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As a result all rays tend to reach the end of the fibre at the same time. That causes

the end travel time of different rays to be nearly equal, even though they travel different

paths.

The graded index reduces model dispersing to 1ns/km or less.

Graded index fibres have core diameter of 50, 62.5 or 85 m and a cladding

diameter of 125 m. The fibre is used in applications requiring wide bandwidth low

model dispersion. The number of modes in the fibre is about half that of step index fibre

having the same diameter & NA.

High orderMode

Dispersion RefractiveIndex Profile

Low Order ModeMulti mode Step Index

InputPulse

OutputPulse

n1

n2

Single Mode Step Index

n1n2

Single Mode Step Index

n1n2

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Dispersion

Multi mode Graded Index

n1

n2

dxNA

N= 0.25 x ( ---------------- )2

()

(3) SINGLE MODE FIBRE: Another way to reduce model dispersion is to reduce

the core's diameter, until the fibre only propagates one mode efficiently. The single mode

fibre has an exceedingly small core diameter of only 5 to 10 m. Standard cladding

diameter is 125 m. Since this fibre carries only one mode, model dispersion does not

exists. Single mode fibres easily have a potential bandwidth of 50to 100GHz-km.

The core diameter is so small that the splicing technique and measuring technique are

more difficult. High sources must have very narrow spectral width and they must be very

small and bright in order to permit efficient coupling into the very small core dia of these

fibres.

One advantage of single mode fibre is that once they are installed, the system's

capacity can be increased as newer, higher capacity transmission system becomes

available. This capability saves the high cost of installing a new transmission medium to

obtain increased performance and allows cost effective increases from low capacity

system to higher capacity system.

As the wavelength is increased the fibre carries fewer and fewer modes until only one

remains. Single mode operation begins when the wavelength approaches the core

diameter. At 1300 nm, the fibre permits only one mode it becomes a single mode fibre.

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As optical energy in a single mode fibre travels in the cladding as well as in the core,

therefore the cladding must be a more efficient carrier of energy. In a multimode fibre

cladding modes are not desirable a cladding with in efficient transmission characteristic

can be tolerated. The diameter of the light appearing at the end of the single mode fibre is

larger than the core diameter, because some of the optical energy of the mode travels in

the cladding. Mode field diameter is the term used to define this diameter of optical

energy.

1.6.6 OPTICAL FIBRE PARAMETERS:

Optical fibre systems have the following parameters.

(I) Wavelength.

(II) Frequency.

(III) Window.

(IV) Attenuation.

(V) Dispersion.

(VI) Bandwidth.

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Chapter -2

GLOBAL SYSTEM FOR MOBILE

2.1 INTRODUCTION:- Global System for Mobile (GSM) is a second generation

cellular standard developed to cater voice services and data delivery using digital

modulation. These are main point of GSM.

Early 80’s Europe was experiencing rapid growth in the analog cellular telephone

systems.

1982 Conference of European Posts and Telegraphs (CEPT) GSM (Group Special

Mobile) group was formed to study and develop a pan-European public land

mobile system.

GSM mandate was to develop a standard to be common for the countries that

created it – provide service to the entire European continent.

GSM criteria –

Good subjective speech quality

Low terminal and service cost

Support for international roaming – one system for all of Europe

Ability to support handheld terminals

Support for range of new services and facilities

Enhanced Features

ISDN compatibility

Enhance privacy

Security against fraud

Today many providers all over the world use GSM (more than 135 countries)

More than 1300 million subscribers in world and 45 million subscribers in India.

2.2 SUPPLEMENTARY SERVICES:-

Call Waiting- Notification of an incoming call while on the handset

Call Hold- Put a caller on hold to take another call

Call Barring- All calls, outgoing calls, or incoming calls

Call Forwarding- Calls can be sent to various numbers defined by the user

Multi Party Call Conferencing - Link multiple calls together

CLIP – Caller line identification presentation

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CLIR – Caller line identification restriction

CUG – Closed user group

2.3 GSM SPECIFICATION:-

Carrier Separation 200 KHz

Duplex Distance 45 MHz

No. of RF carriers 124

Access Method TDMA/FDMA

Modulation Method GMSK

Modulation data rate 270.833 Kbps

Table 2.2 - GSM SPECIFICATION

2.4 GSM FREQUENCES: -

GSM 900

Mobile to BTS (uplink): 890-915 MHz

BTS to Mobile (downlink):935-960 MHz

Bandwidth: 2* 25 MHz

GSM 1800

Mobile to BTS (uplink): 1710-1785 MHz

BTS to Mobile (downlink) 1805-1880 MHz

Bandwidth: 2* 75 MHz

2.5 GSM SYSTEM ARCHITECTURE: - these are parts of GSM system

Mobile Station (MS)

Mobile Equipment (ME)

Subscriber Identity Module (SIM)

Base Station Subsystem (BSS)

Base Transceiver Station (BTS)

Base Station Controller (BSC)

Network Switching Subsystem(NSS)

Mobile Switching Center (MSC)

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Home Location Register (HLR)

Visitor Location Register (VLR)

Authentication Center (AUC)

Equipment Identity Register (EIR)

Figure: - 2.1 GSM SYSTEM ARCHITECTURE

2.5.1 MOBILE SUBSYSTEM (MS):- The Mobile Station is made up of two entities –

1. Mobile Equipment (ME)

2. Subscriber Identity Module (SIM)

Mobile Equipment:-

Portable, vehicle mounted, hand held device

Uniquely identified by an IMEI (International Mobile Equipment Identity)

Voice and data transmission

Monitoring power and signal quality of surrounding cells for optimum handover

Power level : 0.8W – 20 W

160 character long SMS.

Subscriber Identity Module (SIM):-

Smart card contains the International Mobile Subscriber Identity (IMSI).

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Allows user to send and receive calls and receive other subscribed services.

Encoded network identification details.

- Key Ki, Kc and A3,A5 and A8 algorithms.

Protected by a password or PIN.

Can be moved from phone to phone – contains key information to activate the

phone.

2.5.2 BASE SWITCHING SUBSYSTEM (BSS):- Base Station Subsystem is

composed of two parts that communicate across the standardized Abis interface allowing

operation between components made by different suppliers

1. Base Transceiver Station (BTS)

2. Base Station Controller (BSC)

Base Transceiver Station (BTS) :-

Encodes, encrypts, multiplexes, modulates and feeds the RF signals to the

antenna.

Frequency hopping

Communicates with Mobile station and BSC

Consists of Transceivers (TRX) units

Base Station Controller (BSC) :-

Manages Radio resources for BTS

Assigns Frequency and time slots for all MS’s in its area

Handles call set up

Trans coding and rate adaptation functionality

Handover for each MS

Radio Power control

It communicates with MSC and BTS

2.5.3 NETWORK SWITCHING SUBSYSTEM (NSS):- The NSS is made up of five

entities –

1. Mobile Switching Center (MSC)

2. Home Location Register (HLR)

3. Visitor Location Register (VLR)

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4. Authentication Center (AUC)

5. Equipment Identity Register (EIR)

Mobile Switching Subsystem (MSC) :-

Heart of the network

Switch speech and data connections between:

Base Station Controllers

Mobile Switching Centers

GSM-networks

Other external networks

Three main jobs:

1) connects calls from sender to receiver

2) collects details of the calls made and received

3) supervises operation of the rest of the network components

Manages communication between GSM and other networks

Call setup function and basic switching

Call routing

Billing information and collection

Mobility management

Registration

Location Updating

Inter BSS and inter MSC call handoff

MSC does gateway function while its customer roams to other network by

using HLR/VLR.

Home Location Register (HLR) :-

permanent database about mobile subscribers in a large service area(generally

one per GSM network operator)

Database contains IMSI, prepaid/postpaid, roaming restrictions,

supplementary services.

contains administrative information of each subscriber

current location of the mobile

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Visitor Location Register (VLR) : -

Temporary database which updates whenever new MS enters its area, by

HLR database.

Controls those mobiles roaming in its area.

Reduces number of queries to HLR.

Database contains IMSI, TMSI, MSRN, Location Area, authentication key.

tracks which customers have the phone on and ready to receive a call.

periodically updates the database on which phones are turned on and ready to

receive calls.

Authentication Center (AUC) : -

Mainly used for security.

Data storage location and functional part of the network.

Protects against intruders in air interface.

Maintains authentication keys and algorithms and provides security triplets

(RAND, SRES, Kc)

Generally associated with HLR.

Equipment Identity Register (EIR) : -

Database that is used to track handsets using the IMEI (International Mobile

Equipment Identity).

Made up of three sub-classes: The White List, The Black List and the Gray

List.

Optional database.

Only one EIR per PLMN.

2.6 ADVANTAGE OF GSM: -

Crisper, cleaner quieter calls.

Security against fraud and eavesdropping

International roaming capability in over 100 countries

Improved battery life

Efficient network design for less expensive system expansion

Efficient use of spectrum

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Advanced features such as short messaging and caller ID

A wide variety of handsets and accessories

High stability mobile fax and data at up to 9600 baud

Ease of use with over the air activation, and all account information is held in a

smart card which can be moved from handset to handset

2.7 GSM APPLICATION: -

Mobile telephony

GSM-R

Telemetry System

- Fleet management

- Automatic meter reading

- Toll Collection

- Remote control and fault reporting of DG sets

Value Added Services

2.8 FUTURE OF GSM: -

2nd Generation

GSM -9.6 Kbps (data rate)

2.5 Generation ( Future of GSM)

HSCSD (High Speed ckt Switched data)

Data rate : 76.8 Kbps (9.6 x 8 kbps)

GPRS (General Packet Radio service)

Data rate: 14.4 - 115.2 Kbps

EDGE (Enhanced data rate for GSM Evolution)

Data rate: 547.2 Kbps (max)

3 Generation

WCDMA(Wide band CDMA)

Data rate : 0.348 – 2.0 Mbps

CONCLUSION:-

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The whole conversation says only one thing that the BSNL will give a big benefit

in future.

It will change the communication world and thinking of consumer.

It will also give many benefits of other networks like vodaphone, idea etc.

The advantage yields faster, cheaper.

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REFERENCES:-

www.bsnl.co.in

www.telecomtalk.info.com

www.slideworld.com

www.powerpointpresentation.com

www.seminarreport.com

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