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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