BHARAT SANCHAR NIGAM LIMITED
Submitted for the partial fulfillment for
the award of the degree of
BACHELOR OF TECHNOLOGY
RAJASTHAN TECHNICAL UNIVERSITY, KOTA
VII SEM (ECE)
Department of Electronics & Communication
ENGINEERING COLLEGE AJMER
(An Autonomous Institute of Govt. of Rajasthan)
Badliya Chouraha,N.H. 8,By-Pass,Ajmer-305002
Website : www.ecajmer.ac.in ,Ph no. 0145-2671773,776,800,801
It is with profound gratitude that I express my deep indebtedness to all the employees
of B.S.N.L. without whose support and guidance it would not have been possible for
this training to have materialized and taken a concrete shape. I owe my personal
thanks to my trainers in charge – Dr. S.l. verma (SDE), and Dr. Sandeep saini
(JTO) who extended full support and co-operation at every stage of my training
period. I would also like to take this opportunity to acknowledge the guidance from
Mr. Dhirender mathur (HOD of electronics and communication) and Mrs.
Rekha mehra (Seminar Co-ordinator of electronics and communication) for
undergoing training at a reputed company like B.S.N.L.
I am also indebted to my parents and friends for their constant encouragement and
helping me in my endeavor.Last, but not the least, I would like to thank everyone who
has contributed for the successful completion of my training.
(B.TECH VII SEMESTER - ECE)
Organizations are made up of people and function through people. Without people,
organizations cannot exist. The resources of men, money, material, machinery, and
mechanism are connected, coordinated and utilized through people. Engineers need to
concentrate more on mechanism and the way in which things have been made. The
need of training arises for doing things yourself, understanding its way.
Practical exposure for doing things makes a person conversant to the technicalities
involved in any job. In view of such benefits, imparting of vocational training has
been made an integral part of any academic structure.
In B.S.N.L., training is given to Engineering Aspirants to secure future in the dynamic
world of telecommunications. Today telecommunication industry is one of the very
fastest growing industries in the world.
In this order I have taken 28 days BSNL training. In my report I try to introduce
Leased line concepts, WIMAX, Wi-Fi, optical fiber concepts and overview of
INTRODUCTION TO BSNL
India is the fourth largest telecom market in Asia after China, Japan and South Korea.
The Indian telecom network is the eighth largest in the world.
TYPE: COMMUNICATION SERVICE PROVIDER
AVAILABLITY: NATIONAL EXCEPT DELHI & MUMBAI
OWNER: THE GOVERNMENT OF INDIA
1.1 HOW BSNL CAME IN TELECOM MARKET:
The initial phase of telecom reforms began in 1984 with the creation of Center for
Department of Telematics (C-DOT) for developing indigenous technologies and
private manufacturing of customer premise equipment. Soon after, the Mahanagar
Telephone Nigam Limited (MTNL) and Videsh Sanchar Nigam Limited (VSNL)
were set up in 1986.The Telecom Commission was established in 1989. A crucial
aspect of the institutional reform of the Indian telecom sector was setting up of an
independent regulatory body in 1997 – the Telecom Regulatory Authority of India
(TRAI), to assure investors that the sector would be regulated in a balanced and fair
manner. In 2000, DoT corporatized its services wing and created Bharat Sanchar
1.2 INSTITUTIONAL FRAMEWORK:
It is defined as the system of formal laws, regulations, and procedures, and informal
conventions, customs, and norms, that broaden, mold, and restrain socio-economic
activity and behavior. The country has been divided into units called Circles, Metro
Districts, Secondary Switching Areas (SSA), Long Distance Charging Area (LDCA)
and Short Distance Charging Area (SDCA).
In India, DoT is the nodal agency for taking care of telecom sector on behalf of
Its basic functions are:
• Policy Formulation
• Review of performance
• Wireless spectrum management
• Administrative monitoring of PSUs
• Research & Development
• Standardization/Validation of Equipment
1.3 BSNL CONTRIBUTION TO DEVELOPMENT OF TELECOM:
Bharat Sanchar Nigam Limited was formed in year 2000 and took over the service
providers role from DOT. BSNL’s roadmap for providing customer with access to the
latest telecommunications services without losing sight of universal service access has
been by way of utilizing optimally the existing infrastructure and accelerating
advances in technological component by innovative absorption.
ACHIEVEMENTS OF BSNL:
• BSNL has a customer base of over 9 crore and is the fourth largest integrated
telecom operator in the country.
• BSNL is the market leader in Broadband, landline and national transmission
• BSNL is also the only operator covering over 5 lakh village with telecom
• Area of operation of BSNL is all India except Delhi & Mumbai.
WORKING OF BASIC TELECOMMUNICATION NETWORK
This section includes brief introduction of how a call is processed when we dial a call
from basic telephone to another basic telephone or from basic to mobile or vice versa.
2.1 CALL SETUP:
• When a subscriber calls to another subscriber first its request goes to the nearest
switching centre that is PSTN (Public Switching Telecommunication Network).
Then it processes the caller and subscriber’s number if it exists in the same BSC
then call setup is completed.
• If subscriber is not in the same BSC (Base Switching Centre) then call transfer to
MSC (Main Switching Centre) then it transfers the call to prior BSC then call
setup is completed.
• If Caller calls to a mobile subscriber then call transfer is done by MTSO now call
transfer is done on BTSs (Base Transceiver Station) and call setup is completed.
FIG 2.1 HOW LINE REACHES FROM SUBSCRIBER TO EXCHANGE
FUNCTION OF EXCHANGE:
• Exchange of information with subscriber lines with other exchange. This is done
by two type of signaling:
1. Inchannel signaling
2. Common channel signaling
• Processing of signaling information and controlling the operation of signaling
• Charging and billing.
2.2 ELECTRONIC EXCHANGE:
• All control functions by series of instructions are stored in memory.
• Memories are modifiable and control program can always be rewritten. For each
call processing step decision is taken according to class of service.
2.3 CARRIER ROOM:
Leased line connectivity is provided in carrier room. This room has two parts:
1. Conventional leased line system
2.3.1 CONVENTIONAL LEASED LINE SYSTEM:
• It consists of modems and routers that are provided by the company requesting for
• Connectivity of different ATM, banks etc. is provided by BSNL here.
• For this, we have 4 modems (2 in Exchange, 1 at sender and 1 at receiver)
• Modems are used for short distances i.e. trans and receive part are received here
and local lead connection is given to the subscriber.
• Local lead faults can be handled here but the trans and receive faults can be
handled by the department meant for it.
• Accept 64Kbps or 2 Mbps.
• For long distance communication we have MUXS and data is sent through optical
fibers. MUXS are present at both the ends.
2.3.2 MANAGED LEASED LINE NETWORK:
• No open wiring.
• Route can be changed by the computer software
• In Agra Gate Exchange, we have 3 VMUX of type II.
2.4 MDF(MAIN DISTRIBUTION FRAME):
M.D.F. is a media between switching network and subscriber’s line. It is a termination
point within the local telephone exchange where exchange equipment and
terminations of local loops are connected by jumper wires.
FIG 2.2 MDF
2.4.1 FUNCTIONS OF MDF:
• All cable copper wires supplying services through user telephone lines are
terminated and distributed through MDF.
• The most common kind of large MDF is a long steel rack accessible from both
sides. Each jumper is a twisted wire.
• It consists of local connection and broadband connection frames for the main
• The MDF usually holds central office protective devices including heat coils and
functions as a test point between a line and the office.
• It provides testing of calls.
• It checks whether fault is indoor or external.
• All lines terminate individually.
2.5 POWER PLANT:
• It provides -48V to the switch rooms and 48V to the connections.
• Batteries are artificially discharged once in a year for their maintenance.
• Cooling is provided through fans & AC.
• There is earth region too for protection.
A leased line (dedicated line) is a permanent fiber optic or telephone connection
between two points set up by a telecommunications carrier. They can be used for
telephone, data, or Internet services. Businesses use a leased line to connect to
geographically distant offices because it guarantees bandwidth for network traffic. For
example, a bank may use a leased line in order to easily transfer financial information
from one office to another. Customers generally pay a flat monthly rate for the service
depending on the distance between the two points. Leased lines do not have telephone
numbers. The information sent through the leased line travels along dedicated secure
channels, eliminating the congestion that occurs in shared networks.
3.2 DRAWBACKS OF TRADITIONAL LEASED LINE CIRCUITS:
1. Limited range of services - Only Plain Leased Line Service, Data cards
support only up to 64 kbps, no support for N x 64 Kbps.
2. From Operator point of view in case of Leased Line Circuit different boxes
from different vendors so difficult to manage & control.
3. No Centralized Monitoring or alarm or performance monitoring.
The solution to this is MLLN.
3.3 MLLN ( MANAGED LEASED LINE NETWORK ):
The MLLN service is specially designed mainly for having effective control and
monitoring on the leased line so that the down time is minimized and the circuit
efficiency is increased. This mainly deals with data circuits ranging from 64 Kbps to
3.3.1 MLLN FEATURES:
1. MLLN is an integrated, fully managed, multi service digital network platform
through which service provider can offer a wide range of service at an optimal
cost to business subscriber.
2. Using NMS, MLLN can provide high speed Leased Line with improved QoS,
high availability & reliability.
3. Except for connecting the local lead to the MODEM all operations &
maintenance is carried out through ROT (Remote Operating Terminal).
4. NMS supports service provisioning, Network optimization, planning & service
5. System offers end to end circuit creation and modification, circuit loop testing &
fault isolation, automatic rerouting of traffic in case of trunk failure, software
programmability of NTU etc.
6. Banking, Financial institution, Stock market, paper industry, broadcasting &
Internet service Provider are the main customers for MLLN.
3.3.2 MLLN ADVANTAGES:
1. 24 hrs Performance Monitoring of the circuit.
2. Circuit fault reports generated proactively.
3. On Demand the Bandwidth can be increased.
4. Low lead time for new circuit provisioning.
5. Protection against the failure of the circuit through recovery Management
process either automatic or manually.
6. Long drive on single copper pair.( for 64 kbps – 7 kms & for 2mbps – 3.5 kms)
7. Centrally managed from ROT connected to the NMS.
3.3.3 APPLICATION OF MLLN:
1. Corporate high speed internet access through Broadband.
2. LAN interconnection.
3. Hotline connectivity for voice.
4. Point to point connection for data circuit.
5. Point to multipoint connection.
• Smaller private version of Internet. It uses Internet protocols to create
enterprise-wide network which may consists of interconnected LANs.
• It may or may not include connection to Internet.
• Intranet is an internal information system based on Internet technology and web
protocols for implementation within a corporate organization.
• This implementation is performed in such a way as to transparently deliver the
immense informational resources of an organization to each individual’s desktop
with minimal cost, time and effort.
• The Intranet defines your organization and displays it for everyone to see.
4.2 FEATURES OF INTRANET:
1. It is scalable.
2. It is Interchangeable.
3. It is platform independent
4. It is Hardware independent.
5. It is vendor independent.
4.3 WHY INTRANET FOR AN ORGANIZATION:
• Quick access to voice, video, data and other resources needed by users.
• Variety of valuable Intranet applications improves communication and
productivity across all areas of an enterprise.
• A 21st Century Telephone.
• An ISO Tool.
• A Target Marketing Tool.
• A Decision Making Tool.
• A Complete Communication Tool.
FIG 4.1 INTRANET NETWORK (REF- 5)
4.4 APPLICATIONS OF INTRANET:
• Publishing Corporate documents.
• Access into searchable directories.
• Excellent Mailing Facilities.
• Proper Sharing of Information.
• Developing Groupware Applications.
4.5 TECHNICAL OVERVIEW OF THE INTRANET TECHNOLOGY
Intranet runs on open TCP/IP network, enable companies to employ the same type of
servers and browser used for World Wide Web for internal applications distributed
over the corporate LAN.
A typical Intranet implementation involves a high end machine called a server which
can be accessed by individual PCs commonly referred to as clients, through the
The Intranet site setup can be quite inexpensive, especially if your users are already
connected by LAN.
4.6 INTRANET APPLICATIONS IN A CIRCLE:
Every circle must have an intranet server which should have the following:
• All posting/transfer/relieving orders issued within circle to be hosted on the
• All letters circulars/letters issued from different sections of the circle office to be
hosted on the server for immediate access by SSAs. Each section in circle office
Administration, Operations, Marketing, Finance, Planning, Computers etc can
have web pages hosted on the server.
• A database can be maintained for MIS reports and all other reports to be sent
periodically by SSAs to circle office. The database can have front end forms
designed in ASP or PHP for the SSAs to input the data. Separate programs can be
developed to consolidate the data fed by SSAs.
• All data prepared and /or distributed during SSA heads meetings can be hosted
on the Intranet.
• The implementation of the above will reduce the usage of paper and also reduce
the usage of FAX.
A corporate network (CN) is a closed and private computer network that affords
secure communications between geographically dispersed LANs of an enterprise.
• Socially oriented
• Had geographical boundaries
• Were expertise specific
• No access to corporate
• Not self sufficient
• Not self sustainable
• No corporate governance
An ideal network
• Business oriented
• International infrastructure &
• Comprehensive expertise
• Access to substantial corporate
• self sufficient
• Self sustainable
• Governed by strict values and
TABLE 5.1 DIFFERERCES BETWEEN TRADITIONAL AND IDEAL
NETWORKS (REF- 2)
The requirement in a Corporate Network is same as ideal network.
5.2 WHY DO BUISNESSES HAVE CORPORATE NETWORK?
A business implements a corporate network to share applications and data between
different computing devices and users in different locations. Unless the application is
web based or database driven, this usually means copying files back and forth
between a network drive and a local computer, where a desktop application is used to
read and/or edit the files.
The increasing need to access corporate data from anywhere has led to changes in the
nature of applications, in current model of corporate network.
A typical corporate network has the following characteristics:
• Many LAN segments.
• More than one network protocol (IP or IPX).
• OSPF-configured areas, if it uses IP.
• Dial-up connectivity for users connecting from home or while traveling.
• Connectivity to external networks.
• Demand-dial connections to branch offices.
• Dedicated circuits to branch offices.
• A corporate network typically uses different types of network media. The
different office segments can be on 10-MB Ethernet or Token Ring networks,
but the backbone network used for connecting the different networks and
hosting servers is usually made up of 100-MB Ethernet . Connectivity to
external networks (the Internet) is over leased lines. Connectivity to branch
offices is either over dial-up line or dedicated media (leased lines).
FIG 5.1 CORPORATE NETWORK (REF- 5)
5.3 FEATURES OF CORPORATE NETWORK SECURITY:
• Complete bullet-proof protection of the remote computers you have on your
• Executable patches can be easily uploaded to all your remote computers and
• Easy and intuitive configuration without lots of complicated configuration files.
Everything is configured through the stand-alone GUI interface from any
location where TCP/IP connection to your corporate network can be established.
• You do not need to physically visit your workstations when you need to change
security settings or install patches.
• The remote client service application is bullet-proof. Your users will not be able
to disable, uninstall or delete it.
• All traffic between the server and the clients is encrypted. All local files are
encrypted as well.
• The server service application and the remote client service application work as
NT services under Windows NT/2000/XP and higher therefore they will keep
working in the logoff mode.
WI-FI (WIRELESS FIDELITY)
6.1 WI-FI NETWORK:
A Wi-Fi network provides the features and benefits of traditional LAN technologies
such as Ethernet and Token Ring without the limitations of wires or cables. It
provides the final few meters of connectivity between a wired network and the mobile
user. WIFI is a wireless LAN Technology to deliver wireless broad band speeds up to
54 Mbps to Laptops, PCs, PDAs, dual mode Wi-Fi enabled phones etc.
6.2 WORKING OF WI-FI NETWORK:
In a typical Wi-Fi configuration, a transmitter/receiver (transceiver) device, called the
Access Point (AP), connects to the wired network from a fixed location using
standard cabling. A wireless Access Point combines router and bridging functions, it
bridges network traffic, usually from Ethernet to the airwaves, where it routes to
computers with wireless adapters. The AP can reside at any node of the wired
network and acts as a gateway for wireless data to be routed onto the wired network.
It supports only 10 to 30 mobile devices per Access Point (AP) depending on the
network traffic. Like a cellular system, the Wi-Fi is capable of roaming from the AP
and re-connecting to the network through another AP. Like a cellular phone system,
the wireless LAN is capable of roaming from the AP and re-connecting to the network
through other APs residing at other points on the wired network. This can allow the
wired LAN to be extended to cover a much larger area than the existing coverage by
the use of multiple APs such as in a campus environment. It may be used as a
standalone network anywhere to link multiple computers together without having to
build or extend a wired network.
FIG 6.1WI-FI NETWORK (REF- 5)
End users access the Wi-Fi network through Wi-Fi adapters, which are implemented
as cards in desktop computers, or integrated within hand-held computers. Wi-Fi
wireless LAN adapters provide an interface between the client Network Operating
System (NOS) and the airwaves via an antenna.
6.3 BENEFITS OF WI-FI:
Wi-Fi offers the following productivity, conveniences, and cost advantages over
traditional wired networks:
• Mobility: Wi-Fi systems can provide LAN users with access to real-time
information anywhere in their organization.
• Installation Speed and Simplicity: Installing a Wi-Fi system can be fast and easy
and can eliminate the need to pull cable through walls and ceilings.
• Installation Flexibility: Wireless technology allows the network to go where
wire cannot go.
• Reduced Cost-of-Ownership: While the initial investment required for Wi-Fi
hardware can be higher than the cost of wired LAN hardware, overall
installation expenses and life-cycle costs can be significantly lower.
• Scalability: Wi-Fi systems can be configured in a variety of topologies to meet
the needs of specific applications and installations. Configurations are easily
changed and range from peer-to-peer networks suitable for a small number of
users to full infrastructure networks of thousands of users that allows roaming
over a broad area.
• It offers much high speed up to 54 Mbps which is very much greater than other
wireless access technologies like CORDECT, GSM and CDMA.
6.4 LIMITATIONS OF WI-FI:
• Coverage: A single Access Point can cover, at best, a radius of only about 60
meters. For 10 square kms area roughly 650 Access Points are required, where
as CDMA 2000 1xEV-DO requires just 09 sites.
• Roaming: It lacks roaming between different networks hence wide spread
coverage by one service provider is not possible, which is the key to success of
• Backhaul: Backhaul directly affects data rate service. Wi-Fi real world data
rates are at least half of the their theoretical peak rates due to factors such as
signal strength, interference and radio overhead .Backhaul reduces the
remaining throughput further.
• Interference: Wi-Fi uses unlicensed spectrum, which mean no regulator recourse
against interference. The most popular type of Wi-Fi, ‘802.11’b uses.
7.1 WIRELESS BROADBAND SERVICES:
There are two fundamentally different types of broadband wireless services. The first
type attempts to provide a set of services similar to that of the traditional fixed-line
broadband but using wireless as the medium of transmission. This type, called fixed
wireless broadband, can be thought of as a competitive alternative to DSL or cable
modem. The second type of broadband wireless, called mobile broadband, offers the
additional functionality of portability, nomadicity and mobility.
WI-MAX is an acronym that stands for World-wide Interoperability for
Microwave Access and this technology is designed to accommodate both fixed and
mobile broadband applications.
7.2 SALIENT FEATURES OF WIMAX:
• OFDM-based physical layer.
• Very high peak data rates.
• Scalable bandwidth and data rate support.
• Adaptive modulation and coding (AMC).
• Link-layer retransmissions.
• Support for TDD and FDD OFDMA.
• Flexible and dynamic per user resource allocation.
• Support for advanced antenna techniques.
• Quality-of-service support.
• Robust security.
• Support for mobility.
• IP-based architecture.
7.3 EVOLUTION OF BROADBAND WIRELESS:
1. NARROWBAND WIRELESS LOCAL-LOOP SYSTEMS: The first application
for which a wireless alternative was developed and deployed was voice telephony.
These systems, called wireless local-loop (WLL). WLL systems based on the digital-
enhanced cordless telephony (DECT) and code division multiple access (CDMA)
standards continue to be deployed in these markets. During the same time, several
small start-up companies focused solely on providing Internet-access services using
wireless, antennas to be installed at the customer premises. These early systems
typically offered speeds up to a few hundred kilobits per second. Later evolutions of
license-exempt systems were able to provide higher speeds.
2. FIRST-GENERATION BROADBAND SYSTEMS: As DSL and cable modems
began to be deployed, wireless systems had to evolve to support much higher speeds
to be competitive. Very high speed systems, called local multipoint distribution
systems (LMDS), supporting up to several hundreds of megabits per second, were
In the late 1990s, one of the more important deployments of wireless broadband
happened in the so-called multi channel multipoint distribution services (MMDS)
band at 2.5GHz. The MMDS band was historically used to provide wireless cable
broadcast video services, especially in rural areas where cable TV services were not
available. The first generations of these fixed broadband wireless solutions were
deployed using the same towers that served wireless cable subscribers. These towers
were typically several hundred feet tall and enabled LOS coverage to distances up to
35 miles, using high-power transmitter.
The advent of satellite TV ruined the wireless cable business, and operators were
looking for alternative ways to use this spectrum. A few operators began to offer one-
way wireless Internet-access service, using telephone line as the return path.
3. SECOND - GENERATION BROADBAND SYSTEMS: Second-generation
broadband wireless systems were able to overcome the LOS issue and to provide
more capacity. This was done through the use of a cellular architecture and
implementation of advanced-signal processing techniques to improve the link and
system performance under multi path conditions. Many solved the NLOS problem by
using such techniques as orthogonal frequency division multiplexing (OFDM), code
division multiple access (CDMA), and multi antenna processing.
4. WIMAX AND OTHER BROADBAND WIRELESS TECHNOLOGIES:
WIMAX is not the only solution for delivering broadband wireless services. WiMAX
occupies a somewhat middle ground between Wi-Fi and 3G technologies when
compared in the key dimensions of data rate, coverage, QoS, mobility, and price.
7.3 WIMAX NETWORK ARCHITECTURE:
The overall network may be logically divided into three parts:
1. Mobile Stations (MS) used by the end user to access the network.
2. The access service network (ASN), which comprises one or more base stations
and one or more ASN gateways that form the radio access network at the edge.
3. Connectivity service network (CSN), which provides IP connectivity and all the
IP core network functions.
ASN-ACCESS SERVICES NETWORK
NAP-NETWORK ACCESS PROVIDER
CSN- CORE SERVICES NETWORK
NSP- NETWORK SERVICES PROVIDER
BS- BAS STATION
AAA-AUTHENTICATION AUTHONZATION & ACCOUNTING
FIG 7.1 WIMAX NETWORK ARCHITECTURE (REF- 3)
BASE STATION (BS): The BS is responsible for providing the air interface to the
MSS. Additional functions that may be part of the BS are micro mobility management
functions, such as handoff triggering and tunnel establishment, radio resource
management, QoS policy enforcement, traffic classification, DHCP (Dynamic Host
Control Protocol) proxy, key management, session management, and multicast group
ACCESS SERVICE NETWORK GATEWAY (ASN-GW): The ASN gateway
typically acts as a layer 2 traffic aggregation points within an ASN. Additional
functions that may be part of the ASN gateway include intra-ASN location
management and paging, radio resource management and admission control, caching
of subscriber profiles and encryption keys, AAA client functionality, establishment
and management of mobility tunnel with base stations, QoS and policy enforcement,
and foreign agent functionality for mobile IP, and routing to the selected CSN.
CONNECTIVITY SERVICE NETWORK (CSN): The CSN provides connectivity
to the Internet, ASP, other public networks, and corporate networks. The CSN is
owned by the NSP and includes AAA servers that support authentication for the
devices, users, and specific services. The CSN also provides per user policy
management of QoS and security. The CSN is also responsible for IP address
management, support for roaming between different NSPs, location management
between ASNs, and mobility and roaming between ASNs, subscriber billing and inter
operator settlement, inter-CSN tunneling to support roaming between different NSPs.
REFERENCE POINTS: The WiMAX NWG defines a reference point as a
conceptual link that connects two groups of functions that reside in different
functional entities of the ASN, CSN or MS. Reference points may not be a physical
interface except when the functional entities on either side of it are implemented on
different physical devices.
Reference point End points Description
R1 MS and CSN Implements the air interface (IEEE
R2 MS and CSN For authentication, authorization, IP host
configuration management and mobility
management, only a logical interface
between MS and CSN
R3 ASN and CSN Supports AAA, policy enforcement,and
mobility mgmt. capabilities
R4 ASN and ASN A set of protocols originating/terminating
in various entities within the ASN. In
Release I , R4 is the only interoperable
interface between different ASNs or
R5 CSN and CSN A set of protocols for interworking
between home and visited network.
R6 BS and ASN-GW A set of control and bearer plane
protocols for communication between BS
and ASN-GW. It may serve as a conduit
for exchange of different MAC states
information between neighboring BSs.
An optional set of control plane protocols
for co-ordination between two group of
functions identified in R6.
R8 BS and BS A set of control plane message flows and
bearer plane data flows between BSs to
ensure fast and seamless handover.
TABLE 7.1 REFERENCE POINTS (REF- 2)
GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM)
In wireless communication every region is divided into cells. Cell size is constant for
whole system. GSM is a form of multiplexing, which divides the available
bandwidth among the different channels. Most of the times the multiplexing
used is either TDM (Time division multiplexing) or FDM (Frequency Division
Multiplexing). SM differs from its predecessor technologies in that both
signaling and speech channels are digital, and thus GSM is considered a second
generation (2G) mobile phone system.
FIG 8.1 (REF- 4)
8.1 MAIN FEATURES OF GSM:
• Support for voice and data services
• Better frequency efficiency, smaller cells and more customers per cell
• High audio quality and reliability for wireless, uninterrupted phone calls at higher
speeds (e.g. from cars, trains) i.e. high transmission quality.
• Authentication via chip-card and PIN.
• Worldwide connectivity.
8.2 GSM SUBSYSTEMS:
• RADIO SUBSYSTEM (RSS)
• NETWORK AND SWITCHING SUBSYSTEM (NSS)
8.2.1 RADIO SUBSYSTEM:
MOBILE STATION (MS):
A mobile unit is a transmitter as well as receiver too. It has a SIM (Subscriber Identity
Module) which gives a unique identity of a subscriber. Every mobile unit has a unique
IMIE (International Mobile Equipment Identity) number.
BASE TRANSCEIVER STATION (BTS):
• A base transceiver station or cell site (BTS) is a piece of equipment that facilitates
wireless communication between user equipment (UE) and a network.
• It encodes, encrypts, modulates and feeds the RF signal to antenna.
• It produces time and frequency synchronization signals.
• It does power control and frequency hopping too.
BASE STATION CONTROLLER (BSC):
• Its main work is to control several transceivers.
• Switching between BTSs
• Managing of network resources
• Mapping of radio channels
8.2.2 NETWORK AND SWITCHING SUBSYSTEM:
This subsystem does mainly switching, mobility management, interconnection to
other networks, system control.
1. MOBILE SERVICES SWITCHING CENTRE (MSC):
It controls all connections via a separated network to/from a mobile terminal within
the domain of the MSC – several BSC can belong to a MSC.
Home Location Register (HLR):
Central master database containing user data, permanent and semi-permanent data of
all subscribers assigned to the HLR (one provider can have several HLRs).
Visitor Location Register (VLR):
Local database for a subset of user data, including data about all user currently in the
domain of the VLR.
8.2.3FUNCTION OF MAIN SWITCHING CENTER (MSC):
• Manages communication between GSM and other network (PSTN, Data
Network and GPRS).
• Call setup basic switching, call handling.
• Location register
• Billing for subscriber
8.3 FEATURES OF GSM:
• GSM is already used worldwide with over 450 million subscribers.
• International roaming permits subscribers to use one phone throughout Western
Europe. CDMA will work in Asia, but not France, Germany, the U.K. and other
popular European destinations.
• GSM is mature, having started in the mid-80s. This maturity means a more stable
network with robust features. CDMA is still building its network.
• The availability of Subscriber Identity Modules, which are smart cards that
provide secure data encryption give GSM m-commerce advantages.
CHAPTER – 9
GENERAL PACKET RADIO SERVICE (GPRS)
General packet radio service (GPRS) is a packet oriented mobile data service
available to users of the 2G cellular communication systems, global system for mobile
communications (GSM), as well as in the 3G systems. In 2G systems, GPRS provides
data rates of 56-114 kbps. It provides moderate speed data transfer, by using unused
time division multiple access (TDMA) channels.
Its supported protocols are Internet Protocol (IP), Point to Point Protocol (PPP) and
GPRS data transfer is typically charged per megabyte of traffic transferred, while data
communication via traditional circuit switching is billed per minute of connection
time, independent of whether the user actually is using the capacity or is in an idle
state. GPRS is a best effort packet switched service, as opposed to circuit switching,
where a certain Quality of service (QoS) is guaranteed during the connection for non-
GPRS extends the GSM circuit switched data capabilities and makes the following
• “ Always on” Internet access
• Multimedia messaging service (MMS)
• Push to talk over cellular (PoC/PTT)
• Instant messaging and presence – wireless village
• Internet applications for smart devices through wireless application protocol
• Point to Point (P2P) service: inter-networking with the internet (IP).
• Increase message sending speed 30 messages per minute approximately.
CODE DIVISION MULTIPLE ACCESS (CDMA)
Code Division Multiple Access (CDMA) consistently provides better capacity for
voice and data communications that other commercial mobile technologies, allowing
more subscribers to connect at any given time, and it is the common platform on
which 3G technologies are built.
CDMA is a spread spectrum technology, allowing many users to occupy the same
time and frequency allocations in a given band/space. As it name implies, CDMA
assigns unique codes to each communication to differentiate it from others in the
same spectrum resources, CDMA enables many more people to share the airwaves at
the same time than do alternative technologies.
10.1 ADVANTAGES OF CDMA:
• Increased cellular communications security.
• Simultaneous conversations
• Increased efficiency, meaning that the carrier can serve more subscribers.
• Smaller phones
• Low power requirements and little cell-to-cell coordination needed by
• Extended reach-beneficial to rural users situated far from cells.
10.2 DISADVANTAGES OF CDMA:
• Due to its proprietary nature, all of CDMA’s flaws are not known to the
• CDMA is relatively new, and the network is not as mature as GSM.
• CDMA cannot offer international roaming, a large GSM advantage.
10.3 DIFFERENCE BETWEEN CDMA AND GSM:
• The GSM stands for global system for mobile communication and CDMA for
code division multiple accesses.
• GSM is a form of multiplexing, which divides the available bandwidth among
the different channels. Most of the times the multiplexing used are either TDM
(Time Division Multiplexing) or FDM (Frequency Division Multiplexing). On
the other hand CDMA is a type of multiple access scheme (which means
allotting the given bandwidth to multiple users) and makes use of spread
spectrum technique which is essentially increasing the size of spectrum.
• In CDMA each user is provided a unique code and all the conversations
between 2 users are coded. This provides a greater level of security to CDMA
users than the GSM ones.
FIBER OPTIC TRANSMISSION SYSTEM
Optical Fiber is new medium, in which information (voice, Data or Video) is
transmitted through a glass or plastic fiber, 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 Fiber.
(4) A Detector Changes the Light Signals into Electrical Signals.
(5) Electrical Signals are decoded into Information.
FIG 11.1 OPTICAL FIBER TRANSMISSION (REF- 1)
11.2 ARCHITECTURE OF FIBER:
The optical fiber has two concentric layers called the core and the cladding. The inner
core is the light carrying part. The surrounding cladding provides the difference
refractive index that allows total internal reflection of light through the core. The
index of the cladding is less than 1%, lower than that of the core. Most fibers have an
additional coating around the cladding. This buffer coating is a shock absorber and
has no optical properties affecting the propagation of light within the fiber.
Light at less than
critical angle is
absorbed in jacket
Light is propagated by
total internal reflection
Fig. Total Internal Reflection in an optical Fibre
FIG 11.2 PROPAGATION OF LIGHT THROUGH FIBRE (REF- 1)
There are three types of fibers:
(I) Multimode Step Index fiber (Step Index fiber)
(II) Multimode graded Index fiber (Graded Index fiber)
(III) Single- Mode Step Index fiber (Single Mode fiber)
(I) STEP-INDEX MULTIMODE FIBER: It has a large core, up to 100 microns in
diameter. As a result, some of the light rays that make up the digital pulse may travel
a direct route, whereas others zigzag as they bounce off the cladding. This type of
fiber is best suited for transmission over short distances, in an endoscope, for instance.
(II) GRADED-INDEX MULTIMODE FIBER: It contains a core in which the
refractive index diminishes gradually from the center axis out toward the cladding.
The higher refractive index at the center makes the light rays moving down the axis
advance more slowly than those near the cladding. A digital pulse suffers less
(III) SINGLE-MODE FIBER: It has a narrow core (eight microns or less), and the
index of refraction between the core and the cladding changes less than it does for
multimode fibers. Light thus travels parallel to the axis, creating little pulse
dispersion. Telephone and cable television networks install millions of kilometers of
this fiber every year.
11.4 ADVANTAGES OF FIBRE OPTICS:
• SPEED: Fiber optic networks operate at high speeds - up into the gigabits.
• BANDWIDTH: large carrying capacity.
• DISTANCE: Signals can be transmitted further without needing to be refreshed or
• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or
other nearby cables.
• MAINTENANCE: Fiber optic cables costs much less to maintain.
Advanced Optical Networks: DWDM
(DENSE WAVELENGTH DIVISION MULTIPLEXING)
The revolution in high bandwidth applications and the explosive growth of the Internet,
however, have created capacity demands that exceed traditional TDM limits. To meet
growing demands for bandwidth, a technology called Dense Wavelength Division
Multiplexing (DWDM) has been developed that multiplies the capacity of a single fiber.
DWDM systems being deployed today can increase a single fiber’s capacity sixteen fold,
to a throughput of 40 Gb/s. The emergence of DWDM is one of the most recent and
important phenomena in the development of fiber optic transmission technology. Dense
wavelength-division multiplexing (DWDM) revolutionized transmission technology by
increasing the capacity signal of embedded fiber.
One of the major issues in the networking industry today is tremendous
demand for more and more bandwidth. Before the introduction of optical networks, the
reduced availability of fibers became a big problem for the network providers. However,
with the development of optical networks and the use of Dense Wavelength Division
Multiplexing (DWDM) technology, a new and probably, a very crucial milestone is being
reached in network evolution. The existing SONET/SDH network architecture is best
suited for voice traffic rather than today’s high-speed data traffic. To upgrade the system
to handle this kind of traffic is very expensive and hence the need for the development of
an intelligent all-optical network. Such a network will bring intelligence and scalability to
the optical domain by combining the intelligence and functional capability of
SONET/SDH, the tremendous bandwidth of DWDM and innovative networking software
to spawn a variety of optical transport, switching and management related products.In
traditional optical fiber networks, information is transmitted through optical fiber by a
single light beam. In a wavelength division multiplexing (WDM) network, the vast
optical bandwidth of a fiber (approximately 30 THz corresponding to the low-loss region
in a single mode optical fiber) is carved up into wavelength channels, each of which
carries a data stream individually.
The multiple channels of information (each having a different carrier
wavelength) are transmitted simultaneously over a single fiber. The reason why this can
be done is that optical beams with different wavelengths propagate without interfering
with one another. When the number of wavelength channels is above 20 in a WDM
system, it is generally referred to as Dense WDM or DWDM.
DWDM technology can be applied to different areas in the
telecommunication networks, which includes the backbone networks, the residential
access networks, and also the Local Area Networks (LANs). Among these three areas,
developments in the DWDM-based backbone network are leading the way, followed by
the DWDM-based LANs.
DEVELOPMENT OF DWDM TECHNOLOGY
Early WDM began in the late 1980s using the two widely spaced wavelengths in
the 1310 nm and 1550 nm (or 850 nm and 1310 nm) regions, sometimes called wideband
WDM. The early 1990s saw a second generation of WDM, sometimes called narrowband
WDM, in which two to eight channels were used. These channels interval of about 400
GHz in the 1550-nm window. By the mid-1990s, dense WDM (DWDM) systems were
emerging with 16 to 40 channels and spacing from 100 to 200 GHz. By the late 1990s
systems had evolved to the point where they were capable of 64 to 160 parallel channels,
densely packed at 50 or even 25 GHz intervals. As fig. 1 shows, the progression of the
technology can be seen as an increase in the number of wavelengths accompanied by a
decrease in the spacing of the wavelengths. Along with increased density of wavelengths,
systems also advanced in their flexibility of
configuration, through add-drop functions, and management capabilities.
Engineering student will have to serve in the public and private sector industries and
workshop based training and teaching in classroom has its own limitation. The lack of
expo sure to real life, material express and functioning of industrial organization is the
measure hindrance in the student employment.
In the open economy era of fast modernization and tough competition, technical
industries should procedure pass out as near to job function as possible.
Practical training is one of the major steps in this direction. I did my training from
BSNL, Bharatpur which is one of the best known communication service provider
companies of India. The training helps me in gaining in depth knowledge of the
working of telephone exchange, various technologies of BSNL –GSM, GPRS,
WIMAX, Wi-Fi, MLLN and optical fiber transmission.
In the end, I hereby conclude that I have successfully completed my industrial training
on the above topics.
BIBLIOGRAPHY AND REFERENCES
1. Data Communication And Networking- Behrouz A. Foruzan
2. Wireless Communication and Networks-William Stallings
3. Computer Networking – Kurose & Ross