1. Bharat Sanchar Nigam Limited (BSNL) is an Indian state-owned telecommunications company that provides telecom services across India. 2. BSNL provides various telecom services including wireless, broadband, internet, and landline services using technologies like GSM, CDMA, MPLS, VSAT, and VOIP. 3. When a subscriber makes a call, the request first goes to the nearest telephone exchange. The exchange processes the numbers and sets up the call either within its switching network or by transferring the call to other exchanges as needed.

1. AKGEC
Connecting India
BSNL
Arun Rajput
(1402731036)

2. Introduction to EWSD
Digital Line Unit (DLU)
Line/Trunk Group (LTG)
Switching Network
Signaling System Network Control (SSNC)
Coordination Processor (CP)
Message Buffer (MB)
Central Clock Generator Type E
Subscriber facilities
Integrated Service Digital Network (ISDN)
Signaling System No. 7
About BSNL
Call Setup
About the EXCHANGE
Talk Flow

3. About BSNL
Bharat Sanchar Nigam Limited (abbreviated BSNL) is an Indian Telecommunication
company of US$ 5.1 billion founded on 15 September 2000.
Its responsibilities includes improvement of the quality of already installed telecom
services, expansion of telecom services in rural areas and acquiring confidence among
its customers.
It provides a comprehensive range of services in India, which include wireless
connections, CDMA mobile, GSM lines, Internet, broadband, MPLS-VPN (multi
protocol label switching-virtual private network), VSAT (very small aperture terminal)
WIMAX, FTTHand VOIP (voice over Internet protocol).
Within this short span of time, it has also become one of the largest public sector
companies in India.

4. CALL SETUP
Telephone
Subscriber
Distribution
Point
Pillar Cabinet
Main
Distribution
Frame
Telephone
Exchange
When a subscriber calls to another subscriber first its request goes to the nearest switching
center that is PSTN (Public Switching Telecommunication Network). Then it processes the
caller and subscriber’s number if it exists in the same BSC (Base Station Controller) then call
setup is completed.
If subscriber is not in the same BSC then call transfer to MSC (Mobile 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(Mobile Telephone
Switching Office)
now call transfer is done on BTS (Base Transceiver Station) and call setup is completed.
How line reaches from subscriber to Exchange

5. About EXCHANGE
All telephone subscribers are served by automatic exchanges.
Today’s automatic exchanges use a pair of computers .One running the program that
provides services.
Second, monitoring the operation of the first, ready to take over in a few seconds in the
event of equipment failure.
Various exchanges present in BSNL
C-DOT
OCB (ORGANE DE COMMANDE B2 VERSION)
EWSD

6. Digital Electronic Switching System is the telephone exchange system, developed
by Siemens AG, Germany.
EWSD Functional Components
Digital Line Unit (DLU)
Line/Trunk Group (LTG)
Switching Network (SN)
Switching System Network Control (SSNC)
Coordination Processor (CP)
Message Buffer (MB)
Central Clock Generator (CCG)
Introduction to EWSD

7. EWSD-Hardware Overview
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8. DLU- Digital Line Unit
It is a functional unit on which subscriber lines are terminated.
DLUs are connected to ESWD sub-systems via a uniform interface
standardized by CCITT i.e PDC.
One DLU is connected to two different LTGs for the reasons of security via
4 Mbps links.
Total 124 channels are available
between a DLU out of which the
two LTGs Signalling information
is carried in PDC0 PDC2 .
PDC With CCS
PDC Without CCS
Analog/Digital
Subscribers
Analog/Digital
Subscribers
Single DLU Is connected to LTG with 4 PDCs.
Single DLU has 2 DLUCs, each is responsible for 2 PDCs.
Connectivity between DLU & LTG

9. DLU- Digital Line Unit
Type of DLUs
DLU-B DLU-D DLU-V DLU-G
Subscriber line module, analog (SLMA)
Subscriber line module, digital (SLMD)
Subscriber line module, internet (SLMI)
SLM, packet Hub (SLMPH)
Metallic Test Access (MTA)
Stand Alone Service Control (SASC)
External Alarm Set (ALEX)
Ringing and Metering Voltage Generator
Structure of DLU-G

10. LTG- Line/Trunk Groups
The line/trunk group(LTG) forms the interface between the digital environment of an
ESWD exchange & the switching network (SN).
Primary Functions of LTG
Maximum traffic handling capacity per LTG is 100 Erlang.
Call processing function:- receiving analyzing line & register signal.
Safeguarding function:- detecting error in the LTG & on transmission path within LTG.
Operation & Maintenance function:- acquiring traffic data, carrying out quality-to-.
service measurement.

11. SN- Switching Network
Different peripheral unit of ESWD i.e LTG, CCNC, MB are connected to the
Switching Network (SN).
Through 8192 kbps highway called SDCs (Secondary Digital Carriers), which have
128 channels each.
It consists of several duplicated Time Stage Group (TSG) & Space Stages Groups
(SSG) housed in separated racks.
Connection paths through the TSGs & SSGs
are switched by the SGC.
Each TSG can accommodate 63 SDCs from
LTGs & one SDC to MB
SDC
SDC
SDC

12. SN. Switching Network Multiplexer (SNMUX)
Switching network multiplexer, type A
(SNMUX (A) :-The SNMUX (A) processes 8-Mbit/s
electrical signals from the LTGs (copper wire access).
Switching network multiplexer, type B
(SNMUX (B) :-The SNMUX (B) processes 184-Mbit/s
optical signals or 8-Mbit/s electrical signals (copper wire)
from the line/trunk groups P (LTGP) or RSU.
It comprises the following:
– Interface module for LTG, type D (LILD)
– Multiplexer controller module (MUXC)
– Transmit and receive module for optical
connections (OML920).
It comprises the following:
– Interface module for LTG, type E (LILE)
– Multiplexer controller module (MUXC)
– Transmit and receive module for optical connections
(OML920).

13. SSNC-Signaling System Network Control
The Signaling System Network Control (SSNC) is the innovative component for high-powered SS7 signaling in
EWSD. Due to its configuration flexibility it can be deployed as a signaling end point (SEP), integrated signaling
transfer point (STP), signaling gateway (SG), or a combination of these functionalities.
The SSNC allows the separation of signaling from bearer and SS7 transfer and the conversion to all kinds of
underlying packet technologies like Internet protocol (IP) and asynchronous transfer mode (ATM). Beside that, the
SSNC can also work as a powerful Signaling Relay Point (SRP) and as a Number Portability (NP) Server for all
kind of number portability scenarios.
This enables a carrier grade service package to be offered to
multimedia users connected to EWSD:
Multiple SS7 Networks
High-Speed Signaling Links (HSL)
MTP Loadsharing
Global Title Translation (GTT)
MTP Route Verification Test (MRVT)

14. SSNC- Structure
T The ATM bridge processor, type C
(AMPC) is the interface between the ATM equipment on the ASN and the coordination
processor (CP113). It converts packet-oriented data flows from the ATM area to the CP
communication mode and vice versa. For functional purposes the AMPC belongs to the
SSNC, but it is located in the module frame of the CP.
The MP is connected to the internal transport system
via a high-speed ATM interface and provides optional external IP interfaces.The MP
hardware platform is the foundation for different software applications.
The line interface card (LIC) connects the SSNC to
the SS7 networks via up to 8 E1/DS1 links. The LICs are operated in a one-to-one
redundancy mode. They are connected with the internal transport system via a highspeed
ATM interface.
The internal transport system is implemented
via an ATM switching fabric and thus overcomes the limitations of conventional bus
systems. With its bandwidth of up to 20 Gbit/s, it provides ample capacity for future growth
of the system.
The hardware part consists of the following major components:
Main processor (MP):-
Line interface card (LIC):-
ATM switching network (ASN):-
ATM bridge processor, type C (AMPC):-

15. CP- Coordination Processor
Storage & administration of all programs, exchange & subscriber data .
Processing of received information for routing, path selection, zoning, charges.
Communication with operation & maintenance centers.
Supervision of all subsystems, receipt of error messages, alarm treatment, error
messages,
Handling of the man-machine interface.

16. CP- Coordination Processor
Common memory (CMY) :- 64 to 1024 MB in 4 memory bank consisting of 4
DRAM chip
Input/Output Control (IOC) :- 2 to 4 IOCs coordinate & supervise accessing of CMY
ATM bridge processor (AMP) :- If a SSNC ( EWSD powermode) is connected, the AMP
is used. It represents the interface between the ATM
equipment in the SSNC & the CP .
Input/Output processor (AMP) :-Various type of IOPs are used to connect the CP113E
to the other subsystems & functional unit of the
exchange as well as to the external mass storage
device.
Structure of CP113E
Base processor (BAP):- for operation, maintenance & call processing.

17. MB- MESSAGE BUFFER
The message buffer is used to coordinate the exchange of messages in the EWSD between:
Easy expansion to a maximum of 2016 LTG connections
Maximum reliability due to redundancy
Compact design with reduced footprint
Improved performance for the message channels
LTG SSNC SN CP
The main features of MB-D are:
Ethernet interfaces (10/100BaseT) for connecting SURPASS products
ATM interface to the SSNC to reduce the CP load when distributing messages in
the network node

18. CCGE- Central Clock Generator Type E
The central clock generator, type E (CCGE) supplies the network node with a highly accurate,
stable clock.
Four reference inputs per redundant unit, capable of processing different signals.
Filters to remove jitter and wander on the transmission links.
Automatic active/standby switchover after signal failure in the redundant unit.
Structure
Flexible expansion options to up to 2 x136 T4 outputs.
Rapid recovery after a power failure.
It provides 32 extension outputs (T4 clock outputs)
Synchronization module (CCGES) It control and synchronization module of the CCGE.
Clock distribution module (CCGED) operating at 2.048 MHz in four groups of eight outputs
each for the external users.
Benefits

19. Subscriber facilities
Call waiting
Selective Call Waiting
Call Forwarding
Rejection of forwarded calls
Multiple Simultaneous
Call Forwarding
Parallel Ringing Definition
Do Not Disturb
Distinctive Ringing
Automatic Recall
Fixed Destination Call
Calling Line Identification
Presentation on Call Waiting
Calling Line Identification
Presentation
Three-Party Conference (TPC)
Call Hold (CH)
Facilities provided by BSNL to their users

20. ISDN-Integrated Service Digital Network
ISDN Access Types
The ISDN standards define various services (bearer and tele services) and additional supplementary
services, which can be controlled by the subscriber by means of the functional and/or keypad protocol.
Basic access (BA)
Primary rate access
(PA)
Basic and primary rate access can be provided on the copper wire pairs
of existing subscriber lines as well as on parts of optical fibers.
The ISDN primary rate access is used for connecting larger ISDN private
branch exchanges, and provides 30 communication channels (B-channels)
and one signaling channel (D-channel). It is commonly referred to as
“30B+D”. Operating speeds for the B-channel are the same as for BA. The
D-channel provides for 64 Bits/s and is only used for signaling.
In contrast to existing public switched telephone networks, ISDN provides the
opportunity to operate a variety of different services over the same access line
(basic access), e.g. interrogating the newest products on the market via
videotex and simultaneously discussing them on the other channel.

21. Signaling System No. 7
SS7 PROTOCOL STACK
The hardware and software functions of the SS7 protocol are divided into functional abstractions called "levels". These
levels map loosely to the Open Systems Interconnect (OSI) 7-layer model defined by the International Standards
Organization (ISO).
Telephone User Part (TUP)
Signaling Connection Control Part (SCCP)
Transaction Capabilities Applications Part (TCAP)
ISDN User Part (ISUP)

22. AKGEC
Connecting India
BSNL

23. AKGEC
Connecting India
BSNL