Bsnl Report

UNIVERSITY INSTITUTE OF ENGINEERING AND TECHNOLOGY

HIET (GHAZIABAD)2010

Report on

TELECOMMUNICATION NETWORKSIn partial fulfillment for the degree of bachelor of technology in electronics and communication

engineering

SUBMITTED TO-

SARSIJ SAURABH D.E.(TAX)

BSNL, MALL ROAD, KANPUR.

TRAINING INSTRUCTOR TRAINING INSTRUCTOR

Er.SUDHEER K. SINGH Er. SUSHIL K. SINGHINSTRUCTOR INSTRUCTOR O/oDE, TAX O/oDE, TAXBSNL, THE MALL, KANPUR BSNL, THE MALL, KANPUR

Submitted by:

DURVESH HARI NARAYAN SINGHB.TECH (IT)

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2010

Acknowledgement

I did my summer training from BHARAT SANCHAR NIGAM LIMITED, The Mall, Kanpur.My vocational training of four weeks completed successfully. During my training period, I got full support of the corporation employees.

I would like to express my sincere thanks to SARSIJ SAURABH ,ITS the honourable, divisional engineer of BSNL, The Mall, Kanpur who gave me the opportunity and his very much needed consent to undergo vocational training under his supervision.

Special thanks to Er.RAVINDRA PRATAP SDE(TAX), for his time to time, very much needed and valuable guidance. Without his full cooperation and guidance, my vocational training would not have been successful in due coarse of time. I express my gratitude towards Er.SUSHIL KUMAR SINGH, training instructor, who gave me the proper insight view of the TAX division without which it would have not been possible for me to understand the working of the TAX division.

I am also grateful to my friends for constantly supporting me, encouraging and helping me out during the period of my training.

Lastly, I would like to thanks my parents for giving me the moral support which I required during the course of completion of the vocational training.

DURVESH HARI NARAYAN SINGH B.TECH (IT)final year

2010

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Contents

1. Introduction 1

1.1. About BSNL 1

2. Introduction to telecommunication networks 2

3. Telecommunication network and the layered model 3

4. Network architecture 8

5. Structure of the access network 8

5.1 Main network involve in communication 8

5.1.1 Outdoor network 8

5.1.1.1. A) Distribution point

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5.1.1. B) Pillar 11

5.1.1. C) Main distribution Frame 11

5.2 Indoor network 12

5.2.1Types of exchanges 12

5.3 Transmission network 12

6 Siemens Digital Switching System 13

6.1EWSD for all network level 14

6.1.1Local network nodes and access network 14

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6.1.2Transit network nodes 14

6.1.3International network nodes 14

6.1.4Combined network nodes 14

6.2EWSD Power nodes 15

6.3About EWSD 16

6.4EWSD Periphery Components 17

6.4.1CP (Central Processor) 17

6.4.2Signaling System Network Control (SSNC) 17

6.4.3MB (Message Buffer) 17

6.4.4CCNC (Common Channel Network Control) 18

6.4.5Remote Switching Unit (RSU) 18

6.4.6DLU (Digital Line Unit) 18

6.4.7SN (Switching Network) 19

6.5Software 19

6.6Technical data 19

7 Important features of EWSD 20

8 References 21

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INTRODUCTION

1.1 About BSNL

BSNL or Bharat Sanchar Nigam Limited is India’s largest Communication Service

provider (CSP) and seventh largest in the world. Previously known as DoT (Department

of Telecommunications) when it was under federal government control, it became a

corporation in 2000.

BSNL operates across the length and breadth of country (except the metropolitan cities of

Mumbai and New Delhi which is managed by MTNL) and commands over 40 million

landlines and 18 million subscribers. Since its corporisation in October 2000, BSNL has

been actively providing connections in both Urban and Rural areas and the efficiency of

the company has drastically improved from the days when one had to wait for years to

get a phone connection to know when one can get a connection in even hours.Pre-

activated Mobile connections are available at many places across India.

BSNL has also unveiled very cost-effective Broadband Internet access plans targeted at

homes and small businesses.BSNL plans to add 20 million subscriber annually for the

next three years and the long term target of 120 million lines by 2010.with the frantic

activity in the communication sector in India, the number will be easily achievable.

Today,BSNL is the No.1 communication Company and the largest Public Sector

Undertaking of India with authorized share capital of $3977 million and net worth of

$1432billion.

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With latest digital switching technology like OCB,EWSD,AXE-10,NEC etc. and

widespread transmission network including SDH system up to 2.5 Gbit/s,DWDM system

up to 80 Gbit/s,Web telephony,DIAS,VPN,Broadband and more than 400,500 data

customers.

2. Introduction to telecommunication networks

Telecommunications today is perhaps the fastest evolving field of study. It is continuously offering new challenges and opportunities to telecommunications network planners. The subscriber part of the telecommunications network or the network connecting the subscribers to the central office or the access network that has been traditionally simple twisted copper pair based, point to point, passive network is now becoming increasingly complex. In the present scenario it becomes imperative for the access network planner to be familiar with both traditional and new technologies, structures and methods as their plans would have a profound long term impact on how the network shapes up and meets the desired objectives.

The basic idea of telecommunication is the exchange of information.

The information may include voice, text, data, image and video. A telecommunications network is therefore a system which can provide these services to a number of end users. From the end users' perspective, the network has some main tasks:

Make interconnection of end users possible

Facilitate exchange of information in a form desired and suitable for their

terminals

Send and receive signals to/from the end users to facilitate the establishment,

maintenance and dismantling of connections

Provide additional services such as wake-up calls, billing information etc.

It is very important for network planners to pay attention to the technical evolution of telecommunication systems. This would to enable proven new technologies to provide high quality telephone service and meet demands of new telecommunication services. Owing to prospective development of these technologies and increasing demand for new services other than telephony, telecommunication networks are changing from partly analog to fully digital.

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Demand and traffic patterns will change faster in the future than they do today. To cope with this, one important property a network should have is flexibility. Flexibility in simple term implies being able to provide bandwidth on demand. If bandwidth can be provided on demand then the network becomes capable of deploying and supporting a vide variety of services and with greater ease and speed.

3. Telecommunications network and layered model

Subscribers of a local area (municipal area or calls within which area charged at a

uniform rate) are connected to their respective telephone exchange called local-exchange

or local switch or terminal exchange.

The local area could be a single exchange local area in which case all the subscribers are

terminated on the same switch or a multi-exchange area when the number of subscribers

is large and one exchange cannot effectively and economically serve all the subscribers.

In the case of multi-exchange area each local exchange has its own area called exchange

area and the envelope of all exchange areas would be the local area.

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Calls among subscriber of the same exchange can be switched through without the need

of any other kind of links except the pairs linking subscribers to this exchange.

In a multi-exchange area, however, the subscribers connected to different local exchanges

can only communicate if the exchanges themselves are linked. These links between the

local exchanges are called junctions.

 Whereas each subscriber normally has one dedicated pair up to the exchange, the

junctions are dimensioned based on the traffic between exchanges and the grade-of-

service required.

A multi-exchange local area may have another type of exchange called transit or local

transit. A transit, unlike a local exchange, does not has subscribers connected to it and

therefore does not act as a source or sink for traffic in the network. It only collects and

redirects the traffic among the local exchanges in the local area. An example of such a

network is shown below.

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Here the diagram depicting the junction network also shows a new element viz. a local

transit exchange (TR). A transit would normally be used in bigger sized network to ease

traffic routing and cost-optimizing the junction network. In this example the local area of

the city is geographically divided into two by a physical obstruction i.e. the river and the

transit would make it easier and less expensive to interconnect the local exchanges on

both the sides to each other as also the local exchanges on the other side to the national

switch.

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The term local network is used denote the network in a local area: This would therefore

refer to the access network, the junction network, the local switches and local transits

(tandems), if installed.

It may be noted in the diagram that all the interexchange circuits are junctions. The term trunk-junction has been used just to differentiate between the two types of circuits shown. The national switch may be located in the same building as one or more local exchanges but is still not a part of the local network

The links that would be required if the subscribers of two different local areas need to communicate are discussed below.

As we linked all the local exchanges of one local area to each other, we could also directly link all the local exchanges of one local area to all the exchanges of other local areas in the country. This, though technically feasible, would be economically a disaster. Telecommunications network therefore have another type of exchange called national switch or trunk automatic exchange. All the local exchanges of one local area are connected to at least one such switch. All the national switches of a country are then

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connected to each other based on the switching plan. A national switch is also a type of transit exchange as it collects and redistributes traffic.

All the international calls are routed through international gateways to which the national exchanges would be connected. International gateways of different countries would be linked through terrestrial, submarine or satellite links.

The links among national switches, among international switches and between national and international switches are called trunks.

The telecommunications network can be described by a layered model consisting of the following layers:

1. The Switching and Services layer consists of all the switching nodes, local as well as transit. It also consists of any other equipment and like computers and software used to provide services to the customers.

2. The Transport Layer represents the links among the nodes and provides the medium and systems to carry the information from one node to the other. These are junctions and trunks. Junctions are links between the local switches and local and national switches. Trunks are the links between the national switches, the national and international switches and between the international switches i.e. the long distance network. The long distance or trunk network is composed of multiplexed channels of varying capacity connecting the National Switches and the International Switches. The trend has been to move from point-to-point links using Plesiochronous Digital Hierarchy (PDH) towards advanced networks with built in controllability based on Synchronous Digital Hierarchy (SDH) technique. The two most important trends in the long distance networks are digitization and introduction of fiber-optic technologies. These developments have reduced the transmission cost per channel-kilometer and improved the quality.

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3. The Access Layer represents the access network that links the customers to the local switch.

4. Network Architectures

Three basic patterns of interconnecting switching centers are mesh, star and ring formations. Actual networks are a result of combination of these basic types.

A full mesh is one in which each node is connected to all other nodes. How many one way circuits would be required to achieve this? Well, for an n-node network n*(n-1) one way circuit groups are required or half of that if both way circuits are used.

In star configuration all calls between any two switching centers of the same level are routed through a transit exchange at a higher level.

Rings connect switches in a closed path. Traffic can be carried both in the clockwise and anti-clockwise directions. Rings offer more reliability as they offer survivability in case of single link failures

5. Structure of the Access Network

5.1 Main network involves in communication

There are mainly three network involve in communication

1. Outdoor-Network2. Indoor-network3. Transmission network

5.1.1. Outdoor Network

Outdoor network is a network that connects to the exchange. In the network we use cable (like copper cables) for connecting the subscriber. There are many parts of the network which are described below:1) Distribution points2) Pillars3) Main Distribution Frame (MDF)

The minimum requirement between the user equipment and your switch is a pair of copper conductors.

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Fig 1. Simple interconnection of subscribers to exchange

The planner of such a network does not have much choice. In fact he does not have much of role in such a network. Since each pair is laid on demand he does not provide for future. There is no flexibility in the network. If another customer next door to the existing customer asks for a connection then another pair has to be laid right from the exchange to the customer. All this leads to repeated in fructuous work and increases material and labour cost.

5.1.1 A) Distribution points

If we lay slightly bigger cables, say 10 or 20 pair cables up to the vicinity of a a group of tenancies, then any nearby subscriber can be given service much faster by allocating one of the spare pairs. The multi-pair cable is terminated in a box which is called a distribution point (DP) as the pairs are distributed to subscribers from here.

This makes life easier but only a little bit. Any of the 20 pairs going to DP1 or 10 pairs going to DP2 can be given to any of the customers the designated areas of these DP’s. Laying and managing one 20 or 10 pair cable from the exchange to the DP may be a bit easier than dealing with individual pairs in these sections. This is definitely an improvement over the situation that we had before. However, consider a case where if all the 10 pairs of the cable going to DP2 get exhausted and there are more subscriber in this area while on the other hand the 20 pair cable going to DP1 still has half the pairs unused! This situation is not uncommon where pairs are available but not at the places where they are required. How can we make use of the extra pairs of DP2 area for customers in DP1 area?

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Fig 2. Introducing distribution points several subscribers into DPs we could group a number of DPs and serve them with a common cable. We need to set up another point, a cross connection point, up to which we would bring a still larger cable than we brought to the DP and serve a number of DPs from that point. Let's see how it will look.

Now there is one larger cable going to the cross connection point (CCP). This CCP provides the capability of connecting any of the pairs of this cable to any of the DPs, in its area, thus offering great flexibility in pair management for this reason a CCP is also called a flexibility point. Introduction of a CCPcould be called a revolutionary change in the access network. A common name for this cross connection point is cabinet. An urban network would have a number of cabinets each serving a number of DPs. The cabinet area may have hundreds of customers while the DP areas would have tens of customers.

On a pessimistic note one could argue that now we have big cables going from the exchange up to the cabinets. We could for example have a 1200 pair cable going to one cabinet and say a 800 pair going to the other. Now if we have exhausted all the pairs of one of them then would it be possible to use pairs from the other for the customers in the exhausted area? Again a case of pairs being available in the network but not at the right place!

To make a larger part of the cable common to many more subscribers we could add one more cross connection point. Isn’t this going too far? How many cross connection points can we possibly have between the exchange and the DP? Theoretically as many as the designer wants but going by the international norms up to two such cross-connection points are used. If we did this the network would look like this:

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5.1.1 B) Pillars

The above structure has all the rudiments of the real-life access network. The first CCP from the exchange is called the Primary Cross-connection Point (PCP) or the cabinet and the cable linking the PCP to the Exchange is known as the Primary cable. The network of all the cabinets and the primary cables is referred to as primary network. The second CCP is known as the Secondary Cross-connection Point (SCP) or the pillar and the cables linking pillars to the cabinet are known as secondary cable. The cables linking DPs to the SCP are known as Distribution cables and together the distribution cables, DPs and other related infrastructure form the distribution network.

So what are the advantages of having cabinets (and possibly pillars) in the network instead of having direct pairs from the exchange to the customers? We surely have not incurred the extra cost of installing cabinets and pillars for fun! Let's enumerate some of these..

1. These flexibility points divide the network between the exchange and the DPs into sections as seen above. This gives the flexibility of planning and constructing different parts of the access network at different times and by different planners.

2. Any pair of the primary cable can be "jumpered" to any pair of any of the distribution cables in the same cabinet thus making a large part of the cable common to a larger number of subscribers. In two CCP networks the same flexibility is available on both the flexibility points

3. Planning of the network now involves providing pairs flexibly for a number of years. Larger cables ensure availability of enough spare pairs during the planning period to provide service on demand.

4. Construction of the plant is eased because we are laying large cables in place of laying one pair at a time. This saves on construction labour cost and time.

5. Maintenance becomes easier as cabinets and pillars provide good test points for testing different parts of the plant. Once the fault has been localized, only the affected part (Primary, secondary or distribution) cable pair can be replaced.

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6. Cost of the network is optimized as the pairs are more efficiently utilized. Effort and labour cost for construction and maintenance are reduced. Cable cost comes down as per pair cost in the larger cable is less than cost of single pair cables or cost per pair in small sized cables.

7. Time taken to construct and maintain the flexible network is much less than rigid networks with no flexibility points.

5.1.1 B) Main Distribution Frame (MDF)Main distribution frame is a wiring arrangement which connect the telephone lines coming from outside on one side and internal line on the other. This panel might also carry protective devices as well as function as testing point. it is the main frame of the distribution of cables. The cables from the exchange first terminate at MDF and then from MDF to pillar.MDF has two sides .First is exchange side and second is line side. At line side cables coming from pillars are terminated and at exchange side MDF is connected to the exchange.

5.1.2. Indoor Network

Network inside in exchange is known as indoor network. It is also called switched room because it is use to switch (connect) one subscriber to other. When a person dials a number then whole process is inside the exchange.

The Indian telecom department promotes some new technologies to set up in India.These technologies are very much stable and flexible and by using these technologies working speed drastically increases.

Some of these new technologies are-1. EWSD by Siemens (Germany)2. AXE-10 by Ericsson (Sweden)3. FETEX-150 by Fujitsu (Japan)4. OCB-28 by Alcatel (France).

The technology used in BSNL (The Mall, Kanpur) is EWSD.

5.1.2. A) Types of Exchange

EWSD (Electronische Whealer System Digitalate) Exchange 1. E-10B (Electronic – 10 Binary ) Exchange 2. WLL ( Wireless in local loop ) Exchange 3. OCB Exchange 4. C-DOT ( Center of Development of telementry ) Exchange

5.1.3. Transmission Network:-

The EWSD Data Tandem switch enables network operators to route calls directed to local ISPs on to dedicated SS7 trunks connected to a centrally located EWSD system.

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The EWSD system then grooms this traffic onto dedicated PRI trunks connected to the indiv dual ISPs. The Internet has spurred a communication revolution. Irving an increase in data traffic that is congesting today’s public switched telephone network (PSTN). With the average call holding time for Internet calls lasting 22 minutes. Versus the average three minute length of a voice call, the internet is choking the telecommunications network, raising operational cost and affecting the quality of service expectations. Plus network operators are faced with having to make a significant number of switch upgrades just to address the demand for internet services.Since data traffic is growing faster than voice traffic on PSTN, network operators are faced with the challenge of managing the dramatically increased level of network traffic.It’s a welcome challenge since it represents a new arena of opportunity for service

providers. Siemens information and communications network offers EWSD internet

solutions, a phased migration strategy to help optimize network resources. The EWSD

Internet solutions are a key part of Siemens powerful network vision.

6. Siemens Digital Switching Systems

Siemens of Germany is a well-known manufacturer of telephone equipment. Their main switch for

the public switched telephone network is the EWSD for both the North American and world

markets. Siemens started the manufacture of the EWSD in 1976.

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Siemens EWSD switch

6.1 EWSD for all Networks Levels

It is the solution for the local networks, transit networks, international gateway networks and a combination of all of the above. What’s more, wherever your EWSD node is used in the network, it can also serve as a Service Switching Point (SSP) in the Intelligent Network (IN) EWSD incorporates all these functions within a single platform.

6.1.1. Local Network nodes and access networks

Local network nodes are used for switching incoming and outgoing subscriber traffic up to 600000 subscribers can connect to a EWSD local network node via a complete range at subscriber interfaces, including:

Analog linesISDN Basic Access (ISDN-BA)ISDN Primary rate Accesses (ISDN-PA0V5.1 and V5.2 interfaces

Depending on your needs, subscriber interfaces are aggregated directly in the EWSD host exchange, or in Remote Switching Units (RSU).The Remote Switching Unit offers a capacity of up to 50000 subscriber with RSU internal traffic switched locally to avoid traffic load on the transport links to the host EWSD.Small, remote DLU can be attached as indoor or outdoor installations at both the EWD host exchange and the relatively larger RSU, so as to shorten the distance to the subscriber premises.

6.1.2 Transit Network Nodes

In transit or long distance network nodes, interrogational and mobile traffic is switched to and from other network nodes. Up to 240000 trunks may be connected to a EWSD transit network node.

6.1.3 International Network Nodes

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The primary task of the international network node is the switching of international and intercontinental traffic. All functions required for international nodes are in EWSD, such as:

a. International signalingb. Echo compensation for intercontinental and satellite connectionsc. Inter-administrative charging

6.1.4 Combined Network nodes

The function of local network nodes, transit network nodes and international network nodes can be combined in a single EWSD network node.

6.2 EWSD POWER NODE

It provides your universal high performance switching platform for rising subscriber

traffic growing bandwidth converging voice and data. It allows easy and cost – effective

consolidation of your network.

THE EWSD POWER NODE is characterized by ………..

A single architecture for the global market.

A generic platform for all network applications

An evolution path from narrowband to broadband

Evolution from voice to a mixed voice and data networks

Exploiting, enhancing and consolidating existing networks

Easy operation and low maintenance cost

The all in one solution EWSD Power node covers all network applications such as

Local exchanges

Tandem exchange

Transit/toll exchanges

National and international gateway exchange

Service Switching Point (SSP) to Intelligent Network (IN)

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Stand alone signaling transfer point (STP)

6.3 About Electronic Worldwide Switch Digital (EWSD)

The full name of EWSD in German is”Electronische Whealer System Digitalate” which means in English is ‘Electronic Digital Switching System’-Unmatched Switching.

EWSD End Office Switch

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EWSD is one of the most widely installed telephone exchange systems in the world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or mobile phones. It is manufactured by Siemens AG, who claims that EWSD switches perform switching for over 160 million subscriber lines in more than 100 countries.

DeTeWe bought its first EWSD under license in 1985 for remote switching. Bosch built its first EWSD as a local exchange in 1986. Deutsche Telecom, formerly Deutsche Budapest, the largest German telephone company, uses EWSD and System 12 (Alcatel), the former more than the latter.

In 2007, Nokia Corporation and Siemens AG formed the new company Nokia Siemens Networks, and responsibility of further development and shipments of the EWSD system is dependent on this new company.

6.4 EWSD Periphery Components

The following are the components of the EWSD- CP (Central Processor) Signaling System Network Control(SSNC) MB (Message Buffer) CCNC (Common Channel Network Control) Remote Switching Unit(RSU) DLU (Digital Line Unit) SN (Switching Network)

All system units are redundant so the inactive side can take over immediately in case of an error.

6.4.1. Signaling System Network Control (SSNC)

The Signaling System Network Control (SSNC) is the high performance EWSD component for SS7 signaling, supporting& over TDM, SS& over ATM and also SS& over IP.

6.4.2. Message Buffer

The message buffer is the part of coordination processor of EWSD and switches the signaling between the different control units involved in call setup and clear down.

6.4.3. Digital Line UnitIt is the functional unit on which subscriber lines are terminated. it offers top performance and significant cost saving for the network operator.DLU is able to handle rising subscriber traffic (e.g. more subscribers per line card, Internet dial up).

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Analog or digital subscribers or PBX lines are terminated on DLU.DLU can be used locally within the exchange or remotely as remote switch unit in the vicinity of the group of subscribersDLU are connected to EWSD subsystem via primary digital carrier (PDC) to facilitate to local or remote installation.One DLU is connected to two different LTG’s for the reason of security. A local DLU is connected to two LTG’s via 4Mbps links each towards a different LTG.In case of remote DLUs maximum 4PDCs of 2Mbps are used per DLU towards each LTG. Hence 124 channels are available between a DLU and two LTG’s out of which 120 channels are used for information (speech or data) and signaling information is carried in TS 16 of PDC 0 and PDC 2.

The main benefits are:a) Future proof: able to handle increasing Internet trafficb) 50% less space per subscriber linec) 30% less power consumptiond) Part of next generation network migration path

6.4.4. LINE TRUNK GROUP

The line trunk group forms the interface to the switching network for the subscriber and trunk connections. In addition, it performs such functions as receiving dialing information, producing call charges records, line supervision and echo cancellation.

The latest type of LTG offers the following advantages:a) 50% less power consumptionb) 1.5 times higher performance.c) Optical or electrical interface to the switching network

The main functions of LTG are a) CALL PERFORMANCE FUNCTION- this means receiving and analyzing

such that line and register signals, injecting audible tones switching channels, from and to the switching network etc

b) GUARDING FUNCTIONS SAFELY- this detects errors in LTG and in transmission path with the LTG analyzing the extent of errors and initiating counter measures such as disabling channels or lines.

c) OPERATION AND MAINTAINENCE FUNCTIONS-It carries out quality of service management and accrues traffic data.

6.4.5. Remote Switching Unit

When streamlining your existing network or designing new network, RSU can function as small network nodes providing the network operator with a varied, flexible and economical solution. The RSU can be located at any distance from the host exchange.Up to 50000 subscribers or 8500 trunks or combination if these can be connected to one RSU.

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Benefits:1. Reduces number of switches and reduced cost2. possibility of cascading additional remote DLUs3. stand alone operation including charging4. traffic offload due to internal switching5. internet offload6. part of next generation migration path

6.4.6. Coordination Processor

It is responsible for all call processing and routing tasks. It additionally performs common functions such as the coordination of data transfer between the distributed peripheral microprocessors. When operating at maximum capacity, the CP113 can handle up to 16 million Busy Hour Call Attempts (BHCA).CP handles the common functions in the exchange such as coordination of distributed microprocessor controls and data transfer between them

There are the following kinds of Co-ordination Processors:

CP103 with max 22,000 call attempts in the busy hour CP112 with max 60,000 call attempts in the busy hour CP113D with max one million call attempts in the busy hour CP113C with max six million call attempts in the busy hour CP113E with max ten million call attempts in the busy hour

6.4.7. The Switching Network

The Switching Network consists of 4 space division stages of 16x16 switches, and a time division section with 16 stages of 4x4 switches

6.5 Software

The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly written in the CHILL language. Application software is switch specific and serves among other things traffic management, path search, and call charging. Support software serves translating programs, binding modules as well as administration of libraries for generating data. Operating and data communication software serve for co-operation of maintenance centers and switching centers.

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6.7 Technical data Number of access lines: to 250,000 Number of feeder lines: 240,000 Traffic connection: 25,200 Call attempts in busy hour: 10 million Operating voltages: -48V -60V -90V Rate zones: 127, for each zone of 6 tariffs Tariff change-over at 15 minute intervals Space requirement with 10,000 access lines: 35 square meters

7. IMPORTANT FEATURES OF EWSD

1. Advancement Intelligent Network0.1 and 0.2 capabilities allow switching services

to be added at Service Control Points, meaning that new services can be added

and performed by the switching system without the customer having to buy new

equipment.

2. EWSD provides Integrated Services Digital Network.

3. Digital and analog lines can be combined in the same line group allowing full

interoperability between digital and analog terminals.

4. Carriers using EWSD can provide Automatic Call Distributors services for

customers with call center.

EWSD provides both Bell Communications Research AIN0.2 and Global System for

Mobile Communications for personal communication services.

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8. References

1. www.bsnl.co.in

2. http://en.wikipedia.org/wiki/Telephone_exchange

3. www.google.com

4. www.wikipedia.com

5. Notes given by Training Instructor.

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