introduction telcomm sw 1

8/6/2019 Introduction Telcomm Sw 1

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Subject

Subject: Telecomm Switching Principles

Credits: 3 + 0

Syllabus:

Introduction

Telecommunication Transmission

Evaluation of Switching

Telecommunication Traffic

Time Division Switching

Signaling

Networks (Numbering, Routing & Charging)


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Books

Text/ Reference Books:

Telecommunications Switching, Trafficand Networks (JE Flood)

Telecommunications Switching andNetworks (viswanath)

Telecommunication Switching Principles (MT Hills)


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Grading

End Term: 50%

Mid Term/One Hourly: 30%

Quiz: 10%

Assignment: 5% Project/Presentation: 5%

----------------------

No cheating in Quiz/ Assignments/ Exam

No Talking in class

No mobile phones


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Chapter # 1


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Development of Telecomm

Telecomm (distance communication)

Evaluation

Telegraph Morse\Wheat stone 1837

P to P, Uni directional Telephone Graham Bell 1876

1st Exchange New Haven\USA 1878

I believe, in the future, wires will unite Head

offices of telephone companies in different cities.A man in part of country may communicate by

word of mouth with another in distant place

Today, telecomm NWs are being used to provide

different types of Services


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NW Structure

NW Configurations

MESH

All subscribers have dedicated link to othersubscribers

Total # of Links would be N = n(n-1)/2

If n >> 1 then it becomes N = n 2

Only practicable if # of users are less & distancebetween them is short

BUS/RING Single cable is used to connect all users

Drawback ?

Suitable for data networks


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NW Structure

NW Configurations

Star

All subscribers have dedicated link to central

controller

Problem ? / # of Links ?

Solution : Hot standby

Unsuitable if # of users and distance increases

Star configuration introduces concept of switching Star & Mesh are two extremes , finally solution would

be a compromise between them


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NW Structure

# of exchanges

Single exchange will work If # of users are large and are not dispersed over

larger area

Else entire area should be divided intosmaller exchanges Wire cost

Exchange cost

Connection between exchanges cost

Therefore decision to increase number ofexchanges or wires is primarily dictated bycost


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NW Structure

Practical Limit on distance of Local Loop

Telephone set is being powered from

exchange which sets a limit on length of line

Line resistance should be less then 2000ohms to allow sufficient current flows for the

off hook condition to be detected by

exchange

Distance limitation can be improved by

using Good quality wire (less resistance)


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NW Structure

Junction Circuit / Tandem Exchange

If an area is served by # of LOCAL exchanges then there is aneed to have connections (Mesh) between them called

Junction (UK)

Trunk (USA)

If cost of providing junction circuit increases then we canconnect (Star) all LOCAL exchanges with central exchangecalled

Tandem exchange

Toll Office

In practical direct junction circuits only provided if Distance is short

Heavy traffic is expected between local exchange

Otherwise mixture of both i.e. some of the local exchanges canhave MESH rest all connected to tandem exchange through star


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NW Structure

Trunk routes/ Trunk Exchanges

Subscribers will like to talk with people inother parts of country also

Same logic can be extended to telephone

network serving country We use central exchange for each region

called Trunk exchange and they areconnected using trunk routes

Further network optimization is possible byusing trunk tandem exchange

Alternate routing is considered betweenthese exchanges to take care of faults/trafficload


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PSTN HierarchyAlso connected to

submarine cables andsatellite links.

Local Exchanges, or

End /class 5 Office

Local Tandem Exchanges, or

Central Offices (C.O.s)

Regional Tandem Exchanges, or


Local

network

TrunkNetwork

International

Network


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Telecommunication NW

Terminals End users devices connected to NW e.g. telephone,

computer

Transmission System

Provide circuits that connects two location e.g. medium Switching System

Equipment that routes information between NW terminals

Signalling System Information exchanged between subscriber and exchange

for establishment and for tearing down of connection Basic goal of NW design is to provide at maximum

interconnection at minimum cost


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Network Architecture

Customerterminals 20%

Outside plant,cables 29%

Switchingequipment 25%

Multiplexing andTransmissionequipment 15%

Buildings, land,other 11%


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Terminology UK

Local Exchange

Tandem Exchange

Regional Tandem Exchange National Tandem Exchange

International Gateway

USA End Office / Class 5Office

Class 4 Office

Class 3 Office

Class 2 Office

Class 1 Office

Internationally Primary switching center

Secondary switching center

Tertiary switching center


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PSTN Hierarchy

Local Exchanges, or

End /Office

Primary Switching

Centres

Secondary Switching

Centres

Tertiary Switching

Centres

International Gateway Exchanges

Also connected to

submarine cables andsatellite links.

Local Exchanges, or

End /class 5 Office

Local Tandem Exchanges, or


Regional Tandem Exchanges, or


LOCAL

Trunk

INT

Junction\Trunks Trunk\Junctor


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Regulators Telecommunication is mostly owned and controlled byGovernments

Regulatory authorities are used to ensure fair treatment toevery one subscribers, operators etc tariffs, frequencyallotment, fair market share

Pakistan PTA (Pakistan Telecommunication Authority)

UK OFTEL (Office of Telecommunication)

USA FCC (Federal Communication Commission)

In some countries telecommunication companies are privatelyowned e.g.

USA(Local/International) (Bell/MCI/SPRINT/AT&T/VERIZON)

UK (Local/International) (BT/Mercury telecommunication)


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STANDARDS Standards are must for interoperability

ITU is UN agency for information and communicationtechnologies

ITU is based in Geneva, Switzerland,

Its membership includes 191 Member States and more than 700

Sector Members and Associates Two main bodies

ITU-R (Radio communication Sector)

Developing standards for radio communication systems

Managing the international radio-frequency spectrum andsatellite orbit resources (FAB)

ITU-T (Telecommunication Standardization Sector)

Standards development

Large # of studied groups e.g. Group 11 signaling requirements

Group 13 future networks

Group 17 security


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OSI Model Telecommunication is mostly owned and controlled byGovernments









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OSI Model


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Regulators Telecommunication is mostly owned and controlled byGovernments









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Future Trends

Expansion to under dev countries (3 billion havenever used telephone)

Machine to Machine communication Computer are out numbering humans (By 2010 95% traffic

will be m to m)

Pervasive computing

Convergence Telephone, TV , Internet (NGN)

Devices (computer, TV)

NGN

A Next Generation Network (NGN) is a packet-basednetwork able to provide services includingTelecommunication Services and able to make useof multiple broadband, QoS-enabled transporttechnologies and in which service-related functionsare independent from underlying transport-related

technologies.

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