CETTM MTNL

1Overview of PSTN

OVERVIEW OF PSTN

MODULE ID: SPSTOVE002

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2Overview of PSTN

Topics

Public Switched Network

Hierarchy of Switches

PSTN N/W and Components

Long Distance (Toll) Network

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3Overview of PSTN

Public Switched Telephone Network

PSTN - public network for Voice Telephony

Major Components - PSTN Switch (Exchange) - Transmission facilities - Local Loop - Customer Premise Equipment (CPE)

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4Overview of PSTN

Typical Network

PSTN switch

CPE CPE

Transmission Facilities

PSTN Switch

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5Overview of PSTN

Public Switched Network

Switched network - Series of inter-linked nodes (switches)

Switches - hardware and/or software devices - capable of creating temporary connections between two or more devices linked to the switch but not to each other

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6Overview of PSTN

Customer Premise Equipment (CPE)

Term used to identify any piece of equipment supplied by the customer to interface with the PSTN.

CPE devices - POTS/ Telephone Set - FAX/Modems or Data Sets - Private Branch Exchange (PBX) - ISDN Terminals (NT-TA)

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7Overview of PSTN

External Plant Distributed N/W

U

Analogue subscriber

Pillar

Local Exchange

Pillar

Pillar

DigitalSubscriber

DP

DP

DP

DP

DP DP

DP DP

DPDP

DP

DP

DP

Pillar

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8Overview of PSTN

External Plant Cable Network

Exchange

Main DistributionFrame

Cable Chamber

Primary Cable

PillarDistributionPoint Box

Secondary Cable

Subscriber's Telephone

Dropwire

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9Overview of PSTN

Access N/W

Main Distribution

Frame

Digital Room

Local Exchange

DLC (Digital Loop Carrier)

RSU (Remote Subscriber Unit)

Access N/W

Access N/W

Access

N/W

Access N/W

Connecting Cable

Pillar DP

External Plant with DLC and RSU

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10Overview of PSTN

External network

Exchange

LE

TX system

TX system

TX system

Remote Unit

RU

RU

Subscribers Premises

Double Remote Unit

DRU

Introduction of double remote unit

Subscriber Access Method

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11Overview of PSTN

Technology specific.- Alcatel- OCB283- RU-RSU(1-4K)& DRU - CNE(0.25K)- Siemens- EWSD- RU- RDLU(1.7K)& DRU - not available- Lucent- 5ESS- RU-RISLU & DRU- Not available

Problems with remote/double remote

Working on proprietary protocols Inter-working not possible

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12Overview of PSTN

Use of V5.2 in access network

DLCa/b

ISDNBA

BTS

BSC

V5.2

V5.2 LE

DSLAM

INTERNET

V5.2

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13Overview of PSTN

Open protocol - LE & AN can be of different make - for LE access becomes transparent Subscriber Loop Access on - Wireless - CorDECT, Cellular - Optical Fibre DLC - Copper- 2Mbps -DLC A message based Five Control Protocol Subscriber signals multiplexed in one or more communication

channels

V5.2 Protocol

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14Overview of PSTN

Local Network Structure

ExchangeArea 5

ExchangeArea 4

ExchangeArea 3

ExchangeArea 2Exchange

Area 1

WireCenter

A

WireCenter

B

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15Overview of PSTN

Gateway Switch

Hierarchy of Switches

Gateway Switch

Trunk Automatic Exchange

Trunk Automatic Exchange

Tandem Exchange

Tandem Exchange

Tandem Exchange

Trunk Automatic Exchange

Tandem Exchange

Local Exchange

Local Exchange

Local Exchange

Local Exchange

Local Exchange

Local Exchange

Class 1

Class 2 &3

Class 4

Class 5

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16Overview of PSTN

Hierarchy of Switches

Class 1 - Regional Centre (RC). - "last resort" for final set-up of calls when routes between centres lower in the hierarchy were not available Class 2 - Sectional Centre (SC). - typically connected major toll centres within one/two states Class 3 - Tandem exchanges - connecting major population centres within particular region of the network Class 4 - Tandem exchanges - connecting various areas of a city/towns in a region Class 5 Local Exchanges - subscribers and end-users telephone lines connected

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Tandem ExchangeLocal Exchange

Local Exchange

SwitchingSystems

Inter-exchangeTrunks

Local Loop

Local Loop

LocalLong Distance

NLD POPTAX

Typical Exchange Network

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18Overview of PSTN

Multiple Carrier Network

NLD1

NLD2

NLD3

Region xLong Distance

CarriersRegion y

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19Overview of PSTN

International Network

ILD1

ILD2

ILD3

Country xInternational

Carriers Country y

INT Gateway

INT Gateway

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20Overview of PSTN

23 NLDOs & 18 ILDOs licensed to operate

Long Distance Operators

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21Overview of PSTN

Network Evolution

Earlier Networks (Up to early 70s) - Aanalogue telephone network - Frequency-division multiplexing Present - Local loop analogue - Network digital (based on TDM) Network Migration - IP based switching technology (packet switching, Soft switches, VoIP)

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22Overview of PSTN

NT Switching Systems

OCB 283 ALCATEL (France)

EWSD SIEMENS (Germany)

FETEX 150 FUJITSU (Japan)

5ESS AT&T (U.S.)

AXE10 ERICSSON (Sweden)

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23Overview of PSTN

General Architecture of Exchange

C2 C1Subscriber Access

Switching Network

From another Telephone exchange

Trunks Access

To another subscriber or

Telephone Exchange

N/W controller

Control Unit(Call Processing)

O&M Unit(Control Processing

Programs)

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24Overview of PSTN

PSTN switch (Exchange)

Subscriber interfacing equipment provides access to the customer Trunk interfacing equipment provide access for incoming calls from other

exchanges Switching Network provides path for through connection Control unit, does the call processing control and charging function

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Subscriber Facilities

Analogue subscribers facilities Digital subscribers facilities

Bearer services 64kbps circuit switching Circuit switching in 300 bps-3.4 kbps

Teleservices Supplementary services

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O&M Function Management/ supervision of incidents Supervision of operation Management of charges and deductions Monitoring of exchange performance Security mechanism

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27Overview of PSTN

NTSS:O & M Function

Management/ supervision of incidents Monitoring complaints Automatic testing of lines & circuits Display of alarms Precise location of faults Call statistics

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NTSS:O & M Function Supervision of operation

Subscribers file Groups Additional services Subscriber Equipment Exchange command Translation, routing Charging No. 7 signalling

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29Overview of PSTN

NTSS:O & M Function Management of charges and of deductions

LAMA/ CAMA, Domestic meters, Detailed billing, Centralization of accounts, Coin box , time zones, etc.

LAMA-Local automatic message accountingCAMA-Centralised automatic message accounting

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NTSS:O & M Function

Monitoring of exchange performanceTrafficSubscriber linesConsistency of charging data

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NTSS:O & M Function Security mechanism:

Passwords for workstations and for the operator Non-authorized entry detection

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PSTN Numbering Scheme ITU standard E.164 Numbering format E.164 - Country code, Area code and Phone number International public telecommunication number for geographic areas

(maximum 15 digits) Generally International Numbers limited to 12 digits and National Numbers to

10 digits

- Country code- National Destination code (optional)- Subscriber Number

In India PSTN follows SDCA code+Subscriber Number (10 digit)

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SUMMARY

Public Switched Network External and Internal elements of PSTN Hierarchy of Switches Different classes of PSTN switchLong Distance (Toll)Network Routing diagram for Long distance calls.PSTN N/W and Components Network evolution General architecture of PSTN-- NT switch.

Slide 1Slide 2Public Switched Telephone NetworkTypical NetworkPublic Switched NetworkCustomer Premise Equipment (CPE)Slide 7External Plant Cable NetworkSlide 9Subscriber Access MethodTechnology specific. Alcatel- OCB283- RU-RSU(1-4K)& DRU - CNE(0.25K) Siemens- EWSD- RU- RDLU(1.7K)& DRU - not available Lucent- 5ESS- RU-RISLU & DRU- Not availableUse of V5.2 in access networkOpen protocol - LE & AN can be of different make - for LE access becomes transparent Subscriber Loop Access on - Wireless - CorDECT, Cellular - Optical Fibre DLC - Copper- 2Mbps -DLC A message based Five Control Protocol Subscriber signals multiplexed in one or more communication channelsLocal Network StructureSlide 15Slide 16Slide 17Multiple Carrier NetworkInternational NetworkSlide 20Network EvolutionSlide 22Slide 23PSTN switch (Exchange)Subscriber FacilitiesO&M FunctionNTSS:O & M FunctionSlide 28Slide 29Slide 30Slide 31PSTN Numbering SchemeSlide 33