Synchronization In Telecom Networks

Presented By: Syndicate-2 Aditya Soumava Sheetal Laad Piyush Gupta Rangoli Singhal Mitul Patel

IntroductionSynchronization in telecommunications

networks is the process of aligning the time scales of transmission and switching equipment so equipment operations occur at the correct time and in the correct order.

Contd..Telecommunications’ reliability is based on

the data signals being synchronized and clocked using the same clock everywhere in the network.

The basic clock in the European telecommunications networks (the SDH networks) is called E1, and it must be exactly 2.048 MHz.

Components Of Synchronization Networks

Primary reference clock(PRC)Synchronization Supply Unit (SSU)SDH equipment clock(SEC)

How the clock works

Clock hierarchy

Stratum 1,PRS /g.811,PRC

Stratum-2 or 2E/G.812

Stratum-3 or 3E/G.813

ITU-T SDH Timing Distribution hierarchy

Synchronization Hierarchy with GPRS receivers for SDH transmission

Accuracy of clocks

• Value : 1 part in 10^11PRC

• Value : 1 part in 10^9SSU

• Value : 4.6 part in 10^6SSE

Asynchronous Transfer Mode(ATM)It is a cell-based switching technique that

uses asynchronous time division multiplexing.

It encodes data into small fixed-sized cells.

ATM requires connections to be established before any communication takes place.

Contd..ATM packets are small and have a fixed size

– Packets in ATM are called cells– Small packets are good for voice and video transmissions

Asynchronous Transfer Mode (ATM)

MUX

`

Wasted bandwidth

ATM

TDM

4 3 2 1 4 3 2 1 4 3 2 1

4 3 1 3 2 2 1

VoiceData packetsImages

ATM Cells

The ATM Reference Model

Physical LayerPhysical Medium Dependent[PMD] sublayer Transmission Convergence[TC] sublayer.

ATM Layer

ATM Adaptation Layers (AAL)AAL – 1 to AAL - 5

Applications of ATMReal-time services

Constant bit rate – uncompressed audio/video info Videoconferencing, TV, pay-per-view, VOD, etc.

rt-Variable bit rateNon-real-time services

nrt-VBR – high end system QoS, critical response time Bank transactions, airline reservations, etc.

Unspecified bit rate – best-effort service e.g. text/image messaging, telecommuting

Available bit rate – bursty apps requiring reliable end-to-end connection e.g. LAN, router-to-router reliability

ATM AdvantagesUniversality

Mixed traffic types, real-time and non-real-timeScalability

LANs, MANs, WANs, WLANsEfficient use of network resources Bandwidth

on demand conceptSimplified network infrastructure