1SDH Basics

© Tejas Networks India Ltd., 2007, Proprietary Information

SDH Basics


Objective

What is SDH?

SDH System

Standards

Frame Structure

Multiplexing

Advantages


SDH is a timing hierarchy

• Allows higher and more flexible bit-rates than PDH

• Uses a different frame structure and synchronization

Hierarchical synchronization

•One master clock to synchronize whole operator network

What is SDH?????


SDH System

•TERMINAL EQUIPMENT

• REGENERATOR

• ADD / DROP MULTIPLEXER


The hierarchy is as follows:

Optical Signal Bit Rate Abbreviated asSTM-0 51.84 Mbps 51 MbpsSTM-1 155.52 Mbps 155 MbpsSTM- 4 622.080 Mbps 622 MbpsSTM-16 2488.320 Mbps 2.4 GbpsSTM-64 9953.280 Mbps 10 GbpsSTM-256 39813.12 Mbps 40 Gbps

Standards


TX END


RX END


STM-1 Frame Format

9 Rows

Administrative Unit

Capacity of theVirtual Container

+Pointers

1

2

3

4

5

6

7

8

9

RegeneratorSectionOverhead

MultiplexSection

Overhead

H3H1 H2Pointers

STM-1 = 270 Columns (2430 bytes)

H1H1 H1 H2 H2 H2 H3 H3 H3

Frame =125µs Frame = 125µsFrame =125µs

Overhead width = 9 columns


STM-N Frame Format

Frame = 125µs


Frame Format

STM - Section overhead and Administrative unit

Section overhead – Regenerator section overhead and Multiplex section overhead

Administrative unit – Virtual container and pointers

Virtual container - Payload and Path overhead information

1 Byte=8bits * 8000 frames/sec=64 Kbps

Payload

STM-N

Administrative unit

Pointer Virtual Container

Path overhead

Section Overhead

Regenerator Overhead

Multiplex overhead


The Container (C)– Basic packaging unit for tributary signals (PDH)


The Virtual Container (VC)– Formation of the Container by adding of a POH (Path Overhead)

The Tributary Unit (TU)– Is formed via adding a pointer to the VC

The Tributary Unit Group (TUG)– Combines several TUs for a new VC


The Administrative Unit (AU)– Is shaped if a pointer is allocated to the VC formed at last

The Syncronous Transport Module (STM-N)– Formed by adding a Section Overhead (SOH) to AUs


SDH Multiplexing


SDH Multiplexing

9 X 261

743 6521 743 6521 743 6521

321

4321 9 rows

4 columns

TUG-2 9 X 12

TU – 12 9X4

TUG-3 9 X 84

POH

POH

POH

Stuffing and POH

TUG - 3TUG - 3TUG - 3

Section Over Head

(9 X 9)


Advantages

High speed standards Efficient Multiplexing / Demultiplexing Enhanced Operation, administration, Provisioning, Maintenance

capabilities (OAM&P)A reduction in the amount of equipment .The provision of overhead and payload bytes Synchronous multiplexing format for carrying lower-level digital signals is

justified.The availability of a set of generic standards, which enable multi-vendor

interoperability.


Thank You…

1SDH Basics

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