SDH Concepts & Principle
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SDH Concepts & Principle
Department of Electronics and Telecommunication
Made by :
Siddharth Shetty (748)
Aditya Vikram Singh(750)
It is an international standard networking principle and a multiplexing method. The name of hierarchy has been taken from the multiplexing method which is synchronous by nature. The evolution of this system will assist in improving the economy of operability and reliability of a digital network.
1. Historical Overview
In February 1988, an agreement was reached at CCITT (now ITU-TS) study group XVIII in Seoul, on set of recommendations, for a synchronous digital hierarchy representing a single world wide standard for transporting the digital signal. These recommendations G-707, G-708, G-709 cover the functional characteristic of the network node interface, i.e. the bit rates and format of the signal passing over the Network Node Interface (NNI).
For smooth transformation from existing PDH, it has to accommodate the three different country standards of PDH developed over a time period. The different standards of PDH are given in Fig.1.
The first attempt to formulate standards for Optical Transmission started in U.S.A. as SONET (Synchronous Optical Network). The aim of these standards was to simplify interconnection between network operators by allowing inter-connection of equipment from different vendors to the extent that compatibility could be achieved. It was achieved by SDH in 1990, when the CCITT accepted the recommendations for physical layer network interface. The SONET hierarchy from 52 Mbit per second rate onwards was accepted for SDH hierarchy (Fig.1).
2. Merits of SDH
(i) Simplified multiplexing/demultiplexing techniques.
(ii) Direct access to lower speed tributaries, without need to multiplex/demultiplex the entire high speed signal.
(iii) Enhanced operations, Administration, Maintenance and provisioning capabilities.
(iv) Easy growth to higher bit rates in step with evolution of transmission technology.
(v) Capable of transporting existing PDH signals.
(vi) Capable of transporting future broadband (ATM) channel bit rates.
(vii) Capable of operating in a multi-vendor and multi-operator environment.
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SDH ppt.pptx (Size: 1.04 MB / Downloads: 94)
Prepared by:Anuj Prabhakar Lakra
SYNCHRONOUS DIGITAL HIERARCHY(SDH)
ITI UNITS IN INDIA
ITI LTD. NAINI
T.E.D. (Transmission Equipment Division)
T.I.D. (Telephone Instrument Division)
R & D (Research & Development)
Administrative Control Division
PDH(Plesiochronous Digital Hierarchy)
Technology used to transfer large amounts of data over fibre optic or microwave band radio's.
Implementation of networks with transmission capacities of up to 140 Mbit/s.
The basic transfer rate of the data is 2048 kilobits per second.
LIMITATIONS IN PDH
There’s no standardised definition of PDH bit rates greater than 140 Mbit/s.
Back to Back multiplexing
Inter Operas Ability of System Between Different Vendors
No optical interfaces world standard and without an optical level, networking is not possible
High Transmission Rates
Simplified Add & Drop Function
High Availability and Capacity Matching
Future Proof Platform for New Services
Advantages of SDH
world standard digital format
cost effective and easy traffic cross connection capacity and add and drop facility
reduced networking cost due to the transversal compatibility
Network resources are synchronised to a master clock.
STM-1 bit rate
The frame having a duration of 125 microseconds corresponds
to a matrix of 9 Rows by 270 x N columns whose elements are
Data are sent line after line, from left to right and top to bottom.
To support 8 KHz sampled voice applications
Bytes organized into rows and columns Administrative channels
are rate decoupled for easier processing
STM-1 frame is organized into 270 (3 x 90) columns by 9 rows
Frame size is 2430 bytes
9 x 270 bytes/frame x 8 bits/byte x 8000 frame/s = 155.52 Mbit/s
Byte-interleaving STM-1 modules
No extra overhead introduced
Overhead of multiplexed signals taken over, but section overhead
(SOH) should be replaced with new information for the STS-N
Overhead is growing in absolute number of bits, but relative size
is the same
New overhead is bigger than necessary for regenerator and
multiplex section overheads, so some bytes are unused
Section overhead (SOH) is frame aligned
SPE (multiplexed VC-3 or VC-4 channels) is not frame
Three levels of Network Protection
Protection in Ring Network
Protection in Meshed Network
SDH in future
The modern lifestyle requires high speed communication applications.
SDH provides large bandwidth that can meet the needs of this applications.
SDH networks have flexible routing ability for circuit protection thus allowing rapid circuit reallocation and high circuit availability.