4 Multiplexing hierarchy The PDH high capacity transmission networks are based on a hierarchy of digital multiplexed signals: E.1 to E.4.The basic building block is the primary rate of Mb/s (E.1). This could be made up of 30 x 64 Kb/s voice channels. This would then be multiplexed up to a higher rate for high capacity transmisson.
5 Four signals at the primary rate can be multiplexed up to the secondary rate, E.2, of Mb/s and so on up to a rate of 139 Mb/s (E.4).Thus the 139 Mb/s rate represents 64 x Mb/s signals and 1920 multiplexed voice channels.
6 Developing networksThe plesynchronous multiplexing technology, often called PDH (Plesiochronous Digital Hierarchy), left no room in the signal structures for network management and maintenance functions.We are therefore left with no spare signal capacity to provide improvements in the signal transmission.
7 As networks developed inter-connection became increasingly complex As networks developed inter-connection became increasingly complex. It required banks of multiplexers and large, unreliable distribution frames.It became clear that the original standards, designed for point-to-point links, were just not suitable.
9 Tributary accessWe want to have easy access to an individual tributary, in order that it may be re-routed.We cannot do this without having to demultiplex the whole signal down to the required tributary level.Costs go up as we demultiplex, and they then double because we have to re-multiplex the signal back up again.
10 No commont standardBefore SDH there were no standards to ensure that equipment from different vendors interworked on the same system.Vendors can have their own unique designs which means we have to buy the same vendor’s equipment for both ends of the line.Ideally we would like to shop around for the most suitable equipment, without having to keep to the same supplier.
11 What we needNetwork operating companies have to provide faster, cost effective provisioning of customer circuits and services, as well as control of transmission bandwidth.
12 SDH DefinitionSDH is a standard for ‘high speed – high capacity’ optical telecommunication networks ; more spesifically a synchronous digital hierarchy.It is a synchronous digital transport system aimed at providing a more simple, economic and flexible telecommunications network infrastructure.
13 Advantages of SDHDesigned for cost effective, flexible telecoms networking – based on direct synchronous multiplexing.Provides built-in signal capacity for advanced network management and maintenance capabilities.
14 Provides flexible signal transportation capabilities – designed for existing and future signals. Allows a single telecommunication network infrastructure – interconnects network equipment from different vendors
15 Where is SDH used ?SDH can be used in all of the traditional network application areas.A single SDH network infrastructure is therefore possible which provides an efficient direct interconnection between the three major telecommunication networks.
16 Notes on SDH ratesThe most common SDH line rates in use today are Mbps, Mbps, 2.5 Gbps, 10 Gbps.SDH is a structure that is designed for the future, ensuring that higher line rates can be added when required.
17 SDH signal structureThe SDH signal is transported as a synchronous structure which comprises a set of 8-bit bytes organised into a two dimensional frame.The ‘Truck analogy’ is a popular way to help us understand the contents of the SDH frame.
18 SDH FRAME STRUCTURETRUCK ANALOGYPayload UnitTractor Unit
20 The PayloadThe contents of the container carried by the truck represent the real value.This ‘Payload’ is analogous to customer traffic, being carried by the ‘container’ within an SDH frame.This Payload ‘container’ supports the transportation of spesific tributary signals.
21 The Section OverheadWhat actually gets the contentsof the truck to it’s destination is the tractor unit.This analogous to the network maintenance and management capability carried by the SDH frame, known as it’s Section OverHead, or SOH.
22 The Section Overhead (SOH) provides facilities that are required to support and maintain the transportation of customer traffic Safely across the network.THE SOH is split into Multiplexer Section Overhead (MSOH) and Regenerator Section Overhead (RSOH).
23 The Virtual ContainerEven if the container is loaded on to a different truck, there is a portion of overhead that always remains with it.This is known as the Path OverHead, or POH.The Path Overhead is directly associated with the payload capacity area, and together they form what’s known as the Virtual Container.
24 SDH FRAME STRUCTURE STM-N FRAME STRUCTURE 270 x N Columns = 8 bits/byte9 Rows261 x N Columns9 x N Columns
25 SDH FRAME STRUCTURE signal frame transmission The principle for SDH signal frame transmission is: the bytes (8-bit) within the frame structure is transmitted byte-by-byte (bit-by-bit) from left to right and from top to bottom. After one row is transmitted, the next row will follow. After one frame is completed, the next frame will start
26 SDH FRAME STRUCTURE SDH Rate ITU-T defines the frequency to be 8000 frames per second for all levels in STM hierarchySTM-1 Rate :9 rows x 270 columns x 8 bits/byte x 8000 frames per second= Mb/sSTM-4 Rate :9 rows x (270 x 4) columns x 8 bits/byte x 8000 frames per second= 622 Mb/s
34 SDH Tributary Multiplexing (2M) ×3112TUG-29×7RTUG-386MultiplexingSame as for C3Multiplexing route: 1X2M 3XTU12 7XTUG-2 3XTUG-3 1XSTM-1--- One STM-1 can load 3X7X3 = 63X2M SignalsMultiplexing structure: structure此页标题禁止有多级标题，更不要出现所在章节的名称。此页标题要简练，能直接表达出本页的内容。内容页可以除标题外的任何版式，如图、表等。该页在授课和胶片＋注释中都要使用。
35 SDH Network protection Bidirectional TrafficTraffic flow direction along the ringClockwise or counter-clockwisUnidirectional TrafficTraffic flow direction along the ringClockwise and counter-clockwise
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