SDH & PDH Fundamental

8/9/2019 SDH & PDH Fundamental

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SDH & PDH FundamentalSDH & PDH Fundamental

BY

Chief Engineer NEAMA AWAD JASIMHead of North West Communication Dept.

Ministry of Electricity / Iraq

SDH & PDH Fundamentalby

Chief Engineer neamah awad jasimHead of communication dept. in north west region

the general doctorate of control & operation

Ministry of Electricity IRAQ

[email protected]

please see my whole profile at the URL :

830/56/a50jasim/-awad-https://www.linkedin.com/pub/neamah

Or my page at the facebook:

https://www.facebook.com/neamah.jasim


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PrefaceHi guys, this slide show is basically depend on 2-week training course which i

have been done for teenager engineers & technicians in my dept. in

mosul/iraq. In deed i`m not so much satisfied about some articles in this

show that I left most of my draft paper notes works in my office after i`ve

leaved my city Mosul after the disaster of 10/6/2014 , so I ask my

readers the forgiveness for the lack in this work. But by other hand I hope

that this work will gave a basic background knowledge about this

revolutionary technology in the world of communication. Also I think that

some explanations should be added to some items , but I hope in future

to cover this issues in the next works . Most of graphs in this show have

been made personally depending on the available resources in the web as

mention in the next page .

For more information or any remarks about this work kindly you may mailing

@gmail.com70neamame via

.

The references :1-ALSTOM GRID e-DXC SDH MANUALS

2- The Fundamentals of SDH by Telecommunications Techniques Corporation

(www.ttc.com)

)3- The Fundamentals of SDH-slide show by ( ERICSSON CO.

4- PDH & SDH Integration FOX 515-slide show by ABB CO.

5- Synchronous Digital Hierarchy slide show BY (ABB CO.)

6- SDH Telecommunications Standard Primer by (Tektronix Co.)

7- Course 13 SDH/SONET multiplexing strategy

8- SDH Next Generation by Jos M. Caballero9- Optical Fiber introduction by Patrick LANNUZEL (ALSTOM GRID CO.)

10- SDH Training document BY SEIMENS CO.

11- Synchronous Digital Hierarchy (SDH) Graphical Overview BY CISCO SYSTEMS

12- Synchronous Digital Hierarchy BY 2013 JDS Uniphase Corporation

13- WandelGoltermann_sdh1 REFERENCE BOOK

) BY the author at URL: )-14

8107http://www.kutub.info/library/book/

15- What is SDH ? By RAD data communication systems

16- Wikipedia .com


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6.7

MULTIPLEXINGMULTIPLEXING

Whenever the bandwidth of a medium linking twoWhenever the bandwidth of a medium linking two

devices is greater than the bandwidth needs of thedevices is greater than the bandwidth needs of the

devices, the link can be shared. Multiplexing is the setdevices, the link can be shared. Multiplexing is the set

of techniques that allows the (simultaneous)of techniques that allows the (simultaneous)

transmission of multiple signals across a single datatransmission of multiple signals across a single data

link. As data and telecommunications use increases, solink. As data and telecommunications use increases, so

does traffic.does traffic.

Frequency-Division Multiplexing (FDM)

Wavelength-Division Multiplexing (WDM)

Time-Division Multiplexing (TDM)

TYPES OF MULTIPLEXINGTYPES OF MULTIPLEXING


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1-Frequency Division Multiplexing (FDM)

Looking to the past :The Analog HierarchyIt was Using the FDM Transmission technology at old

fashion Telephony systems


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2-Wave length Division Multiplexing (WDM)

this method used the same channel or media but with manydifferent wavelength optic signals , it is used mainly with

fiber optics communication at very high rate levels.

OPGW stand for FIBER OPTIC OVERHEAD

GROUND WIRE

the usable band of light that used in fiber optic

communication


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High Density WDM (DWDM)

The Digital Transmission of Information


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THE PULSE CODE MODULATION (PCM) PRINCEBLEEach sample of analog signal represent by a digital code

i.e.;PAM.PPM.PDM..ETC.


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According to the Law FS 2W (Nyguist law)Where FS is Sampling frequency & W is the common bandwidth of Human

Sound (4KHz) Thin FS= 2*4= 8 KHZ 8000 sample / sec.

Each sample represent by

8-bit then 2 EXP 2 = 128

level & as the Sound is

alternative signal so it

should be 128

Quantization Levels in each

direction


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3-Time Division Multiplexing (TDM)

TDM is a digital multiplexing technique for combiningseveral low-rate digital channels into one high-rate one.

This method of Multiplexing mainly used with PDH

Hierarchies T1& E1

Time Division Multiplexing Bit

Interleaving This method ofMultiplexing mainly used

with PDH

Hierarchies T1& E1


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Plesiosynchronous Multiplexer use bit interleavedMechanism due that the incoming signal bits came in different

width or periods so the MUX.add some justification bits (Mappingmethod) to get the synchronization of different rate tributaries of

the incoming steams.

InterleavingThe process of taking a group of bits from each input line for

multiplexing is called interleaving. We interleave bits (1 - n)

from each input onto one output.


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This method used

in SDH & S0NET

Time Division Multiplexing Byte

Interleaving This method usedin SDH & S0NET

Byte interleaving takes advantage of technology

develo ed for com uters and reserves b te timin

SSSynchronization


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Synchronization Pattern or

Framing bits( This Technique used in American PDH

Hierarchy standard T1 While in European

standard there are a channel for this purposes)

The Communication Era before SDHThe development of digital transmission systems started In the early70s , and was based on the Pulse Code Modulation (PCM) method.

In the early 80's digital systems became more and more complex , yetthere was huge demand for some features that were not supportedby the existing systems. The demand was mainly to high ordermultiplexing through a hierarchy of increasing bit rates up to 140Mbps or 565 Mbps in Europe. The problem was the high cost ofbandwidth and digital devices. The solution that wascreated then , was a multiplexing technique , allowed for thecombining of slightly non synchronous rates, referred to as

plesiochronous*, which lead to the term plesiochronous digitalhierarchy (PDH).

*plesiochronous - "almost synchronous , because bits are stuffed intothe frames as padding and the calls location varies slightly - jitters -from frame to frame".


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The Most Common PDH Hierarchies

1-The American standard of digital transmission ( T1)


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This standard used Mainlyin north America & in

Japan with some

modifications

T-1 line for multiplexing telephone lines

T-1 frame structure


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Digital hierarchy

The Most Common PDH Hierarchies2-The European Standard (E1)This standard used in Europe & other world Countries


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This Happen when

we used the

channels for data

only not for speech


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The PDH Standards in the World

PDH Add(Insert)/Drop Functionby

Stepper MULTIPLEXING/DEMULTIPLEXING

EASTWEST

LTE :LINE TERMINAL

EQUIBMENT


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TheAdd/ Drop Scheme regard as the main disadvantage scheme of

PDH compare with SDH that there is ability to add(insert)/ drop

different rates of Tributaries along the a path while in PDH it

should be multiplex/demultiplex till to reach the appropriate lower

rate carrier

SDH (Synchronous Digital Hierarchy)

IS AN ITU-T STANDARD FOR A HIGH CAPACITY TELECOM NETWORK.

SDH IS A SYNCHRONOUS DIGITAL TRANSPORT

SYSTEM, AIM TO PROVIDE A SIMPLE, ECONOMICAL

AND FLEXIBLE TELECOM INFRASTRUCTURE .ATTEMPTS TO FORMULATE

STANDARDS FOR TRANSMISSION OF SYNCHRONOUS SIGNALS

BEGAN IN U.S. AT THE BEGINNING OF 1984, BY ANSI ACCREDITED

T1X1 COMMITTEE.IN 1985 SONET STANDARD WAS BORN.IN 1986

CCITT BECAME INTERESTED IN SONET STANDARD.CCITT PROPOSED

CHANGES TO T1X1COMMITTEE TO ACCOMMODATE BOTH

AMERICAN AND EUROPEAN HIERARCHIES. FINAL AGREEMENT WAS

REACHED IN 1988 AND CCITT WORKING GROUP-XVIII CAME OUT

WITH RECOMMENDATIONS ON SDH


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SDH (Synchronous DigitalHierarchy)so SDH is an international standard for high speedtelecommunication over optical/electical networkswhich can transport digital signalsin variable capacities. It is a synchronous systemwhich intend to provide a more flexible , yet simplenetwork infrastructure.

SDH (and its American variant- SONET) emerged from

standard bodies somewhere around 1990.these two standards create a revolution in the

communication networks based on opticalinfibers their costandperformance.

why using SDH ?Although PDH was A breakthrough in the digital transmissionsystems , it has a lot ofweaknesses :

- No world standard on digital format (three incompatibleregional standards - European, North American andJapanese).

- No world standard for optical interfaces. Networking isimpossible at the optical level.

- Rigid asynchronous multiplexing structure.

- Limited management capability.

- Because of PDH disadvantages, It was obvious That a newmultiplexing method is needed.The new method was called SDH.


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SDH has a lot of advantages

First world standard in digital format.

First optical Interfaces.

Transversal compatibility reduces networking cost.Multivendor environment drives price down

Flexible synchronous multiplexing structure .

Easy and cost-efficient traffic add-and-drop and cross connectcapability.

Reduced number of back-to-back interfaces improve networkreliability and serviceability.

Powerful management capability.New network architecture. Highly flexible and survivable selfhealing rings available.

Backward and forward compatibility: Backward compatibilityto existing PDHForward compatibility to future B-ISDN, etc.

Standards of SDH

SDH has been standardized by ITU-T in 1988.

In November 1988 the first SDH standards were approved.

In 1989 , the CCITT (International Consultative Committee on Telephony & Telegraphy)had published in its "Blue book" recommendations G.707 , G.708 & G.709 coveringthe SDH standards.

G.702 - Digital Hierarchy Bit RatesG.703 - Physical/Electrical Characteristics of Hierarchical Digital

Interfaces

G.707 - SDH Bit RatesG.708 - Network Node Interface for the SDHG.709 - Synchronous Multiplexing StructureG.773 - Protocol Suites for Q Interfaces for Management of

Transmission SystemsG.781 - (Formerly G.smux-1) Structure of Recommendations on

Multiplexing Equipment for the SDHG.782 - (Formerly G.smux-2) Types and General Characteristics

of SDH Multiplexing EquipmentG.783 - (Formerly G.smux-3) Characteristics of SDH Multiplexing

Equipment Functional BlocksG.784 - (Formerly Gsmux-4) SDH Management


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Compare between SDH & SONET speed

rates

SONET &SDH are almost the same, but the SONET for American standard ,Japan and SDH for

Europe & rest of the world

SDH Hierarchy compare with SONET


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2.175mb/s

The SDH have some version according to the needs of

customers


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Elements of SDH Multiplexing

1- The Containers C

The Container (C)

Basic packaging unit for tributary signals (PDH)

Synchronous to the STM-1

Bitrate adaptation is done via a positive stuffing

procedure

Adaptation of synchronous tributaries by fixedstuffing bits

Bit by bit stuffing

OR Container-n( n=1-4 ): is the information structure

which forms the network synchronous information

payload for a virtual container


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2-Virtual Containers VC

The Virtual Container (VC)

Formation of the Container by adding of a POH

(Path Overhead)

Transport as a unit through the network (SDH)

A VC containing several VCs has also a pointer area

Virtual Container-n(VC-n):It is the informationstructure used to support path layer connections in

the SDH. There are Two types of VCs: Lower order

VC-n(n=1,2) & Higher order Vc-n(n=3,4)


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Virtual Containers(VC)

The Virtual Container is obtained after adding POH to The

Containers


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3-Administrative Units (AU)

It is an information structure which provides adaptation

between two

layers: -Between lower and higher order path layers for TU

-Between higher order path layer and section layer for AU

4-Tributary Unit (TU)


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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 atlast

The Synchronous Transport Module Level 1 (STM- 1)

Formed by adding a Section Overhead (SOH) to AUs

Clock justification through positive-zero-negativestuffing

in the AU pointer area

byte by byte stuffing

Structure of the administrative units and of the

tributary units used in the SDH system


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5-Tributary Unit Group (TUG)

6-Adminstrative Unit Group (AUG)


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7-Path Over Head (POH)

1-High Order Path Over Head(HO-POH)

Used with VC-3/VC-4

2-Low Order Path Over Head (LO-POH)

Used with VC-11/VC-12

High Order(H0) &Low Order(LO)

POH & Related Containers


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LO-POH have two forms

The Mapping process in SDH system

(HO-POH) have also two forms


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HO-POHit is the 10 columns of the STM-1 Structure ,

consist of 9 bytes determine the boundaries of VC-4

Details of J1 & B3 of Higher Order POH J1 - Higher-Order VC-N path trace byte

This user-programmable byte repetitively transmits a 15-byte string

plus 1-byte CRC-7. A 64-byte free-format string is also permitted for

this Access Point Identifier. This allows the receiving terminal in a

path to verify its continued connection to the intended transmitting

terminal.

B3 - Path Bit Interleaved Parity code (Path BIP-8) byte

This is an even-parity code, used to determine if a transmissionerror has occurred over a path. Its value is calculated over all the

bits of the previous virtual container before scrambling and placed in

the B3 byte of the current frame. (BIP-8 is calculated on the 8 bit

blocks of the nth frame and placed on the (n+1) the frame of VC3/

VC4.)

C2 - Path signal label byte This byte specifies whether the virtualcontainer is equipped or not and the mapping type in therespective virtual container.


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What is BIP?

Bit Interleaved Parity

Error monitoring in SDH uses a CRC with a

polynomial, xn+x0, called Bit Interleaved Parity (BIP-

n).

The signal to be monitored is divided in to small

blocks with n-bit size. The even parity check is

applied to each bit of all the blocks in the signal, fro

m 1st to nth bit independently.


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Used with C-4 /C-3


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Comparison of POH in Higher and Lower

Orders


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8-Pointers is an indicator whose value defines theframe offset of a VC with respect to the frame reference of

the transport entity on which it is supported .

The Role of AU-Pointers in SDH system, is performing AU

units in Process called Adaption OR Aligning

the rest of AU-MATRIX is commonly filled with stuffing or

justification bits .Also AU- pointer determine the starting of

pay load or VC within the STM structure .

The pointer consist of three bytes (H1,H2,H3) as

follows :


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Application of Pointer A Pointer is used to address a particular locationwithin an AU or a TU structure. There are mainly 2

types of pointers

1. AU Pointers: used to point at Higher Order VCs (VC-4,3) in

an STM frame

2. TU Pointers: used to point at Lower Order VCs (VC-12) in

higher order VC

Each of these pointers carry the offset number (address) at

which the 1st byte of the payload is located, within the frame.The offset numbering of AU4, TU3, TU12, frames are shown

in slide # 66, 68, 71. The offset numbering of TUs/AUs will be

according to the CCITT Rec. G.707.

Functions of a Pointer1. Minimization of multiplexing Delay

This is the main advantage of pointers. Normally signals from different originatingpoints differ in theirphases, because of different transmission length and

different clock generation. In the usual multiplexing process, to align them, eachsignal has to be written into memories and read out using a

new phase of the frame to be multiplexed. Thus, it is inevitable to cause additionaldelay of half of theframe time in average and one frame time at maximum. Also,

it requires large capacity memories.

To avoid above inconveniences, this pointer method was introduced into themultiplexing of SDH signal. A pointer is assigned to each VC to be multiplexed andit indicates relative phase shift between the VC and the new frame by using theaddress number in the new frame. As a matter of course, every VC

has different pointer value. The pointer is renewed at every multiplexing process, soit is not necessary to introduce undesirable additional delays.

arrival speed


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What is Justification Imagine 2 compartments of a train. It is connected with

a pair of buffers and flexible chain.

If the first moving compartment going faster the next.

The chain will pull the next compartment. This is

equivalent to Positive Justification.

If the first compartment is moving slower than the next

the buffers will collide and slow down the next one. This

is equivalent to Negative Justification.

In this example, the first moving compartment is

analogous to higher order tributary and the next is

equivalent to primary tributary.

Effects of Justification Assume secondary tributary speed fs

Assume primary tributary speed fp

If fs > fp, Positive Justification, the effect will be to read one

information bit of primary as two information bits of secondary.

Hence, in secondary one bit has to be inhibited.

If fs < fp, Negative Justification, the effect will be to lose one

information bit of primary in the secondary. Hence, in secondaryone bit has to be introduced.

If fs = fp, Zero Justification, the ideal situation but difficult torealize in practice.

In SDH, all the above 3 justifications will be achieved byintroduction of a pointer in addition to the information andpath overhead bits


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Positive justification

Negative justification


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Mu tip exing steps o 2M s E1 into

STM-1 SignalDue that there are multi rate tributaries like (ATM,GFP(2.114Mb/s)or the rate of E1signal (2.048Mb/s) is not always in regular speed so the concept of multi-frame isintroduced for the convenience of rate adaptation used in multiplexing 2Mb/sinto STM-1signal , i.e. four C-12 basic frames form a multi-frame , each basic C-12frame represent by 94-2 matrix (notched matrix )

Since the frame frequency of the C-12 basic frame is 8000-frame per second, theframe frequency of the C-12 multi-frame will be 2000-frame per second.

-if E1 signals have a standard rate of 2.048Mb/s, each basic frame willaccommodate 32-byte (256-bit) which a integer value.

--- While when E1 signals rate of 2.046Mb/s are accommodated into a C-12 basicframe, the average number of bits loaded in each frame is: (2.046 x106b/second)/(8000-frame/second)=255.75 bits. Because this number is not an

integer so if a multi-frame of four basic frames is used, the number of bits can beloaded in the multi-frame is: (2.046 x 106b/second)/(2000-frame/second)=1023

bits. Each of the first three basic frames accommodates 256-bit (32-byte) payloadand the fourth accommodates 255-bit payload.

--A multi-frame can accommodate payloads at the rate ranging from C-12 Multiframe max to C-12 Multi-frame min, as follows:

C-12 Multi-frame max=(1023+1+1)x 2000=2.050Mb/s

C-12 Multi-frame min=(1023+0+0)x 2000=2.046Mb/s while

Mapping 2M to THE SDH streamFirst step is mapping E1 signal into SDH Container (creating

containers) ,


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C-12 Containers as in each of tow

ma in methods


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Multiplexing steps (E1 to STM-1)

First step is mapping E1 signal into SDH Container (creating Containers)

E1 PDH stream is interleaved into multi frame stream

1-Creating C-12 multi framethe regular rate of E1 signal is 2.o48Mb/s & the Max`m rate of C-12 is (2.176Mb/s)

So that each basic C-12 can handle the maximum rate of E1


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The rest of C-12 Used AS Overhead for E1 AS follows

2-Creation of VC-12 Multi frameTo monitor on a real-time basis the performance of each 2Mb/spath signal during transmission on SDH network, C-12 mustbe further packed ---- adding corresponding path overhead(lower order overhead)---- to form a VC-12 informationstructure. the LP-POH (lower order path overhead) is addedto the notch in the top left corner of each basic frame. Eachmulti-frame has a set of lower order path overhead

composed of total 4 bytes: V5, J2, N2 and K4. Since the VCcan be regarded as an independent entity, dispatching of2Mb/s services later is conducted in unit of VC-12.

A set of path overhead monitors the transmission status of thewhole multi-frame on a network. How many frames of 2Mb/ssignals does a C-12 multi-frame accommodate? One C-12multi-frame accommodates 4 frames of PCM30/32 signals.Therefore a set of LP-POH monitors the transmission status of4 frames of PCM30/32 signals.


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3-Creation of TU-12 Multi frame

For correct aligning of VC-12 frames in the receiving end, a four-byteTU-PTR (Pointer)is added to the four notches of the VC-12 multi-

frame. Then the information structure of the signal changes into TU-

12 with 9 rows x 4 columns. The TU-PTR indicates the specific

location of the start point of the first VC-12 within the multi-

frame.The First two pointers used for these purposes.

The Structure of VC-12 POH


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The construction of TU-12 multi frame


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4-Creation of tributary Unit group-2

Three TU-12 forms a TUG-2 via byte interleaved multiplexing. TheTUG-2 has the frame structure of 9 rows by 12 columns .

So ,According to (Rec. G.709)TUG-2 Unification lowrate tributaries belong to US,CEPT Standards Like

E1(C-12),T1(C11), T2..etc.


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5-Creation of Tributary Unit Group -3

(TUG-3)Seven TUG-2 can be multiplexed into a TUG-3 information

structure via byte interleaved multiplexing. Note that this

information structure formed by the 7 x TUG-2 is 9-row by

84-column. Two rows of fixed stuff bits shall be added in

front of the structure, as illustrated in slide -------- . The

multiplexing structure for the TUG-2 via the TUG-3 is

depicted in slides ------ . The TUG-3 is a 9-row by 86-

column structure with the first two columns of fixed stuff.

5-Creation of TUG-3


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In the first column of the TUG3 unit there are reserved positions for the

VC3 pointer due to the fact that it is a fixed phase relation between

the TUG2 and the TUG3 unit it is not necessary a pointer; thepositions for the pointer are occupied by a null pointer indicator (NPI

Null Pointer Indicator).

5-Creation of TUG-3


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5-Creation of TUG-3

Highest multiplexing point has been introduced by SDH to

accommodate high rate European 140 Mbps and to

accommodate lower bit speed tributaries, So,TUG-3 role is

like TUG-2, Unification of High Tributaries of US & CEPT

standards Hierarchies


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Creation of TUG-3

Fixed

Stuffs

The Anatomy of TUG-3 is depend on the rate of tributary So,When we

start with 2Mb/s input then TUG3 became as shown below but if we

start multiplexing with higher rate tributary then this is another story .


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While here


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6- Creation of Container -4 (C-4)Three TUG-3 can be multiplexed into the C-4 signal structure viabyte interleaved multiplexing method. The arrangement ofthree TUG-3s multiplexed in the VC-4. The TUG-3 is a 9-rowby 86-column structure. The VC-4 consists of one column ofVC-4 POH, two columns of fixed stuff and a 258-columnpayload structure. The three TUG-3s are byte interleaved intothe 9-row by 258-column VC-4 payload structure and have a

fixed phase with respect to the VC-4. The phase of the VC-4with respect to the AU-4 is given by the AU-4 pointer.

Since the TUG-3 is an information structure of 9 rows x 86columns, the information structure composed of three TUG-3via byte interleaved multiplexing is a block frame structure of9 rows x 258 columns. While C-4 is a block frame structure of9 rows x 260 columns. Two columns of stuffed bits are addedto the front of the composite structure of 3 x TUG-3 to form aC-4 information structure. shows the frame structure of oneC-4.


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6- Multiplexing of Container -4 (C-4)

7-Creation of Virtual Container -4 by

mapping or adding (HO-POH)


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SDH Section Over Head (SOH) & SSMThese bytes(91 bytes) lies between columns (1 to 9) in the STM-1

structure, each byte of them has particular role like signaling, control

,alarms ,multiplexing demultiplexingetc. , some bytes of them are

media dependent bytes, while others spare for future applications.

They are divided into three parts as follows:

1-Regenerator Section Overhead (RSOH)

2-AU-Pointer

3- Multiplex Section Over Head (MSOH)


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AU Pointer


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AU-4 Pointer

AU-4 Pointer offset numbering


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RSOH

RSOH


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MSOH

8-Multiplexing Administrative Unit-4 (AU-4) with

Regenerator Section Over Head (RSOH)


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9-Multiplexing AUG-1 with Multiplexing

Section Over Head(MSOH)

TU3 Pointer


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10-the last step getting Synchronous Transmission

Module1 (STM-1) by multiplexing MSOH

SDH Signal STM-N (Synchronous Transport

Module)frame structure


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So the structure of STM-1 is look like this blocks

when it multiplexed from C-12 tributary

Thus each STM-1 Containsabout 2M373=632M b/s data


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While The payload of STM-1 with C-4 tributary will be one

single block of data (about 150 Mb/s) , this happen in cases

look like HD video broadcasting etc.

While we have Here the payload of STM-1

With 3 VC-3


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High order of SDH

STM-4


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STM-16


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The Broadband Communication

Architecture

The OSI(Open Source Internetworking) Model


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SDH Layers according to the OSI

model

Logical &Physical network Paths or Layers

in SDH


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Logical &Physical network segments

The Various transport segments in SDH


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Another example of Layers networks in

SDH with different Elements


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The Add And Drop Multiplexer (ADM)The function of (ADM) is to cross multiplex/de-multiplex the low rate tributary signal

(PDH,STM-M) to the High rate STM-N signal in east or west lines & STM-N signalcross connect west or east line port ( M less than N) . Also it include the cross

connect of the STM-N SIGNAL between the sides of the W/E line. ADM is equivalent

to two TMs, ADM is used in transfer stations of SDH network.

The REGENATOR (REG)is used to regenerate the (high rate) STM-N in case that the

distance between two sites is longer than the transmitter can carry.

REG needs only to handle RSOH in the STM-N frame to reproduce the

The STM-N frames.


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Digital Cross- Connect (DXC)

SDH Topologies

1-the chain topology

The linear bus (chain) topology used when there is no need

for protection and the demography of the sites is linear.


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2-Point to Point Topology

3-Point to Multipoint Topology


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4-Hub Topology

5-Ring Topology


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7-The Star topology

is used for connecting far and less important sites

to the network.

Usage of SDH elements in SDH Topologies

The Terminal multiplexer can be used to connect two sites in a high rate connection .

The Add And Drop Multiplexer (ADM) is used to build the chain topologies in the

above picture. At the ends of the chain usually a Terminal Multiplexer is connected.

The Add And Drop Multiplexer (ADM) is used to build the ring topology .AT each site

we have the ability to add & drop certain tributaries.


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SDH ProtectionThe SDH gives the ability to create topologies with protection for the datatransferred. Following are some examples for protected ring topologies.

At this picture we can see Dual

Unidirectional Ring . The normal

data flow is according to ring A

(red). Ring B (blue) carriesunprotected data which is lost

in case of breakdown or it

carries no data at all.

In case of breakdown rings A & B become one ring without

the broken segment.


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The Bi-directional Ring allows data flow in both directions. For

example if data from one of the sites has to reach a site which is next

to the left of the origin site it willflow to the left instead of doing awhole cycle to the right.

In case of breakdown some of the data is lost and the important data

is switched. For example if data from a site should flow to its

destination through the broken segment, it will be switched to the

other side instead.


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Protection Methods

Protection Methods


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Automatic Protection Switching (APS)

Automatic Protection Switching (APS) is the

capability of a transmission system to detect a

failure on a working facility and to switch to a

standby facility to recover the traffic.

This capability has a positive effect on theoverall system availability.

Two modes of APS are provided:

1+1 protection switching

1:N protection switching.


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Another samples of protection switching


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What is in the future

SDH & PDH Fundamental

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Transcript of SDH & PDH Fundamental