SDH Principle

BASIC PRINCIPLE

SDH

1 、 SDH Basic Concept

2 、 Frame Structure And SOH

3 、 Multiplexing And Mapping

4 、 Synchronous Multiplexing System

5 、 SDH Self-healing Network

6 、 Clock And Timing

Summary

SDH Basic Concept

1 、 PDH Disadvantage — Lack of international uniform rate

2M Series ： 2M 、 8M 、 34M 、 140M 、 565M ； 1.5M Series ： North American ： 1.5M 、 6.3M 、 45M 、 274M

Japan ： 1.5M 、 6.3M 、 32M 、 100M ； — Lack of international uniform optical interface standard

—Add/Drop Service need a count of hardware and the Structure is complicated

— Multiplexing/De-Multiplexing need hardware step by step

— Network OAM&P capability is faultiness

SDH Basic Concept

400Mb/s

100Mb/s

32Mb/s

6.3Mb/s

series ofJapan

274Mb/s

45Mb/s

6.3Mb/s

565Mb/s

139Mb/s

34Mb/s

8Mb/s

2 Mb/s 1.5Mb/s

series of North America

series ofEurope

×4 ×4

×4

×4

×4

×4

×3

×5

×6

×7

×4

1.5Mb/s

PDH System:

SDH Basic Concept

140/34Mbit/s 34/140Mbit/s

/

Optical

signal/34/8Mbit/s 8/34Mbit/s

8/2Mbit/s 2/8Mbit/s

2Mbit/s

m

ultiplex

mu

ltiplex

mu

ltiplex

de multiplex

de

mu

ltiplex

de m

ultiplex

optic

al

electrical

electrical

optica

l

Optical

signal

SDH Basic Concept

THE PROCESS OF ADDING / DROPPING TRIBUTARIES IN PDH

PDH System:

• Faster transmission speed and more enormous capability.

• More efficient multiplexing and de-multiplexing.

• Worldwide uniform optical Network Node Interface(NNI).

• Self-healing functions of transmission network.

• Powerful Operation, Administration&Maintenance(OAM)

SDH Basic ConceptRequirements Of Modern Transmission Network

2 、 SDH Character: Advantages ： — Uniform Rate ： 155M 、 622M 、 2.5G 、 10G ；

— Uniform Optical interface and Frame Structure:

STM-N （ N=1 、 4 、 16 、 64 ）；

— Add/Drop service only by one step;

— Powerful Network OAM&P capacity

— flexible networking ,the survivability of network is powerful ；

— forward and backward compatibility 。

Disadvantage ：

— The using percentage of the bandwidth is low

SDH Basic Concept

3 、 SDH Basic Concept

3.1 、 Hierarchy and Rate

kinds

STM-1

STM-4

STM-16

STM-64

rate （ Mb/s ） 155.520

622.080

2488.320

9953.280

63

252

1008

4032

Numbers of 2M

SDH Basic Concept

3.2 、 SDH Network Topology

. Line network

TM ADM ADM TMREG

. Tree network

TM ADM ADM TMREG

ADM

TM

SDH Basic Concept

. Ring networkADM

ADM

ADM ADM

SDH Basic Concept

. Star network

TM DXC ADM TMREG

ADM

TM

TM

ADM

TM

TM

SDH Basic Concept

. Mesh network

ADM

ADM

ADM

ADM

SDH Basic Concept

Frame Structure And SOH

SOH ： Segment overhead

AU PTR ： AU management pointer

POH ： Path overhead

9×270×N Byte

1

345

9

SOH

STM-N Payload(including POH )

Direction

9×N 261×N270×N columns

SOH

AU PTR

T=125 us


Payload

High order path layer

MSOH layer


THE LEVELS OF SDH:

Low order path layer

RSOH layer

STM-N

1 、 STM-1 SOH Bytes arrangement

9 columns

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

A U - P T R (AU management pointer)

B2 B2 B2 K1 K2

D4

D5 D6

D7 D8 D9

D10 D11 D12

S1 M1 E2

RSOH

MSOH

9

rows

Direction

T=125us


2 、 SOH byte function 1. A1 、 A2 ： initial frame position bytes;

2. J0 ： Regenerating segment tracing byte ； 3. B1 ： Bit insertion parity correction 8 bit codes (BIP-8)

.

B1 Byte

Verified byte

Verified byte

Verified byte

b1 b2 b3 b4 b5 b6 b7 b8

× × × × × × × ×

1 1 0 0 1 0 0 1

1

1

0 1 0 0 1 0 1

0 0 1 1 0 1 0


4. D1~ D3 ： RS Data communication channel ； 5. D4 ~ D12 ： MS Data communication channel ； 6. E1 、 E2 ： Order-wire bytes ； 7. F1 ： User channel ； 8. B2 ： BIP-N×24 code ； 9. K1 、 K2 ： Automatic protection switching (APS)


10. S1 ： Synchronous status byte ； b5 ~ b8 = 0010 ： G.811 Clock ， 0100 ： G.812 Clock ， 1011 ： Equipment Clock ， 1111 ： No usage 。11. M1 ： (MS-REI) byte ，


Multiplexing and Mapping

1 、 Multiplexing and mapping units

1.1 、 Container C

C is an important information structure in SDH, which mainly supports various digital flows.

There are three categories:

kinds

C-12

C-3

C-4

Signal category

2 Mb/s

34 / 45 Mb/s

140 Mb/s

Structure

9 × 4–2

9 × 84

9 × 260

Rate （ Mb/s ） 2.176

48.384

149.760


1.2 、 Virtual Container VC

VC also is an important information structure in SDH, which mainly supports the path layer connection.

There are three categories:

kinds

VC-12

VC- 3

VC- 4

Signal category

2 Mb/s

34 / 45 Mb/s

2/34/45/140 Mb/s

Structure

9 × 4–1

9 × 85

9 × 261

Rate （ Mb/s ） 2.240

48.960

150.336


VC-12 VC-3

POH

C-3 ( 34/45Mb/s )

85

POHC-12

( 2Mb/s )

4

9


C-4

( 140 Mb/s )

POH

261

9 3×TUG-3

( 2/34/45 M )

POH

261

9

VC-4 (a) VC-4 (b)

R

2

R

1

note ： TUG3 = 7 × TUG -12= 21 × TU-12 （ 63 × VC12 ） TUG3 = TU - 3 （ VC-3 ）


1.3 、 Tributary Unit TU

TU is an information structure that performs adaptation functions for the low order path layer and high order path layer 。

Kinds

TU-12

TU- 3

Including

VC12+ TU12 PTR

VC3+ TU3 PTR

Structure

9 × 4

9 × 85+3

Rate （ Mb/s ） 2.304

49.152


H1H2H3

TU PTR

VC-12 VC-39

TU-12 TU-3

4 85

9


1.4 、 Tributary unit Group (TUG)

One or more TUs with fixed locations form a TUG 。

Kinds

TUG- 3

Including

3 × TU-12

7 × TUG-2

Structure

9 × 12

9 × 86

Rate （ Mb/s ） 6.912

49.536

TUG- 2


3×TU - 12 7×TUG-2

（ 1×TU- 3）

9

TUG-2 TUG-3

R means filled bytes

12 86

9RR


1.5 、 Administration unit-4 AU- 4

AU-4 Performs adaptation functions for the high order path layer and multiplexing segment layer 。 AU-4 consists of high order VC and AU PTR 。

AU-PTR VC - 4 9

261

9


2 、 Pointer

2.1 、 Purpose

— Indicate the position of payload

—Rate adjustment 。

2.2 、 Categories

Administration unit pointer AU PTR ； Tributary unit pointer TU-3 PTR 、 TU-12 PTR


3 、 AU PTR

3.1 、 Position and Structure

9

261

AU-PTR

9

H1Y Y H2 1* 1* H3 H3 H3

Y= 1001SS11

1*=11111111

VC - 4


3.2 、 H1 、 H2 、 H3 bit arrangement

N N N N S S I D I D I D I D I D

H1 H2 H3 H3 H3

NDF 10 bit pointer Negative adjustment

byte

AU

kinds

NDF ： New data flag

SS ： AU categories ， SS=11 ： AU-4

I ： Increased bits

D ： reduced bits


3.3 、 H1 、 H2 、 H3 byte function

. To indicate the position of Payload

. To adjust the rate of VC-4

. To indicate New Data flag (NDF)


4 、 TU-3 PTR


H1H2H3 VC-3

9

85

TU-3


4.2 、 H1 、 H2 、 H3 bit arrangement


H1 H2 H3


byte

AU

kinds


SS ： AU categories ， SS=00 ： TU-3


D ： reduced bits


4.3 、 H1 、 H2 、 H3 Byte function



. New data flag (NDF)


5 、 TU-12 PTR


V1VC-12

V2 VC-12

V3 VC-12

500μs Multi-Frame

V4VC-12


5.2 、 V1 、 V2 、 V3 bit arrangement


V1 V2 V3


byte

AU

kinds


SS ： AU categories ， SS=10 ： TU-12


D ： reduced bits


5.3 、 V1 、 V2 、 V3 Byte function



. New Data flag (NDF)


6 、 High Order VC-4 / VC-3 POH


VC- 4 / VC-3

J1

B3

C2

G1

F2

H4

F3

K3

N1


6.2 、 POH Byte function

• J1 ： High order path tracing byte; • B3 ： High order path error code monitoring byte,BIP-8(code)

; • C2 ： To represent the composition of VC-3/4 structure;

G1 ： Path status byte ： REI 、 RDI;• F2 、 F3 ： User channel ;• H4 ： To indicate the position of multi-frame;• K3 ： Automatic protection switching (APS) byte ;• N1 ： Network operator byte 。


7 、 Low Order VC-12 POH

7.1 、 Position and Structure V5VC-12

J2VC-12

500μs Multi-frame

VC-12N2

K4VC-12


7.2 、 Byte function

• V5 ： Path status and signal tag byte ; b1b2 ： Path bit insertion parity correction 8 bit codes (BIP-2); b3 ： REI ; b4 ： RFI ; b5b6b7 ： signal category,Mapping mode;

b8 ： RDI;• J2 ： Low order path tracing byte ;

• N2 ： Network operator byte ;

• K4 ： Automatic protection switching (APS) byte 。


8 、 Byte Interleaving Multiplex

Adaptation of multiple low order path layer signals to high order path layer signal or multiple high order path layer signals to a multiplexing segment layer.

2

b

1 2 3 1 3 1 2 3

ca cba

TU-12 a TU-12 b TU-12 c

TUG-2

4 4 4


9 、 Mapping

9.1 、 Mapping

The process of putting various tributary signals into related VC is called mapping 。 For example:Putting 2Mb/s signal into VC-12 ； Putting 34 （ or45 ） Mb/s signal into VC-3 ； Putting 140Mb/s signal into VC-4 。


10 The mapping and multiplexing Structure

C 4

Adjustment

AUG

TUG-2

VC-3 C-3

TU-12 VC-12 C-12

（ 140M ）

（ 34M / 45M）

（ 2M ）

Pointer processMapping

Multiplexing

×N

×7

×3

×3

TUG3

STM-N AU-4 VC-4

TU - 3×1

×1C-4


STM-N

× N × 1C-12VC-12VC-4 TUG-2AUG-4 AU-4 TU-12 2Mb/s

bit rate adjustment

LO POH

TU PTR

AU PTR× ３ multiplex

×7multiplex

HO POH

× ３ multiplex

N×multiplex

TUG-3

Multiplexing and MappingTHE JOURNEY OF 2Mbit/s IN STM-N

Synchronous Multiplexing System

1 Synchronous Multiplexing Equipment Categories

. Terminal Multiplexer (TM)

In the end station of chain network, TM is used to multiplex/de-multiplex the PDH/SDH tributary signals to/from line SDH signal.

PDH/SDH tributary signal

OAM

Line signal

STM-N

TM


. Add/Drop Multiplexer (ADM)

ADM is placed in the middle station of the network ， which performs to add/drop service function 。

STM-NSTM-N

West signal

PDH/SDH tributary signal

OAM

East signal

ADM


. Regenerator (REG)

REG is placed in the middle station of the network ， which mainly used to amplify optical power so as to extend the optical transmission distance ， but it can not add/drop service.

OAM

East signalWest signal

STM-NSTM-N

REG


2 、 Characters

1 、 One step Multiplexing

Add/Drop tributary signal （ Drop 2M from 2.5G ）。

2 、 Powerful Cross-connect Capacity

Realize:line to line, line to tributary and tributary to tributary cross-connection.

3 、 Powerful OAM Capacity

4 、 Flexible networking capacity

5 、 Powerful network survivability


3 、 Cross performance indices

. Cross hierarchy

High order cross ： VC-4 level cross connection.

Low order cross ： VC-12 level cross connection 。 Which can guarantee to drop 2M service from high rate service directly 。


、 Cross capacity

Cross capacity is generally written as n × n VC-4 。 For example:2.5G ADM provide powerful cross capacity 。 high order cross capacity ： 96 × 96 VC-4.


. Cross category

Provide the following categories at least ：Uni-direction ： The crossed port only be used as output 。Bi-direction ： Every port can be used as both the input signal port and the output signal port 。Broadcast ： Every input signal can connect with more ports。


4 、 System Structure

Timing Communication Unit

OW

PDH & SDH tributary interface

LI LI

cross matrix


4.1 、 Line interface

Line signal STM-N O-E conversion ； Process AU_PTR ； produce/end SOH 。

4.2 、 Cross matrix

Complete the cross-connection function of high –speed signals based on VC_4;

Add/Drop service to/from high speed signals.


4.3 、 Tributary interface

Add/Drop service at the station 。 Service Categories:2M 、 34M 、 45M 、 140M 、 155M etc.

4.4 、 Timing unit

Inside ： Provide timing signal to internal units

Outside ： Tracing external timing signal ； Drop timing signal from Line/Tributary signal ； Holdover/oscillation 。


4.5 、 Communication and control unit

Collect data from all units ； Present to NMS through DCC path ， On the contrary, receive commands from NMS and implement them.

4.6 、 Order Wire unit

Provide order wire for contact 。


SDH Self-healing Network

1.1 Self-healing Network

Self-healing network can automatically recover the carrie

d services from a failure fault in a very short period of time.

1.2 Types of self-healing network

1 Line protection switching(less than 50 ms)

2 Self-healing ring network


1.3 Categories of self-healing ring network 1 Path protection switching ring

2 Multiplex segment protection switching ring

Unidirectional MSPS

Bi-directional MSPS

SDH self-healing network


Line protection switching Self-healing ring network

Path protection switching ring

Multiplex segment protection switching ring

Unidirectional MSPS Bi-directional MSPS

Types of SDH self-healing network:


Normal condition

1.4 Two-fiber Unidirectional Path Protection Ring


Principle ： send together and receive first

S:service optical ，P:protection optical 。Normal ：From A to C ：S ： A --- B --- C ， P ： A --- D --- C 。 similar ， From C to A ： S ： C --- D --- A ； P ： C --- B --- A 。


Fault condition

Two-fiber unidirectional path protection switching ring


Fault ：The cable between B and C is cut off

AC service ： the signal come from A is lost ，So switching to the P optical fiber.

Receive signal via ： A --- D --- C

CA service is in the original way.


1.5 Two-fiber MS-Shared Protection Ring

Normal condition


Normal ：AC signals are transmitted along S1/P2 optical fiber in clock direction while CA signals along S2/P1 in anticlockwise direction.

From A to C ：S ： A --- B --- C

From C to A ：S ： C --- B --- A

P1 and P2 can transmitted additional service.


Fault condition

SDH self-healing networkTwo-fiber MS-Shared Protection Ring

Fault:

The cable between B and C is cut off

AC service ： the signal come from A is lost ，So switching to the P optical fiber.

Receive signal via ： A --- D --- C

CA service is in the original way.

At B node: Switching to the anticlockwise direction ： A---B--- A --- D --- C 。At C node ： Switching to the clockwise direction ： C --- D --- A 。


Network Synchronization

1 、 Multiple Clock sources

. External clock source

. Drop clock source from STM-N interface

. Internal clock source

A). Holdover mode

Utilize pre-24hours memory information to stimulate synchronous status ； precision index ： 0.37ppm 。B). oscillation

precision index ： 4.6ppm 。

Network Synchronization

Network Synchronization1 Network synchronization

Network synchronization is one important part in the network. Which can ensure the transmitting end and the receiving end working in the synchronous status.

2 SSM function

SSM is transferred by the fifth to the eighth bits of S1 byte.

b1 b2 b3 b4 b5 b6 b7 b8

SSMThese four bits have 16 different kinds of codes

representing 16 different synchronization quality grades

Network Synchronization3 Selection of clock source

The NE first selects the clock of highest quality grade.

The NE selects the clock source which passes the least numbers of NE.

Thanks!

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SDH Principle