Ota000004 Sdh Principle Issue 2.30

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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

SDH Principle

Page2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

Contents

1. SDH Overview

2. Frame Structure & Multiplexing Methods

3. Overheads & Pointers


Emergence of SDH

What is SDH?

Synchronous Digital Hierarchy

It defines a standard frame structure, a

specific multiplexing method, and so on.

Why did SDH emerge? Need for a system to process increasing amounts of information.

New standard that allows interconnecting equipment of different suppliers.


Advantages of SDH

Interfaces

PDH electrical interfaces

Only 3 regional standards:

European (2.048 Mb/s),

Japanese, North American

(1.544 Mb/s)

PDH optical interfaces

No standards,

manufacturers develop at

their will.

SDH electrical interfaces

Universal standards

SDH optical interfaces

Can be connected to

different vendors’

optical transmission

equipments.


140 Mb/s

34 Mb/s 34 Mb/s

8 Mb/s 8 Mb/s

2 Mb/s

140 Mb/s

Not suitable for huge-volume transmissionHeadache for network planners

More equipment to achieve this functionalityMore equipment More floor spaceMore power More costs

Demultiplexers Multiplexers

Multiplexing methods: Level by level

Disadvantages of PDH


Advantages of SDH

Lower rate SDH to higher rate SDH (STM-1 STM-4 STM-16 STM-64)

4:1

STM-1

A

STM-1

B

STM-1

C

STM-1

D

A

B

D

C

B

A

D

C

B

A

…

STM-4

One Byte from STM-1 B

--- Synchronous multiplexing method and flexible mapping structure

--- Multistage pointer to align PDH loads in SDH frame, thus, dynamic drop-and-insert capabilities

What about PDH?

Multiplexing methods: byte interleaved


Advantages of SDH

OAM function

PDH

In the frame structure

of PDH signals, there

are few overhead

bytes used for OAM.

Weak OAM function

SDH

Abundant overheads

bytes for OAM

Remote & Centralized

Management

Fast circuit

provisioning from

centralized point


Advantages of SDH

Processing

PDH ATMSDH Ethernet

Pack

SDH Network

Processing

PDH ATMSDH Ethernet

Transmit Receive

Container

STM-NSTM-N

Container

Service Signal Flow Model

Unpack

Compatibility


Comparison between SDH and PDH Low bandwidth utilization ratio

In PDH, E4 signal (140Mbits/s) can contain 64 E1 signals. In SDH, STM-1 (155 Mbits/s) can only carry 63 E1 signals.

Complex mechanism of pointer justification Influence of excessive use of software on system security


Contents

1. SDH Overview




SDH Frame Structure

From ITU-T G.707:

1. One frame lasts for 125 microseconds (8000 frames/s)

2. Rectangular block structure 9 rows and 270 columns (Basic frame: STM-1)

3. Each unit is one byte (8 bits)

4. Transmission mode: Byte by byte, row by row, from left to right, from top to bottom

Bit rate of STM-1= 9*270*8*8000

1 2

3 4

5 6

7 8

9

270 Columns

9 rows

Frame = 125 us


SDH Frame Structure

Frame = 125 us

9

MSOH

AU-PTR Information

Payload

RSOH1 2

3 4

5 6

7 8

9

270 Columns

9 rows

Three parts:

SOH

AU-Pointer

Information

Payload


SDH Frame StructureInformation Payload√ Also known as Virtual Container level 4 (VC-4)√ Used to transport low speed tributary signals√ Contains low rate signals and Path Overhead (POH)√ Location: rows #1 ~ #9, columns #10 ~ #270

Information Payload√ Also known as Virtual Container level 4 (VC-4)√ Used to transport low speed tributary signals√ Contains low rate signals and Path Overhead (POH)√ Location: rows #1 ~ #9, columns #10 ~ #270

9

MSOH

AU-PTRPayload

RSOH

270 Columns

HPO

H

1

package

package

low rate signal

LPOH, TU-PTR

LPOH, TU-PTR

9 rows

Data packag

e


SDH Frame Structure

Functions: Fulfills the section layer OAM

9

270 Columns

9 rows

Types of Section Overhead

1. RSOH monitors the regenerator section

2. MSOH monitors the multiplexing section

Location:1. RSOH: rows #1 ~ #3, columns #1 ~ #92. MSOH: rows #5 ~ #9, columns #1 ~ #9

1 2

3 5

6 7

8

9

MSOH

AU-PTR Information

Payload

RSOH

Section OverheadSection Overhead


SDH Frame Structure

9

MSOH

AU-PTR Information

Payload

RSOH

270 Columns

9 rows4

Function: Indicates the first byte of VC4

Location: row #4, columns #1 ~ #9

J1

AU-PTR AU-PTR


SDH Multiplexing Features

SDH Multiplexing includes:

Low to high rate SDH signals (STM-1 STM-N)

PDH to SDH signals (2M, 34M & 140M STM-N)

Other hierarchy signals to SDH Signals (IP STM-N)

Some terms and definitions:

Mapping

Aligning

Multiplexing

Go to glossary


AU-4

TU-3TUG-3 VC-3 C-3

VC-4 C-4

TU-12 VC-12 C-12

TUG-2

×3

×1

×7

×3

E4 signal

E3 signal

E1 signal

Multiplexing

Mapping

Aligning

STM-1 AUG-1×1

×1

AUG-4

AUG-16

AUG-64

STM-4

STM-16

STM-64

×1

×1

×1

×4

×4

×4

Go to glossary

C-4-4cVC-4-4cAU-4-4c×1

C-4-16cVC-4-16c

AU-4-16c×1

C-4-64cVC-4-64c

AU-4-64c×1

SDH Multiplexing Structure


From 140Mb/s to STM-N

140MRate

adaptationAdd HPOH

C4

9

1 260125 μs

1

Next

Mapping

VC4

1

9

125μs1 261

HPOH



AddAU-PTR

AddSOH

Aligning

AU-PTR AU-4

10 270

X1

AUG-1

Multiplexing

AUG-N

1 270

RSOH

MSOH

InfoPayloadAU-PTR

9

STM-1

Add

SOH

One STM-1 frame can load only one 140Mbit/s Signal

1 270N

RSOH

MSOH

InfoPayloadAU-PTR

9

STM-N



34M Rate Adaptation

Add LPOH

C3

1 84

9

125μs

1 1

9

VC3

LPOH

125μs1 85

Next

Mapping



1st align

Fillgap

×3

86

TU-3

1

H1H2H3

1

9

1 86

1

9

H1H2H3

R

TUG-3

Multiplexing

HPOH

R

R

VC-4

9

11 26

13

Same procedureas 140M

Aligning


From 2Mb/s to STM-N

2M Nextpage

125μs

1 4

C12

1

9

4LPOH

VC12

1

1

9

Rate Adaptation

Add LPOH

Add TU-PTR

Aligning

TU12

1 4

1

9

TU-PTRMapping


From 2Mb/s to STM-N

X 3

1 12

TUG-2

1

9

X 7

Multiplexing

R R

TUG-3

1 86

1

9

MultiplexingSame procedureas 34M


Questions

What are the main parts of SDH Frame structure?

What is the transmission rate of STM-4? How to calculate it ?


Contents

1. SDH Overview




Overheads

Overheads

Section Overhead

(SOH)

Path Overhead

(POH)

Regenerator Section

Overhead (RSOH)

Multiplex Section

Overhead (MSOH)

High Order Path Overhead

(HPOH)

Low Order Path Overhead

(LPOH)


Overheads

A1 A1 A1 A2 A2 A2 J0 X X

B1 ● ● E1 ● F1 X X

D1 ● ● D2 ● D3

AU-PTR

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 M1 E2

HPO

H:

VC

-3/4

J1

B3

C2

G1

F2

H

4

F3

K3

N

1

RSO

HM

SO

H

1 2 3 4 5 6 7 8 9 10

1

2

3

4

5

6

7

8

9

● Media dependent bytes (Radio-link, Satellite)X Reserved for National use Huawei propriety bytes LPOH: VC-11/12

V

5J2

N

2

K

4


A1 and A2 Bytes

Framing Bytes

Indicate the beginning of the STM-N frame

Bytes are unscrambled

A1 = f6H (11110110), A2 = 28H (00101000)

STM-N: (3XN) A1 bytes, (3XN) A2 bytes

STM-N STM-N STM-N STM-N STM-N STM-N

Finding frame head


A1 and A2 BytesFrame

Nextprocess

FindA1,A2

OOF

LOF

N

Y

AIS

over 3ms

over 625μs (5 frames)


D1 ~ D12 Bytes

Data Communications Channel (DCC) Bytes

RS-DCC – D1 ~ D3 – 192 Kbit/s (3x64 Kbit/s)

MS-DCC – D4 ~ D12 – 576 Kbit/s (9x64 Kbit/s)

TMN

DCC channel

NE NE NENE

OAM Information: Operation, Administration and maintenance


E1 and E2 Bytes

Orderwire Bytes

E1 – RS Orderwire Byte Used between regenerators

E2 – MS Orderwire Byte Used between multiplexers

Digital telephone channelE1-RS, E2-MS

E1 and E2

NE NE NENE


B1 Byte

Bit interleaved Parity Code (BIP-8) Byte

A parity code (even parity)

Used to check the transmission errors over the RS

B1 BBE is represented by RS-BBE (performance event)

Tx

2#STM-N

Rx

1#STM-N Calculate B

1#STM-N

2#STM-N

Calculate B’

A1 00110011A2 11001100A3 10101010A4 00001111

B 01011010

BIP-8

B1 = B

STM-NB1

B

Compare B’ & B RS-BBE


B2 Byte

Bit interleaved Parity Code (MS BIP-24) Byte

BIP-24 is used to check the bit errors over the MS

B2 BBE is represented by MS-BBE (performance event)

The working mechanism of B2 is same as B1


M1 Byte Multiplexing Section Remote Error Indication Byte

A return message from Rx to Tx ,when Rx find B2 bit errors Value is the same as the count of BIP-24xN (B2) bit errors Tx generate corresponding performance event MS-FEBBE

Tx Rx

Traffic

Generate

MS-FEBBE

MS-REI

Find B2 bit errors

Generate MS-BBE

Return M1


K1 and K2 (b1-b5) Bytes

Automatic Protection Switching

(APS) bytes

Transmitting APS protocol Used for network multiplexing protection switch function

P

WTR

WTRP

I

I

I I

P

S

S P


K2 (b6 ~ b8) Byte

Rx detects K2 (b6-b8) =

"111“

Generate MS-AIS alarm

Rx detects K2 (b6-b8) =

"110"

Generate MS-RDI alarmGenerateMS-AIS

Start

DetectK2 (b6-

b8)

Return MS-RDI

GenerateMS-RDI

111

110


S1 Byte

Synchronization Status Message Byte (SSB): S1

b1 ~ b4 Value indicates the external clock ID (Extended SSM)

b5 ~ b8 Value indicates the sync. Level (Standard SSM)

bits 5 ~ 8 Description

0000Quality unknown (existing sync. Network)

0010 G.811 PRC

0100 SSU-A (G.812 transit)

1000 SSU-B (G.812 local)

1011 G.813 (Sync. Equipment Timing Clock)

1111 Do not use for sync (DNU).


Path Overheads

J1

B3

C2

G

1

F2

H

4

F3

K3

N

1

VC-n Path Trace Byte

Path BIP-8

Path Signal Label

Path Status

Path User Channel

TU Multiframe Indication

Path User Channel

AP Switching

Network Operator

Higher Order Path Overhead

1 2 3 4 5 6 7 8 9 10

123456789

R S O H

M S O H

A U – P T R


J1 Byte

Next process

Detect J1

Match

HP-TIM

YN

Path trace byte

The first byte of VC-4

User-programmable

(HUAWEI SBS)

The received J1 should

match the expected J1


B3 Byte

Next process

Verify B3

YNCorrect

HP-BBE

Path bit parity

Even parity code

Used to detect bit errors

Mechanism is same as B1 and B2


C2 ByteDetect C2

00H

HP-UNEQMatch

HP-SLM

Next proces

s

Insert AIS downward

N Y

NY

Signal label byte

The received C2 should

match with the expected

C2

Specifies the mapping

type in the VC-n

00 H Unequipped

02 H TUG structure

13 H ATM mapping


VC-12VC-12VC-12VC-12

K4N2J2V51

9

1 4

500μs VC-12 multi-frame

Low Order Path Overhead V5

Indicated by TU-PTR

Error checking, Signal Label

and Path Status of VC-12

b1 - b2 Error Performance

Monitoring (BIP-2)

b3 Return Error detected

in VC-12 (LP-REI)

b8 Return alarm detected

in VC-12 (LP-RDI)

Path Overheads


Pointers

Pointers

Administrative Unit Pointer

(AU-PTR)

Tributary Unit

Pointer (TU-PTR)

Bytes indicated

AU-PTR VC-4 J1TU-PTR VC-3 J1

VC-12 V5


AU-PTR

RSOH

MSOH

MSOH

RSOH

H1YYH2FF H3H3H3

H1YYH2FFH3H3H3

0 --- 1--- --- --- --- --- --- --- --- --- --- 86

696 --- 697 --- --- --- --- --- --- --- --- 782

1 9 270

1

4

9

1

4

9

125μs

250μs

522 --- 523 --- --- --- --- --- --- --- --- 608

435 --- 436 --- --- --- --- --- --- --- --- 521

Negative justification

Positive justification

0 --- 1 --- --- --- --- --- --- --- --- --- --- 86

435 --- 436 --- --- --- --- --- --- --- --- 521

87 --- 88 --- --- --- --- --- --- --- --- --- 173

87 --- 88 --- --- --- --- --- --- --- --- --- 173


TU-PTR

VC3

H1

H2

H3TU POINTERS

VC-

12

VC-

12

VC-

12

VC-

12

V

1

V

2

V

3

V

4

1 4

1

9

TU POINTERS

TU Multi-frame 500μs


Questions

Which byte is used to report the MS-AIS and MS-RDI?

What is the mechanism for R-LOF generation?

Which byte implements the RS (MS/HP) error monitoring?


Summary

SDH Overview

Frame Structure & Multiplexing Methods

Overheads & Pointers

Thank youwww.huawei.com

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Ota000004 Sdh Principle Issue 2.30

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