03-SDH Principle-20080528-A

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

SDH Principle

Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page1

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 transmission

Headache for network planners

More equipment to achieve this functionality

More equipment More floor space

More 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 ATM SDH Ethernet

Pack

SDH Network Processing

PDH ATM SDH Ethernet

Transmit Receive

Container

STM-N STM-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

RSOH 1

2

3

4

5 6 7

8

9

270 Columns

9 rows

Three parts:

SOH

AU-Pointer

Information

Payload


SDH Frame Structure

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-PTR Payload

RSOH

270 Columns

HP

OH

1

package

package

low rate signal

LPOH, TU-PTR

LPOH, TU-PTR

9 rows

Data

package


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 ~ #9

2. MSOH: rows #5 ~ #9,

columns #1 ~ #9

1

2

3

5

6

7

8

9

MSOH

AU-PTR Information

Payload

RSOH

Section Overhead


SDH Frame Structure

9

MSOH

AU-PTR Information

Payload

RSOH

270 Columns

9 rows 4

Function:

Indicates the first byte of VC4

Location:

row #4, columns #1 ~ #9

J

1

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-3 TUG-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-4-4c VC-4-4c AU-4-4c 1

C-4-16c VC-4-16c AU-4-16c 1

C-4-64c VC-4-64c AU-4-64c 1

SDH Multiplexing Structure


From 140Mb/s to STM-N

140M Rate

adaptation Add HPOH

C4

9

1 260

125 s

1

Next

Mapping

VC4

1

9

125s 1 261

H

P

O

H



Add

AU-PTR Add

SOH

Alignin

g

AU-PTR AU-4

10 270

X1

AUG-1

Multiplexing

AUG-N

1 270

RSOH

MSOH

Info

Payload AU-PTR

9

STM-1

Add

SOH

One STM-1 frame can load

only one 140Mbit/s Signal

1 270N

RSOH

MSOH

Info

Payload AU-PTR

9

STM-N



34M Rate

Adaptation Add LPOH

C3

1 84

9

125s

1 1

9

VC3

L

P

O

H

125s 1 85

Next

Mapping



1st

align

Fill

gap 3

8

6

TU-3

1

H1

H2

H3

1

9

1 86

1

9

H1

H2

H3

R

TUG-3

Multiplexing

H

P

O

H

R

R

VC-4

9

1

1 261 3

Same

procedure

as 140M

Alignin

g


From 2Mb/s to STM-N

2M Next

page

125s

1 4

C12

1

9

4 LPOH

VC12

1

1

9

Rate

Adaptation Add

LPOH Add

TU-PTR

Aligning

TU12

1 4

1

9

TU-PTR Mapping


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

Multiplexing Same

procedure

as 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

HP

OH

: V

C-3

/4

J1

B3

C2

G1

F2

H4

F3

K3

N1

RSO

H

MSO

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

V5 J2 N2 K4


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 Bytes Frame

Next

process

Find

A1,A2

OOF

LOF

N

Y

AIS

over 3ms

over 625s (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 NE NE

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 channel

E1-RS, E2-MS

E1 and E2

NE NE NE NE


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 00110011

A2 11001100

A3 10101010

A4 00001111

B 01011010

BIP-8

B1 = B

STM-N B1

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

WTR P

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 alarm

Generate

MS-AIS

Start

Detect

K2 (b6-

b8)

Return

MS-RDI

Generate

MS-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

0000 Quality 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

G1

F2

H4

F3

K3

N1

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

1

2

3

4

5

6

7

8

9

R S O H

M S O H

A U P T R


J1 Byte

Next

process

Detect J1

Match

HP-TIM

Y N

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

Y N Correct

HP-BBE

Path bit parity

Even parity code

Used to detect bit errors

Mechanism is same as B1 and B2


C2 Byte

Detect C2

00H

HP-UNEQ Match

HP-SLM Next

process

Insert AIS

downward

N Y

N Y

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-12 VC-12 VC-12 VC-12

K4 N2 J2 V5 1

9

1 4

500s 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 J1 TU-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

125s

250s

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

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

Negative

justificatio

n

Positive

justification

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

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

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

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


TU-PTR

VC3

H1

H2

H3

TU 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 500s


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 you www.huawei.com

Documents

03-SDH Principle-20080528-A