Training PPT,SDH Principle,20040423

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Transcript of Training PPT,SDH Principle,20040423

Internal Use Only

Basic Principles of SDHPre-sales Comm. And Tech. Support, OTPD Pang Lipeng

Outline Overview to SDH

Internal Use Only

Rate and frame structureMultiplexing structure and

proceduresSDH network protection

SDH network synchronization

Add/drop 2Mbit/s signals Internal Use Onlyin PDH and SDH systems O / EE / O Demultiplexing Multiplexing Demultiplexing


2Mbit/selectrical signals155Mb/sOptical interface

2Mbit/selectrical signals




155Mb/sOptical interface

SDH feature-- plentiful overhead bytes

Internal Use Only

1. SDH system is an intelligent equipment with powerful self-healing function. SDH NMS and dynamic configuration with intelligent check contribute to easy self-healing of SDH network. When a fault occurs to the equipment or system, the services can be recovered rapidly, greatly improving network reliability and lowering maintenance cost. 2. SDH system has good network management function. The overhead bytes (1/10 of the total capacity) in the SDH frame may meet the present requirements in the alarm, performance supervision, network configuration, switching and orderwire, and can be extended further to satisfy the future requirements in the supervision and NM. SDH advantages: Synchronous multiplexing, standard optical interface and powerful NM.

Internal Use Only

SDH shortcomings: 1. The frequency band utilization rate of SDH is lower than that of PDH. 2. The pointer adjustment makes the equipment and interfaces more complex. 3. The software control function easily causes major faults.

Outline Overview to SDH

Internal Use Only

Rate and frame structureMultiplexing structure and

proceduresSDH network protection

SDH network synchronization

SDH rates

Internal Use Only


SDH level

SONET levelOC-3/STS3(1440CH) OC-12/STS-12(8046CH)

Standard rate 155.520Mbit/s 622.080Mbit/s

155M STM-1(1920CH) 622M STM-4 2.5G 10G STM-16 STM-64

OC-48/STS-48(32356CH) 2488.320Mbit/s OC-192/STS-192 9953.280Mbit/s 39813.120Mbit/s

40G STM--256


STM- Synchronous transfer mode

STM-1 frame structure8000 frames/s

Internal Use Only

capacity = 9 270 bytes

SOH 9 rowsAU-PTR


SOHsection overhead



9 columns

270 columns (byte)

Frame structureSTM-N frame structure9270N bytes 125s1

Internal Use Only



AU pointer

SDH payload with POH

Transmission direction

SOHFrame period, 9 frame frequency block and rate


261 N

Byte interleave synchronous Internal Use Only multiplexingByte interleaver multiplexert

STM-1 Signal A STM-1 Signal B STM-1 Signal C


STM-4 signal (4STM-1)

STM-1 Signal D

Internal Use Only


Information payloads --They contain various information blocks and some POH bytes used for channel performance supervision, management and control. Section overheads--They are the additional bytes ensuring the normal and flexible transmission of information payload. They provides the frame synchronization and network OAP bytes. SOH consists of RSOH and MSOH. RSOH terminates in the regenerator, and MSOH transparently goes through the regenerator and is assembled/dissembled in AUG. AU-PTR --It indicates the accurate position of the first byte of information payload in STM-N frame, and employs the pointer adjustment technique to resolve the clock deviation of network node so that the information payload can be detached properly at the receiving end of SDH system.



Internal Use Only SDH network segment model

MSTributary signalsRS


Tributary signals




VC multiplexing


VC demultiplexing

Path, MS and RS

SOH bytesSTM-1 SOH bytes9 columnsA1 B1 D1 A1 B2 A1 A2 E1 D2 A2 A2 J0 F1 D3 K2 D6 D9 * *

Internal Use Only


9 rowsB2 D4 D7 D10 S1

AU PRT B2 K1 D5 D8



D12M1 E2

Description for SOH byte Internal Use Only

framing bytes: A1, A2 bytes identifies the initial location of the

frame. The byte code pattern are defined as A1: 11110110F6H A2: 0010100028H (transparent transmission)RS

trace byte: J0

It repeatedly transmits the section AP identity to assure the receiver of the connection with the receiver assigned. The section AP identity adopts the format in section 3 of ITU-T G.831, that is, use a 16-byte frame to transmit the section AP identity. byte number 8bit value 1 1 C1 C2 C3 C4 C5 C6 C7 2 0 X X X X X X X 3 0 X X X X X X X . 16 0 X X X X X X X

note: the first byte is the initial location identity of the frame. C1-C7 is the calculation result of CRC-7 in the previous frame. The other 15 bytes transmit the section AP identity.

Internal Use Only

Data Communication Channel (DCC): D1D12 SOH DCC is the transmission link of SDH management network (SMN). D1~D3 byte transmits OAM information between RS terminals. D4~D12 byte transmits OAM information between MS terminals. One purpose of SDH network management control is to implement the fast distributed control. The best route table calculated by NMS can be delivered quickly to NE via DCC at any time. DCC is the SDH physical channel and has the protocol stack Qecc.

Orderwire channel: E1 and E2 E1 and E2 offers the orderwire voice channel. E1 is used for the RS orderwire and E2 for the orderwire between terminals.User channel: F1 It is for the network provider. It is used for the special maintenance of system operator, e.g., providing temporary 64kb/s data/voice channel.

Internal Use Only

B1: BIP-8 B1 supervises the MS bit error in BIP-8 method. After all the bytes scrambled in the previous frame of STM-N make the BIP-8 check, the result is in the B1 byte before unscrambled in the present frame. The bit error supervision is one of SDH characteristics. It can automatically supervise the MS bit error in a simple way. But this mode can not check out the even number of bit errors in one supervise code group. (This case seldom occurs, but a certain error exists.B2: BIP-N24 It makes the online of supervision of the MS bit error in the BIP-N24 method. The BIP-N24 value of all bytes in the previous STM-N frame is in B2 before scrambled in the present frame. The first three lines of SOH is not for check.

Internal Use Only APS channel: K1 and K2b1-b5 The two bytes are used for APS instruction. (K1 indicates the switching type and channel No., and K2 indicates the channel No. switched to the protection channel.) MS-RDI byte: K2 (b6-b8) MS-RDI sends back an instruction signal to the transmitting end, indicating that the receiving end finds an incoming fault or is receiving MS-AIS. After unscrambled, K2 (b6-b8) forms 110, that is, MS-RDI. Synchronization state: S1b5-b8 S1 (b5-b8) transmits the synchronization state information, that is, the synchronization state of the upstream station is transmitted to the downstream station via S1 (b5-b8). S1 (b5-b8) b5-b8) Clock level 0000 Unknown quality 0010 G.811 reference clock 0100 G.812 exchange slave clock 1000 G.812 local slave clock 1011 SETS 1111 Not for clock synchronization

Internal Use OnlyMS-REI:

M1 M1 is used for MS-REI. It sends the quantity of the bit errors checked out by B2. related to transmission media: One-fiber unidirection, one-fiber bidirection, etc. Backup bytes -Free byte (for future use in the international standard) (Note: The bytes with * will not be scrambled.Bytes STM-N(N>1)

SOH It is formed in the byte interleaving mode. The SOH in the first STM-1 is remained, but the SOH in other N-1 STM-1 is remained only with byte A1, A2 and B2.

STM-4 SOH bytes36 byte

Internal Use Only

9 rows



STM-16 SOH bytes144 bytes A1 A1 A1 B1 D1 B2 B2 B2 A1 A2 A2 A2 E1 D2 K1 D5 D8 D11 AU PRT B2 D4 D7 D10 S1 FEC

Internal Use Only


J0/C1 Z0/C1 Z0/C1

F1 D3 K2 D6 D9 D12 E2 M1


9 rows

STM-64 SOH bytes576 bytes A1 A1 A1 B1 D1 B2 A1 A2 A2 A2 E1 D2 K1 D5 D8 D11 AU PRT K2 D6 D9 D12 E2 M1 A1

Internal Use Only

J0/C1 Z0/C1 Z0/C1

F1 D3


9 rows B2 B2 B2D4 D7 D10 S1


FEC (Forward Error Correction) Internal Use OnlySome bytes in SOH of STM-16 ~ STM-256 are used for FEC. FEC means that the signals are coded in a certain format before transmission, then they are decoded with a specific algorithm at the receiver in order to find out the bit errors and correct them.

ITU-I G.975, issued in 1996, employs FEC as a part of the cable communication standards. The new draft, passed in April, 2000, is added with FEC as an option in the 10Gbit/s system.

Outline Overview to SDH

Internal Use Only

Rate and frame structureMultiplexing structure and

proceduresSDH network protection

SDH network synchronization

Internal Use Only

Multiplexing structure and proceduresNSTM-N AUG

1AU-4 VC-4



3AU-3 VC-3 TUG-3


VC-3 C-3 VC-2 VC-12 VC-11 C-2 C-12 C-11

45Mb/s 34Mb/s6.3Mb/s 2Mb/s 1.5Mb/s

1 TUG-2 TU-2 3TU-12

4 4TU-11



Mapping Positioning Multiplexing

Multiplexing structure in G.707

Mapping structure in China Internal Use Only

Pointer processingPositioning Multiplexing