SDH Principle. Copyright 2012 Huawei Technologies Co., Ltd. All rights reserved.

Transcription

1 SDH Principle

2 Objectives Upon completion of this course, you will be able to: Understand the basic of SDH multiplexing standard Know the features, applications and advantages of SDH based equipment Page1

3 Contents 1. SDH Overview 2. Frame Structure & Multiplexing Methods 3. Overheads & Pointers Page2

4 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 a system to process increasing amounts of information Need a new standard that allows interconnecting equipment of different suppliers Page3

5 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 SDH electrical interfaces Universal standards SDH optical interfaces Can be connected to different vendors optical transmission equipments develop at their will Page4

6 Disadvantages of PDH Multiplexing methods: Level by level 140 Mb/s 140 Mb/s 34 Mb/s 34 Mb/s 8 Mb/s 8 Mb/s Demultiplexers Multiplexers Not suitable for huge-volume transmission Headache for network planners 2 Mb/s More equipment to achieve this functionality More equipment More floor space More power More costs Page5

7 Advantages of SDH Multiplexing methods: byte interleaved STM-1 A A A Lower rate SDH to higher rate SDH (STM-1 STM-4 STM-16 STM-64) One Byte from STM-1 B STM-1 B B B B 4:1 STM-4 STM-1 C STM-1 D C C D D What about PDH? --- Synchronous multiplexing method and flexible mapping structure --- Multistage pointer to align PDH loads in SDH frame, thus, dynamic drop-and-insert capabilities Page6

8 Advantages of SDH OAM function PDH SDH In the frame structure of Abundant overheads bytes PDH signals, there are few for OAM overhead bytes used for OAM. Remote & Centralized Management Weak OAM function Fast circuit provisioning from centralized point Page7

9 Advantages of SDH Compatibility STM-N Transmit Receive STM-N Processing SDH Network Processing Pack Container Container Unpack PDH SDH ATM Ethernet PDH SDH ATM Ethernet Service Signal Flow Model Page8

10 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 Page

11 Contents 1. SDH Overview 2. Frame Structure & Multiplexing Methods 3. Overheads & Pointers Page10

12 SDH Frame Structure From ITU-T G.707: 1. One frame lasts for 125 microseconds (8000 frames/s) 2. Rectangular block structure 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 Frame = 125 us rows Bit rate of STM-1= *270*8* Columns Page11

13 SDH Frame Structure (Cont.) Three parts: Frame = 125 us SOH AU-Pointer Information Payload RSOH AU-PTR MSOH Information Payload rows 270 Columns Page12

14 SDH Frame Structure (Cont.) 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 ~ #, columns #10 ~ #270 LPOH, TU-PTR rows RSOH AU-PTR HPOH Payload package low rate signal MSOH package Columns Data package LPOH, TU-PTR Page13

15 SDH Frame Structure (Cont.) Section Overhead Functions: Fulfills the section layer OAM RSOH AU-PTR MSOH Information Payload 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 ~ # 2. MSOH: rows #5 ~ #, columns #1 ~ # 270 Columns Page14

16 SDH Frame Structure (Cont.) AU-PTR Function: Indicates the first byte of VC4 Location: row #4, columns #1 ~ # 4 RSOH AU-PTR MSOH Information Payload rows J1 270 Columns Page15

17 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 Page16

18 SDH Multiplexing Structure 1 STM-64 1 STM-16 1 STM-4 AUG-64 4 AUG-16 4 AUG AU-4-64c AU-4-16c AU-4-4c VC-4-64c VC-4-16c VC-4-4c C-4-64c C-4-16c C-4-4c STM AUG-1 1 AU-4 VC-4 C-4 E4 signal 3 Mapping Aligning Multiplexing TUG-3 1 TU-3 VC-3 C-3 7 TUG-2 E3 signal Go to glossary 3 TU-12 VC-12 C-12 E1 signal Page17

19 From 140Mb/s to STM-N C4 VC M Rate adaptation μs Add HPOH Mapping H P O H μs Next Page18

20 From 140Mb/s to STM-N AUG-1 1 STM Add AU-PTR AU-PTR AU-4 X1 Add SOH RSOH AU-PTR MSOH Info Payload Aligning Multiplexing AUG-N 1 STM-N 270N One STM-1 frame can load only one 140Mbit/s Signal Add SOH RSOH AU-PTR MSOH Info Payload Page1

21 From 34Mb/s to STM-N C3 VC M Rate Adaptation μs Add LPOH Mapping L P O H μs Next Page20

22 From 34Mb/s to STM-N TU-3 TUG-3 VC-4 1st align 1 H1 H2 H Fill gap H1 H2 H3 R H P O H R R Aligning Multiplexing Same procedure as 140M Page21

23 From 2Mb/s to STM-N C12 VC12 TU LPOH 1 LPOH 1 2M Rate Adaptation Add LPOH Add TU-PTR Next page TU-PTR 125μs Mapping Aligning Page22

24 From 2Mb/s to STM-N TUG-2 TUG X 3 X 7 R R Multiplexing Multiplexing Same procedure as 34M Page23

25 Questions What are the main parts of SDH Frame structure? What is the transmission rate of STM-4? How to calculate it? Page24

26 Contents 1. SDH Overview 2. Frame Structure & Multiplexing Methods 3. Overheads & Pointers Page25

27 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) Page26

28 MSOH HPOH: VC-3/4 RSOH Overheads (Cont.) A1 A1 A1 A2 A2 A2 J0 X X J1 AU-PTR B1 E1 F1 X X D1 D2 D3 B3 C2 B2 B2 B2 K1 K2 G1 D4 D5 D6 D7 D8 D F2 D10 D11 D12 H4 S1 M1 E2 F3 Media dependent bytes (Radio-link, Satellite) X Reserved for National use Huawei propriety bytes V5 J2 N2 K4 LPOH: VC-11/12 K3 N1 Page27

29 A1 and A2 Bytes Framing Bytes Indicate the beginning of the STM-N frame Bytes are unscrambled A1 = f6h ( ), A2 = 28H ( ) STM-N: (3XN) A1 bytes, (3XN) A2 bytes STM-N STM-N STM-N STM-N STM-N STM-N Finding frame head Page28

30 A1 and A2 Bytes (Cont.) Frame Y Find A1,A2 Next process N OOF LOF AIS over 625μs (5 frames) over 3ms Page2

31 D1 ~ D12 Bytes Data Communications Channel (DCC) Bytes RS-DCC D1 ~ D3 12 Kbit/s (3x64 Kbit/s) MS-DCC D4 ~ D Kbit/s (x64 Kbit/s) NE NE NE NE NMT DCC channel OAM Information: Operation, Administration and maintenance Page30

32 E1 and E2 Bytes Orderwire Bytes E1 RS Orderwire Byte Used between regenerators E2 MS Orderwire Byte Used between multiplexers NE NE NE NE E1 and E2 Digital telephone channel E1-RS, E2-MS Page31

33 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) STM-N B1 Tx Rx BIP-8 A A A A #STM-N Calculate B 2#STM-N B #STM-N B1 = B Calculate B 1#STM-N Compare B & B RS-BBE Page32

34 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 Page33

35 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 Traffic Tx Rx Generate MS-FEBBE MS-REI Return M1 Find B2 bit errors Generate MS-BBE Page34

36 K1 and K2 (b1-b5) Bytes Automatic Protection Switching (APS) bytes I I I S I WTR Used for network multiplexing protection switch function S P P WTR P P Transmitting APS protocol Page35

37 K2 (b6 ~ b8) Byte Rx detects K2 (b6-b8) = "111 Start Generate MS-AIS alarm Tx detects K2 (b6-b8) = "110" Generate MS-RDI alarm Detect K2 (b6-b8) 111 Generate MS-AIS 110 Return MS-RDI Generate MS-RDI Page36

38 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). Page37

39 Path Overheads R S O H A U P T R M S O H Higher Order Path Overhead 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 Page38

40 J1 Byte Path trace byte The first byte of VC-4 Detect J1 User-programmable (HUAWEI SBS) The received J1 should N Match Y match the expected J1 HP-TIM Next process Page3

41 B3 Byte Path bit parity Verify B3 Even parity code Used to detect bit errors Mechanism is same as B1 and B2 N Correct Y HP-BBE Next process Page40

42 C2 Byte Signal label byte Detect C2 The received C2 should match with the expected C2 Specifies the mapping type in the VC-n Y Match N N 00H Y HP-UNEQ 00 H Unequipped 02 H TUG structure 13 H ATM mapping Next process HP-SLM Insert AIS downward Page41

43 Path Overheads V5 Low Order Path Overhead Indicated by TU-PTR 1 4 Error checking, Signal Label 1 V5 J2 N2 K4 and Path Status of VC-12 b1 - b2 Error Performance VC-12 VC-12 VC-12 VC-12 Monitoring (BIP-2) b3 Return Error detected in VC-12 (LP-REI) b8 Return alarm detected in VC-12 (LP-RDI) 500μs VC-12 multi-frame Page42

44 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 Page43

45 AU-PTR 1 RSOH Negative justification Positive justification 4 H1YYH2FF H3H3H MSOH RSOH μs 4 H1YYH2FFH3H3H MSOH μs Page44

46 TU-PTR TU Multi-frame 500μs H TU POINTERS H2 H3 VC3 VC- VC- VC- VC TU POINTERS V1 V2 V3 V4 Page45

47 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? Page46

48 Summary SDH Overview Frame Structure & Multiplexing Methods Overheads & Pointers Page47

49 Thank you