Download - 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
Page3Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page4Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page5Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page6Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page7Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page8Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page9Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page10Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. SDH Overview
2. Frame Structure & Multiplexing Methods
3. Overheads & Pointers
Page11Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page12Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page13Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page14Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page15Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page16Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page17Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page18Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
From 140Mb/s to STM-N
140MRate
adaptationAdd HPOH
C4
9
1 260125 μs
1
Next
Mapping
VC4
1
9
125μs1 261
HPOH
Page19Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
From 140Mb/s to STM-N
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
Page20Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
From 34Mb/s to STM-N
34M Rate Adaptation
Add LPOH
C3
1 84
9
125μs
1 1
9
VC3
LPOH
125μs1 85
Next
Mapping
Page21Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
From 34Mb/s to STM-N
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
Page22Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page23Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page24Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Questions
What are the main parts of SDH Frame structure?
What is the transmission rate of STM-4? How to calculate it ?
Page25Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. SDH Overview
2. Frame Structure & Multiplexing Methods
3. Overheads & Pointers
Page26Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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)
Page27Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page28Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page29Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
A1 and A2 BytesFrame
Nextprocess
FindA1,A2
OOF
LOF
N
Y
AIS
over 3ms
over 625μs (5 frames)
Page30Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page31Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page32Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page33Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page34Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page35Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page36Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page37Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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).
Page38Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page39Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page40Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page41Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page42Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page43Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page44Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page45Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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
Page46Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
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?
Page47Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Summary
SDH Overview
Frame Structure & Multiplexing Methods
Overheads & Pointers
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