Download - Training PPT,SDH Principle,20040423

Transcript
Page 1: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Basic Principles of SDH

Pre-sales Comm. And Tech. Support, OTPD

Pang Lipeng

Page 2: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OutlineOutline

▼ Overview to SDH

▼Rate and frame structure

▼Multiplexing structure and procedures

▼SDH network protection

▼ SDH network synchronization

Page 3: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OO//EE

Dem

ultip

lexing

Dem

ultip

lexing

EE//

OO

2Mbit/s2Mbit/s (( electrical signalselectrical signals ))

Add/drop 2Mbit/s signals Add/drop 2Mbit/s signals in PDH and SDH systemsin PDH and SDH systems

ADM155Mb/s 155Mb/sOptical

interface

2Mbit/s2Mbit/s (( electrical signalselectrical signals ))

Optical interface

Dem

ultip

lexing

Dem

ultip

lexing

Dem

ultip

lexing

Dem

ultip

lexing

Mu

ltiplexin

g M

ultip

lexing

Mu

ltiplexin

g M

ultip

lexing

Mu

ltiplexin

g M

ultip

lexing

Page 4: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SDH feature SDH feature -- plentiful overhead bytes-- plentiful overhead bytes

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.

Page 5: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

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.

Page 6: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OutlineOutline

▼ Overview to SDH

▼Rate and frame structure

▼Multiplexing structure and procedures

▼SDH network protection

▼ SDH network synchronization

Page 7: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SSDDHH level SSOONNEETT

115555MM

662222MM

22..55GG

1100GG

STM-1(1920CH)

STM-4

STM-16

STM-64

OC-3/STS3(1440CH)

OC-12/STS-12(8046CH)

OC-48/STS-48(32356CH)

OC-192/STS-192

155.520 Mbit/s

622.080 Mbit/s

2488.320 Mbit/s

9953.280 Mbit/s

Name

40G STM--256 OC-576 39813.120Mbit/s

SDH ratesSDH rates

level Standard rate

STM- Synchronous transfer mode

Page 8: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

9 rows

270 columns (byte)

1

2PAYLOAD

( with POH )

9 columns

SOH

AU-PTR

SOH( section overhead )

capacity = 9 ×270 bytes

8000 frames/s

STM-1 frame structureSTM-1 frame structure

Page 9: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SOH

SOH

AU pointer SDH payload

( with POH)

1

3

4

5

9

9270N bytes

9N

261 N

Transmission direction

STM-NSTM-N frame structure frame structure

125s

Frame period, frame frequency block and rate

Frame structureFrame structure

Page 10: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-1Signal “A”

STM-1Signal “B”

STM-1Signal “C”

STM-1Signal “D”

Byte in

terleaver mu

ltiplexer

STM-4 signal

(4×STM-1)

t

t

Byte interleave synchronous Byte interleave synchronous multiplexingmultiplexing

Page 11: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

1. Information payloads --They contain various information blocks and some POH bytes used for channel performance supervision, management and control.

2. 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.

3. 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.

Page 12: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SDH TM SDH DXC SDH TM

MS MS

PATH

RS RSRS

REG REG

Tributary signals

Tributary signals

VC multiplexing

VC demultiplexing

Path, MS and RS

SDH network segment modelSDH network segment model

Page 13: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

A1 A1 A1 A2 A2 A2 J0 * *

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D10 D11 D12

D7 D8 D9

S1 M1 E2

AU PRT

9 columns

9

rows

RSOH

MSOH

STM-1 SOH bytesSTM-1 SOH bytes

SOH bytesSOH bytes

Page 14: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

framing bytes: framing bytes: A1, A2 bytes identifies the initial location of the framA1, A2 bytes identifies the initial location of the frame. The byte code pattern are defined as e. The byte code pattern are defined as A1: 11110110 ( F6H ) A2: 00101000 ( 28H ) (transparent transmission)

RS trace byte: J0RS 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

Description for SOH byteDescription for SOH byte

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.

Page 15: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

•Data Communication Channel (DCC): D1—D12Data Communication Channel (DCC): D1—D12SOH 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 E2Orderwire channel: E1 and E2E1 and E2 offers the orderwire voice channel. E1 is used for the RS orderwire and E2 for the orderwire between terminals.

•User channel: F1User channel: F1It is for the network provider. It is used for the special maintenance of system operator, e.g., providing temporary 64kb/s data/voice channel.

Page 16: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

•B1: BIP-8B1 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-N24It 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.

Page 17: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

APS channel: K1 and K2 ( b1-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: S1 ( b5-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

Page 18: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

MS-REI: M1M1 is used for MS-REI. It sends the quantity of the bit errors checked out by B2.

Bytes 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.

STM-N(N>1) SOHIt 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.

Page 19: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-4 SOH bytesSTM-4 SOH bytes

15

36 byte

AU PRT9

rows

Page 20: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

A2 A2 A2

E1

D2

K1

D5

D11

D8

144 bytes

A1 A1 A1

B1

D1

B2 B2 B2

D4

D10

D7

S1

9 rows

F1

D3

K2

D6

D12

D9

E2

RSOH

A1

B2

A1

AU PRT

MSOH

M1 。。。

J0/C1 Z0/C1 Z0/C1

注:新协议中有些字节用作 FEC 功能

STM-16 SOH bytesSTM-16 SOH bytes

Page 21: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

A2 A2 A2

E1

D2

K1

D5

D11

D8

576 bytes

A1 A1 A1

B1

D1

B2 B2 B2

D4

D10

D7

S1

9 rows

F1

D3

K2

D6

D12

D9

E2

RSOH

A1

B2

A1

AU PRT

MSOH

M1 。。。

J0/C1 Z0/C1 Z0/C1

注:新协议中有些字节用作 FEC 功能

STM-64 SOH bytesSTM-64 SOH bytes

Page 22: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

FEC FEC (Forward Error Correction)(Forward Error Correction)

Some 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.

Page 23: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OutlineOutline

▼ Overview to SDH

▼Rate and frame structure

▼Multiplexing structure and procedures

▼SDH network protection

▼ SDH network synchronization

Page 24: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Multiplexing structure in G.707

STM-N× N × 1 140Mb/s

45Mb/s34Mb/s

6.3Mb/s

2Mb/s

1.5Mb/s

×3

× 7

×3

× 1× 3

C-11

C-12

C-2

C-3

C-4

VC-11

VC-2

VC-3

VC-3

VC-4

TU-11

TU-12

TU-2

TU-3

TUG-2

TUG-3

AUG

AU-3

AU-4

VC-12

×4 ×4

×1

Multiplexing

VC

C

TU

AU

TUGAUG

STM

Mapping Positioning

× 7 × 1× 7

Multiplexing structure and proceduresMultiplexing structure and procedures

Page 25: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

注 2: VC-2-mc 主要用于传输图象等业务,具体技术实施方法待定。大约是 4Mb/s34Mb/s 之间。而 SDH 可为其提供 VC-2 、 VC-2 的级联等方式来传输。 图 3.2

Mapping structure in ChinaMapping structure in China

Pointer processing

Positioning

Multiplexing

Mapping

STM-1 capacity: 1. 1×140M signal 2. 3×34M signals

3. 63×2M signals

Page 26: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

New multiplexing structure in G.707

Pointer processing

Positioning

Multiplexing

Mapping

Page 27: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Byte interleaving multiplexing and Byte interleaving multiplexing and byte block multiplexingbyte block multiplexing

Byte interleaving multiplexing:

(4×AUG-1 are multiplexed into 1×AUG-4)

Byte block multiplexing: When AUG-N (N 4), AUG-16 is≧

Byte block interleaving multiplexing:

Page 28: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

C-n

Multiplexing unitMultiplexing unit

1. Container (C)

C contains service signals at various rates.

G.707 specifies five standard containers for PDH rate series: C-11, C-12, C-2, C-3 and C4.

PDH series indicate the payload by H-n, which is divided into different levels.

Page 29: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

C-n

VC-n POH

VC supports the connection at the SDH path layer. VC, composed of payload (C output) and POH, is the information terminal of SDH path.

VC-n=C-n+VC-n POHVC-n=C-n+VC-n POH

LOVC: VC-1 and VC-2

VC-3 (VC-3 - TU-3 - TUG-3- VC-4)

HOVC: VC-4

VC-3 (in AU-3)

2. VC2. VC

Page 30: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Adjustment bit

Service/

PDH signal

=

POH

C

=VC

Service signal/PDH signal, C and VC

Page 31: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

VC parameters

VC VC-4 VC-3 VC-2 VC-12 VC-11

125 125 500 500 500

Structure 2619 859 4(129-1)

4(49-1) 4(39-1)

Capacity (byte number) 2349 765 428 140 104

Rate (Mbit/s) 150.336 48.960 6.848 2.240 1.664

Frame frequency and multiframe frequency (Hz) 8000 8000 2000 2000 2000

Frame period and multiframe (s)

Page 32: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

3. TU and TUG3. TU and TUG

TU adapts the low-order path signals into the high-order path layer (e.g., VC-4).

Four TUs are available, i.e., TU-n (n=11, 12, 2 and 3).

TU-n consists of a LOVC-n and a TU-n PTR.

TU-n =VC-n+TU-n PTR

TU-n PTR points the shift between VC-n payload start point and HOVC frame start point.

TUG is composed of one or several TUs at the fixed location of HOVC payload.

Page 33: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

4. AU and AUG4. AU and AUG

AU adapts the HO path signals into MS layer.

AU-3 and AU-4 are available.

AU-n (n=3, 4) comprises a HOVC-n and a AU-n PTR. For example:

AU-n =VC-n+AU-n PTR

AU-n PTR points the shift between VC-n payload start point and MS start point.

AUG is composed of one or several AUs at the fixed location of STM-N payload.

One AU is composed of one AU-4 or three AU-3 in the byte interleaving multiplexing mode.

Page 34: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

TU and AU parameters

TU and AU AU-4 AU-3 TU-3 TU-2 TU-12 TU-11

8000 8000 8000 2000 2000 2000

Structure 2619+9819+3 859+3 4(129)

4(49) 4(39)

Capacity (byte number) 2358 786 768 432 144 108

rate ( Mbit/s ) 150.912 50.304 49.152 6.912 2.304 1.728

125 125 125 500 500 500Frame frequency and multiframe fr

equency (Hz)

Frame period and multiframe (s)

Page 35: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Multiplexing step 1 Multiplexing step 1 -mapping-mapping

Mapping synchronizes tributary signals with the corresponding VC so that VC can send, multiplex and cross signals independently. (Only STM-1 has the mapping function.)1. Mapping modeThe mapping can be divided into asynchronous mapping and synchronous mapping by the synchronization state between mapped signals and SDH network.Asynchronous mapping --The pointer adjusts the payload to adapt the signals into SDH frame, independent of signal features and network synchronization. The pointer adjusts the frequency or phase difference to synchronize the signals without slide buffer. As a common mapping mode, it is necessary in the long transition from PDH to SDH.

Page 36: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Synchronous mapping --The mapped signals must be strictly synchronous with SDH network. 125us (the duration of one frame) slide buffer is required to reduce the slide loss in the synchronization. The slide buffer causes 150us delay to the multiplexer, but 10us delay to the demultiplexer.

Synchronous mapping are categorized as bit synchronous mapping and byte synchronous mapping.

Page 37: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Comparison between asynchronous mapping

and synchronous mapping

Bit synchronous

Synchronous mapping

characteristics

Mapping node

Asynchronous mapping

Byte synchronous mapping

It is a common mode, independent of signal features, network synchronization and slide buffer. The minimum delay caused is 10us. The primary group mapping can not access directly N×64kb/s signals because the de-framing is required. The interface is simple.

It is independent of signal features, but it requires the network synchronization and 125us slide buffer. The delay caused is more than 125us (multiplexer). N×64kb/s signals can not be accessed directly because the de-framing is required. The interface is comparatively simple.

2Mb/s signals should be framed according to G.704. It requires the network synchronization and 125us slide buffer. The delay caused is more than 125us (multiplexer). N×64kb/s signals can be accessed directly because the de-framing is not required. The interface is the most complex.

Page 38: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

VC-4 PAYLOAD

260 columns (byte)

HP-POH9 rows×1 column

J1

B3

C2

G1

F2

H4

F3

K3

N1

C-4 is mapped into VC-4C-4 is mapped into VC-4

Page 39: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

1. Add VC-4 POH

2. HPOH

J1: Path trace byte

It repeatedly sends the HP access point identifier whose content is decided by the transmitter and receiver, thus the transmitter may confirm the connection with the specified receiver. J1 location is pointed by the related pointer.

B3: Path BIP-8 code

It comes from the interleaving parity calculation of all VC-4 bits before scrambling.

Page 40: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

F2 and F3: Path user byte

They offers the orderwire communication between path units.

H4: TU indication byte

It indicates the payload multiframe type and payload location.

K3 (b1-b4): APS path byte

It sends HP APS signals.

K3 (b5-b8): For future use (backup)

N1: Network operator byte

It monitors the HP serial connection.

Page 41: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Multiplexing step 2 Multiplexing step 2 -Positioning-Positioning

Positioning refers to a process to take the frame deviation information into TU or AU, that is, TU PTR (AU PTR) attached to VC indicates and determined the LOVC frame start point in the TU payload ( the HOVC frame start point in the AU payload.

SDH pointer function:

•When the network works synchronously, the pointer aligns the phases of synchronous signals.

•When the network dismatches, the pointer aligns the frequencies and phases. When the network is out of synchronization or works asynchronously, the pointer traces and aligns the frequencies.

•The pointer can also accept the frequency jitter and wander in the network.

Page 42: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

AU-4=VC-4+AU-4 PTR

TU-3=VC-3+TU-3 PTR

AU-4 PTR=H1 , Y , Y , H2 , 1* , 1* , H3 , H3 ,H3

Y=1001SS11 : SS --bit without specific value

1*=11111111

TU-3 PTR=H1 , H2 , H3

VC-4/VC-3 positioning in AU-4/TU-3

Page 43: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Multiplexing step 3 Multiplexing step 3 -synchronous multiplexing-synchronous multiplexing

Multiplexing refers to the adaption of several LP signals (TU-12) into HP signals (VC4) or several HP signals (AU-4) into STM-N frame, that is, adapt TU into VC or AU into STM-N in the byte interleaving mode.

For example: TU12(×3) → TUG2(×7) → TUG3(×3) → VC4

For example: AU-4(×1) → AUG(×N) → STM-N

As VC tributaries are synchronous due to TU and AU pointers, the process is called the synchronous multiplexing.

Multiplexing mode: Byte interleaving mode.

Page 44: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-1signal “A”

STM-1signal “B”

STM-1signal “C”

STM-1signal “D”

STM-4 signal

(4×STM-1)

t

t

Byte interleave synchronous Byte interleave synchronous multiplexingmultiplexing

Byte in

terleave mu

ltiplexer

Page 45: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

#1

1 261

1 9

AUGAUG

123…N 123…N

123…N 123…N

N 9 N 261

#2

1 261

1 9

AUGAUG

STM-N

#N

1 261

1 9

AUGAUG

For example: Multiplex N×AUG into STM-N

Page 46: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

TS0 TS1 TS2 TS15 TS16 TS17 TS18 TS31

2048kbit/s frame

32

R 1

R 32

R 1

R 32

R 1

R 32

R 1

R

C-12 frame

V5 K4N2J2

VC-12 frame

V1 V2 V3 V4

99

TU-12 frameC-12 multiframe

Multiplex 2Mbit/s into STM-1 (1)

Page 47: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

3 个 TU-12 通过字节间插复用成 1 个 TUG-2 的信息结构

TUG-2 information structure

99

1212

2

b

1 2 3 1 3 1 2 3

ca cba

TU-12 a

TU-12 b

TU-12 c

4 4 4

Multiplex 2Mbit/s into STM-1 (2)

Page 48: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Multiplex 7×TUG-2 into 1 × TUG-3 in the byte interleaving mode

TUG-3 information structure

99

84848686

TUG-2 ( 1 ) TUG-2 ( 2 ) TUG-2 ( 7 )

12

34

5

6

7

1

23

45

6

7

12

34

5

6

7

1

23

45

6

7

Insert bytes

1

2

1

2

3

1

2

3

1

2

33

1

2

1

2

3

1

2

3

1

2

33

1

2

1

2

3

1

2

3

1

2

33

Multiplex 2Mbit/s into STM-1 (3)

Page 49: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

C4 structure

Multiplex 2Mbit/s into STM-1 (4)

Multiplex 3×TUG-3 into C4 in the byte interleaving mode

Page 50: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

In order to supervise the 140Mb/s path signals, it is required in the multiplexing to add a column of VC4 POH before C4 frame. Then the signals is in the VC4 structure.

VC-4 PAYLOAD

260 columns (byte)

HPOH9 rows×1 column

J1

B3

C2

G1

F2

H4

F3

K3

N1

Map C-4 intoVC-4

Multiplex 2Mbit/s into STM-1 (5)

Page 51: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

VC-4 PAYLOAD

261 columns (byte)

J1B3C2G1F2H4F3K3N1

H1 H2 H3 H3 H3Y Y 1 1

AU-4 PTR consists of 9 bytes from column 1~9 at row 4 of AU-4 frame.

Add AU-PTR to VC-4 to make VC-4 become AU-4.

Multiplex 2Mbit/s into STM-1 (6)

Page 52: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-1 PAYLOAD

RSOH

AU-PTR

MSOH

POH VC-4 PAYLOAD

261 column

9 rows×1 column

9 rows

Add RSOH and MSOH to form STM-1.

Multiplex 2Mbit/s into STM-1 (7)

Page 53: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-N

× N × 1C-12VC-12VC-4 TUG-2AUG-4 AU-4 TU-12 2Mb/s

code speed

adjustment

LD POH

TU PTR

AU PTR × 3 multiplexing

×7 multiplexingHD POH

× 3 multiplexing

×N multiplexing

TUG-3

Mapping and multiplexing diagram

Page 54: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

STM-N

× N × 1C-12VC-12VC-4 TUG-2AUG-4 AU-4 TU-12 2Mb/s

2.048Mbit/s

2.176Mbit/s

2.240Mbit/s

2.304Mbit/s49.536Mbit/s

155.520Mbit/s

TUG-3

150.336Mbit/s

6.912Mbit/s

150.912Mbit/s

STM-1 rate adjustment

Page 55: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Layer standard

Multiplexing Positioning Mapping

STM-N

STM-1

AU-4

VC-4

TUG-3,2

TU-12

VC-12

C-12

Service Telephone and database

Page 56: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OutlineOutline

▼ Overview to SDH

▼Rate and frame structure

▼Multiplexing structure and procedures

▼SDH network protection

▼ SDH network synchronization

Page 57: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Link

Star

Tree

Ring

Mesh

SDH network topology

Page 58: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Self-sealing: When a fault occurs to the network, the service transmission can recover automatically in such a short time that a user can not find it.

Redundant Cross function

intelligence

Network self-healing

SDH network protection and self-healing

Page 59: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

MS 1+ 1 protection

MS 1: 1 protection

MS 1: n protection

( n<=14)

2-fiber unidirectional path protection ring

2-fiber unidirectional MS protection ring

2-fiber bidirectional MS protection ring

4-fiber bidirectional MS protection ring

Link network

Ring network

Dual-Node interconnection (DNI)

SDH network protections

Page 60: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SDH ring protections

Ring protection categorization:

By fiber quantity: 2-fiber and 4-fiber

By service direction: Unidirectional and bidirectional

By protection object level: Path protection and MS protection

Common ring protection:

2-fiber unidirectional path protection ring

2-fiber unidirectional MS protection ring

2-fiber bidirectional MS protection ring

4-fiber bidirectional MS protection ring

Page 61: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Several definitions

There are two kinds of SDH protection switching ring: MS protection switching ring and path protection switching ring. What are the most commonly used are 2-fiber unidirectional path protection ring, 2-fiber unidirectional MS protection ring, 2-fiber bidirectional MS protection ring and 4-fiber bidirectional MS protection ring. Before the principles of these rings is described in detail, several definitions should be explained: MS protection switching, path switching, unidirectional ring and bidirectional ring.

What are MS and path? Simply speaking, MS refers to the section between two multiplexers (or the equipment with multiplexing functions), and the multiplexed low-rate signals are called the path.

An extra channel is required to protection signals in the transmission. For the MS switching ring, the protection are based on MS, the switching depends on the MS signal quality between a pair of nodes, and all MS services are switched to another channel in the switching. However, for the path switching ring, the protection is based on path, and the switching depends on the quality of one channel.

Page 62: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Unidirectional ring Bidirectional ring

Unidirectional ring and bidirectional ring

Page 63: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

a ) in normal case b ) in abnormal case

P

W

A

B

C

D

P

W

A

B

C

D

倒换

2-fiber unidirectional path protection ring

Page 64: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Working principles of 2-fiber ring

Two fibers respectively form internal ring and external ring. One fiber is used to transmit service signals and the other to protect them. The two rings are unidirectional and transmit services in different directions. The tributary signals from node A to node C are transmitted simultaneously in two fibers and reach C in different direction at one time. C receives the signals of one fiber with better signal quality. If the connection from A to C breaks off, the signals in W fiber will be lost, the switch will be switched from W fiber to P fiber and receives the signals in P fiber. Thus the signals from A to C go on transmission.

Page 65: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Working principles of 2-fiber ring

A ring has 4 fibers: Two service fibers (one for receiving and the other for transmitting), and two protection fibers (one for receiving and the other for transmitting). Each fiber has a changeover switch. The signals transmit from A to C via W1 fiber clockwise, and the signals transmit from C to A via W2 fiber anticlockwise. This is a bidirectional ring and the two protection fibers are idle. When the connection from A to C breaks off, the changeover switches at B and C connect W1 to P1 and W2 to P2, ensuring the continuity of the ring.

In a 4-fiber ring, the transmission directions of W1 and P2 are the same, and so are those of W2 and P1. W1 and P2 can be integrated into one fiber W1/P2, and W2 and P1 into one fiber W2/P1. A half of W1/P2 timeslots transmit services, and the other half are idle in the normal case and protect W2/P1 services in the faulty case. A half of W2/P1 timeslots transmit services, and the other half are idle in the normal case and protect W1/P2 services in the faulty case. Thus a 4-fiber ring is simplified into a 2-fiber ring.

One half of W1/P2 timeslots transmit signals from A to C clockwise and the other half is idle. When the connection between A and C breaks off, the changeover switches at B and C connect the two fiber together. With the timeslot switching technique, the signals are switched from the service timeslot of one fiber to the idle protection timeslot of the other fiber.

Page 66: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

4-fiber bidirectional MS shared protection ring

a) In the normal case b) Switching in the faulty case

Page 67: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

2-fiber bidirectional MS shared protection ring

a) In the normal case b) Switching in the faulty case

Page 68: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Features and applications of self-healing rings

Advantage: The protection can be implemented easily. No APS protocol is required and the switching is the fastest (<30ms)

Shortcoming: The timeslots between nodes can not be used repeatedly, so the ring transmission capacity is small. And extra services can not be transmitted.

Ring transmission capacity: STM-N

Note: The unidirectional path protection ring found a wide application. It is applied to the centralized services.

Page 69: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

4-fiber bidirectional MS protection ring

Advantage: The timeslots between nodes can be used repeatedly, so the ring transmission capacity is large. And extra services can not be transmitted via the standby fibers P1 and P2.

Shortcoming: The switching is slow because APS protocol and cross connection are required. And the equipment should meet some high requirements.

Ring transmission capacity: k×STM-N (k is the node quantity in the ring)

Note: ADM equipment in a 4-fiber ring should meet some requirements, e.g., system capacity, cross capacity and software function. It is applied to the distributed services.

Page 70: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

2-fiber bidirectional MS protection ring

Advantage: The timeslots between nodes can be used repeatedly, so the ring transmission capacity is large. And extra services can not be transmitted via the standby fibers P1 and P2.

Shortcoming: The switching is slow because APS protocol and cross connection are required. And the equipment should meet some high requirements.

Ring transmission capacity: k/2×STM-N (k is the node quantity in the ring)

Note: The bidirectional MS protection ring found a wide application. It is applied to the distributed services.

Page 71: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

item Unidirectional path ring 2-fiber MS ring 4-fiber MS ring

node

Line rate

ring transmission capacity

APS protocal

swiching time

node cost

system complexity

k k k

STM-N STM-N STM-N

STM-N k/2×STM-N k×STM-N

no yes yes

30ms 50-200ms 50-200ms

low medium high

simple complex complex

Access network and relay net work

(centralized service)

Relay network and toll network (distributed

service)

Relay network and toll network (distributed

service) applications

Characteristics and applications of 3 protection rings

Page 72: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

A

B(primary) D(secondary)

C(primary)

E(secondary)

F

The services from A to F are transmitted in two ways: ABCF or ABDECF.

DNI, based on ITU-T G.842, is very practical to the services across rings.

DNI protection

Page 73: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

OutlineOutline

▼ Overview to SDH

▼Rate and frame structure

▼Multiplexing structure and procedures

▼SDH network protection

▼ SDH network synchronization

Page 74: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Synchronization

The synchronization is the nervous system of SDH network.

The asynchronization between NEs in one network leads to the unaligned timeslots and no proper connection between transmitter and receiver.

The asynchronization between networks leads to the broken network communication and service disconnection.

Page 75: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

4-level clocks in ITU-T recommendation

• Reference master clock — In compliance with G.811.

• Transit exchange clock — In compliance with G.812 (transit clock at the intermediate exchange)

• End exchange clock — In compliance with G.812 (local exchange clock)

• SDH NE clock — In compliance with G.813 (clock embedded in SDH NE)

Page 76: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Clock type

1. Caesium atom clock: It has the high long-term frequency stability and precision. The long-term frequency deviation is better than 1*10E-11, but the short-term stability is not good.

2. Quartz crystal oscillator: It has cheap clock source and high reliability, but low long-term frequency stability.

3. Rubidium atom clock: Its stability, precision and cost is between the above clocks. The adjustable frequency range is larger than caesium atom clock, the long-term stability is lower by about one magnitude, but it has excellent short-term stability, low cost and 10-year service life.

Page 77: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Synchronization mode

1. Full-synchronization mode: The overall network is synchronous with the unique PRC. Its synchronization is highly precise but difficult. In the implementation the hierarchical control scheme is usually adopted, that is, the hierarchical master/slave synchronization mode.

2. Pseudo-synchronization mode: The overall network is divided into several sub-networks, and the master clocks of the sub-networks comply with G.811. The slave clock is synchronous with the master clock in the sub-network. The clocks of the sub-networks are independent of each other, but the differences are so small that they are approximately synchronous.

Page 78: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

3. Quasi-synchronization mode: After the external timing reference is lost, the node clock holds on. The network synchronization quality is not good.

4. Asynchronization mode: The node clocks are different from each other in the synchronization, and the service can not go on normally, so the alarm signals are sent.

SDH network adopts the hierarchical master/slave synchronization mode at present.

Synchronization mode

Page 79: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Three working modes of slave clock in master/slave synchronization mode

Normal working mode – Upper-level clock tracing and locking mode

The clock reference, traced and locked by the slave site, comes from the upper-level site. It may be the master clock in the network, the clock from the clock source embedded in the upper-level NE, or the GPS clock at the local area. Comparing with the other two working modes of the slave clock, this mode is the most precise.

Hold-on mode

After all timing references are lost, the slave clock is in the hold-on mode. The slave site clock source uses the last frequency information, stored before the timing reference signal is lost, as the timing reference. That is to say, the slave clock has the “memory” function. The function can offer the timing signal complying with the original timing reference, ensuring that the slave clock frequency has a small deviation from reference clock frequency in a long time. This mode is less precise than the normal working mode. The equipment employs the memorized synchronization information, stored before 24 hours, to keep the synchronization state. The precision is required to be 0.37ppm.

Page 80: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Free-run mode – free-oscillation mode

When the slave clock loses all external timing references and timing reference memory, or works in the hold-on mode for a very long time, the oscillator in the slave clock will work in the free-oscillation mode. This mode is the worst precise. After the memorized synchronization information, stored in the equipment, has been used for 24 hours, the synchronization signals generated by the internal oscillator are used as synchronization signal. The precision is required to 4.6ppm.

Page 81: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Synchronization network of China Telecom

The digital synchronization network of China Telecom integrates the hierarchical master/slave synchronization and pseudo-synchronization, that is, the distributed timing mode.

1. PRC complying with G.811 in Beijing hierarchically controls the clocks until the lowest-level slave clock, which adopts the hierarchical master/slave synchronization mode.

2. This nation is divided into several synchronization areas. Each area has one LPR – rubidium atom clock. LPR can receive PRC signals or GPS signals. There are small differences in LPR between synchronous areas, but the differences are so small that they are approximately synchronous. So it is called the pseudo-synchronization mode.

As shown in the figure, the slave clock is in Wuhan. When a fault occurs to the master clock (Beijing), the slave clock will replace the master clock.

Page 82: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Master clock (Beijing)

Slave clock (Wuhan)

Regional reference clock

1

Regional reference clock

2

Provincial exchange

provincial exchange

市 局 市 局

GPS GPS

synchronization area 1

LPR

PRC

synchronization area 2

Page 83: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

G.811

G.812

G.812

G.812

No.1 transit exchange

No.2 transit exchange

No.K transit exchange

} N×G.813 SDH equipment clock

note: K=10;

N=20;

NE clock quantity < 60

SDH synchronization network -synchronization reference link

} N×G.813 SDH equipment clock

} N×G.813 SDH equipment clock

Page 84: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Synchronization scheme

General principle

Reduce the timing reference transmission length.

The controlled clock obtains the timing from higher-level clock.

The node clock quantity in a synchronization reference link is not more than 60.

Configure more than one external timing references.

Prevent the timing loop – make full use of S1 byte.

Timing information transmission – Obtain the timing from STM-N.

Page 85: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SSM and S1 byte

SSM

SSM (Synchronization Status Message) directly reflects the synchronous timing signal level in the synchronous timing transfer link. The messages can be used to judge the quality level of the synchronous timing signal received so as to control the operation state of the local node clock, e.g., continue tracing the signal, switch the input reference signal or change to the hold-on state.

Page 86: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

SI b5~b8 Clock level

0000 Unknown quality

0010 G.811 reference clock

0100 G.812 transit exchange slave clock

1000 G.812 local exchange slave clock

1011 SETS

1111 Not for clock synchronization

Note: other utilizations are reserved.

How to use S1 byte

ITU-T G.707 specifies SSM coding mode of STM-N interface, which is shown with MS overhead byte S1 b5~b8.

Page 87: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Timing protection switching and recovery

The equipment has more than 2 external synchronization signal input interfaces.

A) Timing protection switching function

When the high-level external synchronization source fails, the equipment can automatically switch to the low-level external synchronization source.

B) Recovery function

When the high-level external synchronization source return to normal, the equipment can obtain the timing signals from the high-level external synchronization source.

Page 88: Training PPT,SDH Principle,20040423

Internal Use Only▲

<ZTE corporation copyright reserved,No spreading abroad>

Thank you!