SDH Theory

SDH Theory

2Prepared by Tx-TAC

Chapter – 1 SDH Theory

Objectives

• Introduction to SDH– Multiplexing– STM-1 frame– Virtual Containers (VCs)– TU coordinates– STM-N frame– SDH layers and trails– SDH network elements– SDH overhead– Mapping

3Prepared by Tx-TAC


What is SDH?• SDH = Synchronous Digital Hierarchy• It is a transport network

– synchronous– fully standardized– with high bandwidth– for synchronous and asynchronous signals– for future broadband signals and new services– with standardized network management capabilities– with traffic protection– with a flexible multiplexing structure

• direct access to tributaries• cross-connections without demultiplexing

4Prepared by Tx-TAC


Digital Transmission System

• Regenerator– recreates the signal.

• Multiplexer (MUX)– Multiplexer combines data from

several lines and transmits itover a higher-capacity data link.

No signal

60 km

R

60 km

Regenerator

MUX MUX

5Prepared by Tx-TAC


• Add-Drop Multiplexer (ADM)– Part of the traffic is terminated.– Part of the traffic goes transparently

through.

Multiplexer Naming Conventions

TMm/n

aggregate

tribut arie s

ADMm/n

aggregateaggregate

tributaries

• Terminal Multiplexer (TM)– All traffic is terminated here.– m: aggregate level– n: lowest tributary level

6Prepared by Tx-TAC


• No traffic is terminated.• Cross-connection matrix

connects tributary signals of one aggregate to another aggregate.

Digital Cross-connect (DXC m/n)

PDHMUX

PDHMUX

PDHMUX

PDHMUX

DDF

SDHCross-Connect

7Prepared by Tx-TAC


PDH vs. SDH — Bit Rates

SONET(ANSI)

SDH(ITU-T)

Data rate(Mbps)

STS-1 51.84STS-3 STM-1 155.52STS-9 466.56STS-12 STM-4 622.08STS-18 933.12STS-24 1244.16STS-36 1866.24STS-48 STM-16 2488.32

STM-64 9953.28

Hierarchy level USA Europe0 64 kbit/s T0 64 kbit/s E01 1.544 Mbit/s T1 (24x) 2.048 Mbit/s E1 (32x)2 6.312 Mbit/s DS-2 (4x) 8.448 Mbit/s E2 (4x)3 44.736 Mbit/s DS-3 (7x) 34.368 Mbit/s E3 (4x)4 139.264 Mbit/s E4 (4x)

E1E0

E2E3

E4plesiochronous

plesiochronous

plesiochronous

synchronous

TM STM-1

TM STM-4

TM STM-16

• E1 (2.048 Mbit/s)

• T1 (1.544 Mbit/s)

• DS-2 (6.312 Mbit/s)

• E3 (34.368 Mbit/s)

• DS-3 (44.736 Mbit/s)

• E4 (139.264 Mbit/s)

• ATM

• etc.

PDH

SDH

8Prepared by Tx-TAC


PDH vs. SDH — Add & Drop Function

ADM STM-4STM-4

Six TMs neededto drop E1

One ADM isenough to drop E1.

TM TM

TMTM

TMTM

E3

E3

E3

E2

E2

E1

E1

E1

E4 E4

E1 (2.048 kbit/s)

E2

2/1 2/1

3/23/2

4/3 4/3

PDH SDH

9Prepared by Tx-TAC


STM-1 Frame

2430 bytes/frame × 8 bit/byte × 8000 frame/s = 155.52 Mbit/stransmitted from top to bottom and left to right

AU-4 pointers

MSOH

PayloadVC-4 (HO-VC)

RSOH

9 ro

ws

(byt

es)

9

5

261

270 columns (bytes)

3

10Prepared by Tx-TAC


155.520 Mbit/s serial signal

9 BYTES + 261 BYTES = 270 BYTES 270 BYTES x 9 = 2430 BYTES

2430 BYTES/FRAME x 8 BITS/BYTE x 8000 FRAMES/SEC = 155.520 Mbit/s

125us

1 2 3 4 5 6 7 8 9

2430 b yte s

261 b yte s9 b yte s 261 b yte s9 b yte sO ve rhe a d p a y lo a d

F F F F

261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s261 b yte s9 b yte s

STM -1 Frame



C4 4. level 140 Mbit/s

C3 3. level 34/45 Mbit/s

C2 2. level 6 Mbit/s

C1.2 1. level 2 Mbit/s

C1.1 1. level 1.55 Mbit/s

E4 (139.264 Mbit/s)

Virtual Containers (VCs)

VC-3

VC-4

VC-12VC-11

VC-2

E1 (2.048 Mbit/s)T1 (1.544 Mbit/s)

DS-2 (6.312 Mbit/s)

E3 (34.368 Mbit/s)

DS-3 (44.736 Mbit/s)

ATM cells

Mapping



VC-4STM-N× N

× 3× 1

× 3

× 7

139 264 kbit/s

44 736 kbit/s34 368 kbit/s

6312 kbit/s

2048 kbit/sPointer processing

Multiplexing

Aligning

Mapping1544 kbit/s

CTPpassing connectionContains: payload pointer...

TTPend of trailContains: path trace,

signal label, error detection…

AUG AU-4

TUG-3

TUG-2

TU-3

TU-2

TU-12

VC-2

VC-3

VC-12

VC-11

C-4

C-3

C-2

C-12

C-11

× 1

C-n Container-n

SDH Multiplexing Structure (ETSI)

× 1

ITU-T



VC-4STM-N× 1× N

× 3

× 3× 1

× 3

× 4

× 7× 7

139 264 kbit/s

44 736 kbit/s34 368 kbit/s

6312 kbit/s

2048 kbit/sPointer processing

Multiplexing

Aligning

Mapping1544 kbit/s

• TTP– end of trail– Contains: path trace,

signal label, error detection…

• CTP– passing connection– Contains: payload pointer...

AUG

AU-3

AU-4

VC-3

TUG-3

TUG-2

TU-3

TU-2

TU-12

VC-2

VC-3

VC-12

VC-11

C-4

C-3

C-2

C-12

C-11

× 1

TU-11

C-n Container-n

SDH Multiplexing Structure (G.707)



KLM: 300

KLM CoordinatesAU-4 pointers

MSOH

PayloadVC-4 (HO-VC)

RSOH

VC-4

POH

VC-12

VC-12

K

L

TU12-1 TU12-2 TU12-3

TUG3-1 TUG3-2 TUG3-3

TUG2-6

TUG2-7

TUG2-5

TUG2-4

TUG2-3

TUG2-1

TUG2-2

TUG-3 number (values 1-3)TUG-2 number (values 1-7)TU-12 number (values 1-3)

KLM: 271KLM: 152

VC-3



STM-N Frame

T1518000-95

4

3

1

9

5

270 × N columns (bytes)

9 × N 261 × N

STM-N payload9 rows

Section overheadSOH

Section overheadSOH

Administrative unit pointer(s)

• One SOH• AU pointers for every VC-4• N × VC-4s

Synchronous TransportModule

Line RateMbit/s

STM-1 155.520

STM-4 622.080

STM-16 2488.320

STM-64 9953.280



Multiplexing of AU into STM-N

AUG

AUG

AUG

AUG

STM-4

SOH

AU-4

AU-4

AU-4

AU-4



SDH Layers

PSTN ISDN ATM IP

Lower-Order

Higher-Order

Multiplex

Regenerator

Physical

Client

Server

OS, ES

RS

MS

HOP (VC-4)

LOP (VC-12, VC-3)



Client

Server

SDH Layers



R R

LO Path

MS trail MStrail

RStrail

RStrail

RStrail

RStrail

MS trail

TM LO TM LOADM HO DXC LO

HO Path HO Path

SDH Trails 1(2)

• Trail: Route between two Trail Termination Points (TTP) • TTP: Point where signal is terminated• RS trail: Regenerator Section trail (or just RS) is between regenerators• MS trail: Multiplex Section trail (or just MS) is between multiplexers• Path (P): Trail in path layer (HOP or LOP)

RStrail



SDH Trails 2(2)

HO

LO

MS

RS RS RSRS RS RS RS

MS MS MS MS

HO HO

RS RS RS

MS

HO

LO

RS trail RS trail RS trail RS trail RS trail

MS trail MS trailMS trail

HO path HO path

LO path

LO matrix LO matrix

HO matrix



• Regenerates the optical signal.

• Terminates RSOH.

REGSTM-N STM-N

Regenerator



Terminal Multiplexer

TMSTM-N

orPDH

STM-M

• Terminates RSOH and MSOH.

• May terminate HOP and LOP overhead.

• Multiplexes/maps tributary signals.

• Includes timing and management functions.



STM-N or PDH

STM-MSTM-M

ADM

Add/drop Multiplexer

• Terminates RSOH and MSOH.• May terminate HOP and LOP overhead.• Includes connection function between the two aggregates.• Multiplexes/maps tributary signals.• Includes a connection function for allocation of TUs within the STM

frame. • Includes timing and management functions.



Cross-connect

• Terminates RSOH and MSOH.• Includes connection function between the aggregates.• Can have tributary ports, for which it may terminate HOP and LOP

overhead.• Includes timing and management functions.

STM-N or PDH

STM-MSTM-M DXC



STM-16

STM-4

STM-1

STM-16

STM-4

STM-1

SDXC 4/1Example of Cross-connect (XC)

16 x

4 x

1 x

16 x

4 x

1 x

SDH multiplexer

AUG

VC-4

34 (45) Mbit/s2(1.5) Mbit/s

VC-12 VC-3

HOXC

LOXC



SDH Overhead

• Overheads carry information for monitoring, maintaining and controlling the operation of network.

• Overhead types– POH for end-to-end monitoring of payload signal (VC-12, VC-3 and VC-4)

• Block errors, far end alarms, trace and payload type– SOH is used for monitoring of signal between SDH equipment.

• RSOH: block errors, trace and TMN communication• MSOH: block errors, synchronization, TMN communication and far-end

alarms

POH

RSOH

MSOH

POINTER

9 260

270

3

5

9



1 2 3 4 5 6 7 8 9RSOH 1 A1 A1 A1 A2 A2 A2 J0 NU1 NU2RSOH 2 B1 R1 R2 E1 R3 U1 F1 NU3 NU4RSOH 3 D1 R4 R5 D2 R6 U2 D3 U3 U4PTR 4 H1 Y1 Y2 H2 1 1 H3 H3 H3

MSOH 5 B2 B2 B2 K1 U5 U6 K2 U7 U8MSOH 6 D4 U9 U10 D5 U11 U12 D6 U13 U14MSOH 7 D7 U15 U16 D8 U17 U18 D9 U19 U20MSOH 8 D10 U21 U22 D11 U23 U24 D12 U25 U26MSOH 9 S1 Z12 Z13 Z21 Z22 M1 E2 NU5 NU6

RSOH

– A1, A2 framing patterns (F6H), (28H)– J0 regenerator section Trail Trace Identifier (TTI)– B1 BIP-8 parity byte– E1 RS orderwire channel (service telephone)– F1 user (network operator) data channel– D1, D2, D3 regenerator section Data Communication Channel (DCCR)– NU1, NU2, NU3, NU4 bytes reserved for national use– R1, R2, R3, R4, R5, R6 media specific bytes (e.g. radio link)– U1, U2, U3, U4 bytes with no defined use



MSOH

– B2 BIP-24 parity bytes– K1, K2 Automatic Protection Switching (APS) channel, bit oriented

protocol (bits 1-5), Remote Defect Indication (RDI) (bits 6-8)– D4 to D12 multiplex section Data Communication Channel (DCCM)– S1 synchronization status (bits 5-8)– M1 Remote Error Indication (REI)– E2 MS orderwire channel (service telephone)– NU5, NU6 bytes reserved for national use– U5 to U26 bytes with no defined use– Z12, Z13, Z21, Z22 bytes with no defined use

1 2 3 4 5 6 7 8 9RSOH 1 A1 A1 A1 A2 A2 A2 J0 NU1 NU2RSOH 2 B1 R1 R2 E1 R3 U1 F1 NU3 NU4RSOH 3 D1 R4 R5 D2 R6 U2 D3 U3 U4PTR 4 H1 Y1 Y2 H2 1 1 H3 H3 H3

MSOH 5 B2 B2 B2 K1 U5 U6 K2 U7 U8MSOH 6 D4 U9 U10 D5 U11 U12 D6 U13 U14MSOH 7 D7 U15 U16 D8 U17 U18 D9 U19 U20MSOH 8 D10 U21 U22 D11 U23 U24 D12 U25 U26MSOH 9 S1 Z12 Z13 Z21 Z22 M1 E2 NU5 NU6



VC-4 and VC-3 POH

POHJ1B3C2G1F2H4F3K3N1

REI RDI Reserved Spare

1 2 3 4 5 6 7 8

J1 Trail Trace IdentifierB3 Parity BIP-8C2 Signal label (C2), used for payload type identificationG1 Path status

REI Remote Error IndicationRDI Remote Defect Indication

F2 Network operator (user) channelH4 Multiframe indicator, a sequence indicating TU-multiframe

phase (position of VC-12/VC-2)F3 Network operator (user) channelK3 Automatic Protection Switching (bits 1-4)N1 Tandem Connection Monitoring TCM, optional use in

multioperator environments



VC-2 and VC-12 POH

J2 Trail Trace IdentifierN2 Tandem Connection Monitoring TCM, optional use in multioperator

environmentsK4 Automatic Protection Switching (bits 1-4), additional

information for RDI (bits 5-7) (optional)V5 Signal monitoring

Parity BIP-2Remote Error Indication (REI)Remote Failure Indication (RFI), only for VC-11 (not in ETSI)Signal label (SL)Remote defect indication (RDI)

POHV5 J2 N2 K4

V51 2 3 4 5 6 7 8BIP-2 BIP-2 REI RFI SL SL SL RDI



PDH over SDH

2 Mbit/s plesiochronous stream`

Justification bytes

C12POH

Path OverheadVC12

Container

POH

TU PointerTU12

Virtual Container

• Container (C)– basic payload unit

• Virtual Container (VC)– C + POH (path overhead)

• Tributary Unit (TU)– VC + pointer– The pointer indicates the start

of the VC and allows dynamic alignment of the VC within the TU frame.



Asynchronous Bit synchronous Byte synchronous

PDH signal is notsynchronized with SDH

PDH and SDH aresynchronized but not the

PDH frame (if any)

PDH and SDH aresynchronized and also the

PDH frame

Justification neededaccess to 2048 kbit/s In SONET only Direct access to

64 kbit/s signal

Defined for:139M, 45M, 34M,

6M, 2M, 1.5M

Defined for:6M, 1.5M

Defined for:2M, 31×64 kbit/s, 1.5M

Mapping

• Mapping is a process where tributaries (Containers) are adapted to VC at boundary of SDH network.

• LX: asynchronous



V5

32 bytes

R R R R R R R RJ2

R R R R R R R R

C1 C2 O O O O R R

32 bytes

R R R R R R R RN2

C1 C2 O O O O R R

32 bytes

R R R R R R R RK4

C1 C2 R R R R R S1S2 D D D D D D D

31 bytes

R R R R R R R R

140octets

11ststfram

efram

e22

ndndframe

frame

33rdrdfram

efram

e44

ththframe

frame

Asynchronous 2048 kbit/s

• Four VC-12 POH bytes(V5, J2, N2 and K4)

• 1023 data bits• Six justification control bits

• C1C1C1=111 ⇒ S1 is a justification bit (data bit)

• C2C2C2=111 ⇒ S2 is a justification bit (data bit)

• Majority vote should be used.• Eight overhead communication channel bits

(0)• 49 fixed stuff bits (R)



Byte Synchronous 2048 kbit/s

• Four VC-12 POH bytes (V5, J2, N2 and K4)

• No justification opportunities• 2 R-bytes per frame

R

R

R

R

R

V5

R500 µs

R

J2

N2

K4

RTime Slot 0

Time Slots 1 to 15Time Slot 16

Time Slots 17 to 31

Time Slot 0Time Slots 1 to 15






140bytes

R Fixed stuff byte

11ststfram

efram

e22

ndndframe

frame

33rdrdfram

efram

e44

ththframe

frame

Documents

SDH Theory