WELCOME TO TRAINING ON PDH &SDH TECHNOLOGY

USEDIN OPTICAL TRANSMISSION

Presented By: A.K. RAI

DM (OPT)

TOPIC COVERED ON SDH

• PDH INTRODUCTION• SDH FUNDAMENTAL• NEXT GEN SDH

Position of Transmission Eqpt. in Telecom NW

Transmission Eqpt.Switching Equpt Switching Equpt

Access NW Access NW

SubscribersSubscribers

TELECOM NETWORK

Different Transmission Media• Twisted pair• Coaxial cable• Wireless transmission.• Optical fiber

Why optical fiber transmission ?

• Large transmission capacity, • Good quality • Small attenuation.• Strict security.• Large trunk distance.

Advantages of Optical Transmission

– Large bandwidth permits high data transmission, which also supports the aggregation of voice, video, and data

– Technological improvements are occurring rapidly, often permitting increased capacity over existing optical fiber

Advantages of Optical Transmission

– Immunity to electromagnetic interference reduces bit error rate and eliminates the need for shielding within or outside a building

– Glass fiber has low attenuation, which permits extended cable transmission distance

Advantages of Optical Transmission

– Light as a transmission medium provides the ability for the use of optical fiber in dangerous environments

– Optical fiber is difficult to tap, thus providing a higher degree of security than possible with copper wire

– Light weight and small diameter of fiber permit high capacity through existing conduits

History of Digital Transmission• ’’70s - introduction of PCM into Telecom 70s - introduction of PCM into Telecom

networksnetworks• 32 PCM streams are Synchronously 32 PCM streams are Synchronously

Multiplexed to Multiplexed to 2.048 Mbit/s (E1)2.048 Mbit/s (E1)• Multiplexing to higher rates via PDHMultiplexing to higher rates via PDH• 1985 Bellcore proposes SONET1985 Bellcore proposes SONET• 1988 SDH standard introduced1988 SDH standard introduced• 1990’s DWDM introduced1990’s DWDM introduced

PULSE CODE MODULATION• The input signal is sampled prior to digitisation and an approximation to

the input is reconstructed by the digital-to-analogue converter:

Sampling Digitisation code, modulate

Transmission•Wire/optical fibre•Aerial/free-space

input

FilteringDigital-to-analogue

conversionDemodulate, Decode

output

Nyquist’s Sampling theorem

For a signal of bandwidth B Hz, the minimum sampling rate is 2B samples/s

• In the telephone system the speech signal has a bandwidth up to 3.4 kHz and a sampling rate of 8 kHz,

The 32-channel PCM Transmission system• 30 speech signals plus two control channels

for signalling and synchronising: – Signal bandwidth 3.4 kHz– Sampling rate 8 kHz (8000samples/sec)

• Hence frame length 1/8000 sec or 125s– Sample size 8 bits/sample

• Hence bit rate from each signal 8*8000=64 kbit/s– 32 channels

• Hence each time slot 3.906 s– 1/(8000*32)

– Overall data rate 2.048 Mbit/s• 32*64 kbit/s =2048 kbit/s or 2.048 Mbit/s

E1 format for 32 CH PCM

• TS 0 is used for synchronization & alarm transport• TS 16 is used for channel associated signalling( CAS)

information & multi frame alignment word (MFA) • 30 Channel for voice

ITU-T G.704 (32 Time Slots)

10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1716 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Omniplexer - 30 Channel Assignments

1- 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16- 17 18 19 20 21 22 23 24 25 26 27 28 29 30

HIGHER ORDER DIGITAL MULTIPLEXING TECHNOLOGY

• Plesiochronous Digital Hierarchy (PDH) • Synchronous Digital Hierarchy (SDH)

PDH MULTIPLEXING

• Plesiochronous means non synchronous.• Multiplexing of 2 Mbit/s to 140 Mbit/s requires two intermediate multiplexing stages of 8 Mbit/s and 34

Mbit/s.• The multiplexing of several tributaries can be achieved by Bit by bit multiplexing (bit interleaving)• There are four bit streams to be multiplexed. One bit is

sequentially taken from each tributary so that the resulting multiplexed bit stream has every fifth bit coming from the same tributary.

PDH features

• Bit interleaving is used for North American and European PDH system. A typical 8.448 Mb/s plesichronous multiplexer has four primary (E1) MUX, each having an out put of 2.048 Mb/s, bit interleaved to form the next level in hierarchy.

• Note that this output rate of 8.448 Mb/s is not exactly four times the tributary bit rate of 2.048Mb/s. This is a result of the non-sychronous nature of the system.

PDH Features

• Every tributary has its own clock. Every tributary is timed with plesiochronous frequency, that is a nominal frequency about which the shifts around it within prefixed limits. For example, the primary multiplexer output is 2.048 Mb/s +- 50ppm.

• To account for the small variations of the tributaries frequencies about the nominal value when multiplexing four tributaries to the next hierarchy level, a process known as positive stuffing (also known as positive justification) is used.

Positive Pulse stuffing or justification

• Pulse stuffing involves intentionally making the output bit rate of a channel higher than the input rate. The output channel therefore contains all the input data plus a variable number of “stuffed bits’ that are not part of the incoming subscriber information.

• The stuffed bits are inserted at the specific locations, to pad the input bit stream to the higher output bit rate. This stuffed bits must be identified at the receiving end so that “de-stuffing” can be done to recover the original bit stream.

Positive Pulse stuffing or justification

• Pulse stuffing is used for higher order multiplexing when each of the incoming lower order tributary signal is unsynchronized, and therefore bears no prefix phase relationship to any of the other.

PDH Multiplexers

Notation Data Rate No. of ch.

E4 139264 Kbps 1920

E3 34368 Kbps 480

E2 8448 Kbps 120

E1 2048 Kbps 30

E0 64 Kbps 1

PDH Bit Rates (European Standard)

Notation Data Rate

T4/DS4 139264 Kbps

T3/DS3 44736 Kbps

T2/DS2 6312 Kbps

T1/DS1 1544 Kbps

T0/DS0 64 Kbps

PDH Bit Rates (American Standard)

PDH Multiplexers

Multiplexer Stages

30 ch2.048 Mb/s

120 ch8.44Mb/s

480 ch34.368

Mb/s

1920 ch139.264

Mb/s

7680 ch564.992Mbit/s

64 kbits/s

x30x4

x4x4

x4

Europe

A typical Plesiochronous Drop and Insert

PDH Equipments in Telecom. Network

2/140 OPTIMUXPDH Equip.

B

2/140 OPTIMUXPDH Equip.

A

2/140 OPTIMUXPDH Equip

B’.

2/140 OPTIMUXPDH Equip.

C

SwitchingEquip.

A

SwitchingEquip.

B

SwitchingEquip.

C

2Mb/s Trib. 1- 64 Add

2Mb/s

1 – 32

Drop

34Mb/s

2Mb/s 1’-32’ Add

2Mb/s 33-64 & 1’-32’ Drop

Tel. Subscribers

Tel. Subscribers Tel. Subscribers

SDH Equipments in Telecom. Network

STM-1/ 4/16Equip. B

STM-1/ 4/16Equip. A

STM-1/ 4/16Equip. C

SwitchingEquip.

A

SwitchingEquip.

B

SwitchingEquip.

C

Tel. Subscribers

Tel. Subscribers

2Mb/s Tribs ADD/DROP

2Mb/s Tribs ADD/DROP 2Mb/s Tribs ADD/DROP

Tel. Subscribers

SDH Equip. in Ring

NMS

Master Clock (2MHz.)

Comparison Of SDH & PDH Technology

For SDH, tributaries & data are mapped/de mapped to VC-4 container directly and have its own identity.

• For PDH , tributaries are mux. /de-mux. in steps and have no identity.

• Synchronous Digital Multiplexers have tributaries with the same clock frequency, and they are all synchronized to a master clock.

• Plesiochronous Digital Multiplexers (non synchronous) have tributaries that have the same nominal frequency (that means there can be small difference from one to another), but they are not synchronized to each other.

• For synchronous case, the pulses in each tributary all rise and fall during the same time interval.

• For the PDH, the rise and fall time of the pulses in each tributaries do not coincide with each other.

Disadvantage of PDH System

• Inability to identify individual channels in a higher-order bit stream;

• Insufficient capacity for network management; • Non compatibility between different vendors.• No worldwide standard optical interface specification.• Restricted to point-to-point transmission.• Can’t sustain high bit rate multiplexing (Above

140Mb/s)• Impossible to extract base-band signal in between

without complete De multiplexing the aggregate• restoration time is several seconds to minutes

Advantage of SDH System• Simple multiplexing processes• Easy access to various signals in a multiplexed high

bit rate signal• Standardized interface can support multi vendor inter

working, international connection and many different services; i.e. Voice , Ethernet, video, ATM, IP

• Support advance Network Management System (OAM&P) – Overhead bits for Fault, Configuration, Performance Monitoring, Security and Accounting management

Advantage of SDH System

• Service restoration time is less than 50 ms• A flexible and efficient way of networking

– Network Distribution: Add/Drop capability– Network survivability: APS (Automatic Protection

Switching)– Traffic Cross connection: capacity management,

bandwidth management and protection route diversity

SDH Frame Format

STM-N

SectionOverhead

MSOHRSOH

AdministrativeUnit

PathOverhead

PointerVirtual

Container

Container

Mapping Elements

• Container• Virtual Container• Tributary Unit• Tributary Unit Group• Administrative Unit• Administrative Unit Group

Mapping Elements

• The Container (C ) Basic packaging unit for tributary signal ( PDH )

Alignment

Clock

Line Input

PDH Circuit

Mapping Elements

• The Virtual Container ( VC ) Formation of the container by adding of a POH ( Path Overhead )

• The Tributary Unit ( TU ) Is formed via adding a pointer to the VC• The Tributary Unit Group ( TUG ) Combines several TUs to formed a new VC

Mapping Elements

• The Administrative Unit ( AU ) Is shaped if a pointer is allocated to the VC formed at last• The Synchronous Transport Module ( STM-N) Formed by adding a section overhead ( SOH ) TO AUs

SDH Hierarchy

STM-16 AU-4-16c C-4-16cVC-4-16c

E1: 2.048Mb/s

E4: 139.264Mb/s

STM-4

STM-1

AU-4-4c

AU-4

AU-3

VC-4-4c

VC-4

C-4-4c

C-4

C-3

C-2

C-12

C-11

VC-3

VC-2

VC-12

VC-11

TUG-3

TUG-2

DS1:1.544Mb/s

E3: 34.368Mb/sDS3: 44.736Mb/s

DS2:6.312 Mb/s

VC-3

TU-3

TU-11

TU-12

TU-2

x4

x3

x1

x7x7

x3x3

564.992Mb/s

2259.968Mb/s

VC-n

AU-n

AUG

STM-n Synchronous Transport Module

Administrative Unit Group: One or more AU(s)

Administrative Unit: VC + pointers

Virtual Container: payload + path overhead

STM-64 AU-4-64c VC-4-64c C-4-64c

AUG

x16

x4

x4x64

x16

x4

9039.872Mb/s

Containers of Base Signal (Low Order Payloads)

High Order Payloads

Frame Structures

*270 Columns

9 Rows

9 Rows

9 Rows

1,080 (270*4 )Columns

4,320 (270*16) Columns

STM-1

155.52 Mbit/s

STM-4

STM-16

622.08 Mbit/s

2488.32 Mbit/s

270 columns x 9 rows = 2430 bytes2430X8byte=19440bits8000 fps x 19440 bits = 155.52 Mbit/s

4 x 155.52 Mbit/s = 622.08 Mbit/s

International organization defined standardized bit rates :

155.520 Mbit/s STM-1 63E1 1890 Ch

622.080 Mbit/s STM-4 252E1 7560 Ch

2.488 Gbit/s STM-16 1008E1 30240Ch

9.953 Gbit/s STM-64 4032E1 120960Ch.

39.81312 Gbit/s STM-256 16128E1 483840Ch

Synchronous Digital Hierarchy (SDH)

Overhead Layer Concepts

path

path termination

pathtermination

service (E1, E4..)mapping demapping

service (E1, E4..)mapping demapping

PTE PTE

multiplex section multiplex section

multipl. section termination

ADMor

DCS

regeneratorsection

regen. section termination

regen. sectiontermination

REG REG

PTE = path terminating elementMUX = terminal multiplexerREG = regeneratorADM = add/drop multiplexerDCS = digital cross-connect system

regen.section

regen.section

regeneratorsection

SDH Frame

SDH Over Head

SDH Overhead

RSOH bytes

• A1, A2 Frame alignment• J0 Reg Trace byte• Z0 Spare byte• B1 Reg Monitoring• E1 Reg EOW• F1 Data Channel• D1-D3 64kbps X 3=192kbps Management

Channel

Regenerator Section– Regeneration section layer is the lowest level of link

components in a SDH network– Deals with the transport of an STM-N frame across

the physical medium– Point-to-point connection between two regeneration

section termination points with direct optical or electrical domain connectivity

– Terminated by Regenerator Section Terminating Equipment (RSTE)

– The Regeneration section is mainly designed to overcome physical limitations of the transport technology

Pointer

• H1, H2, H3 Pointers

– Pointers were included into SDH design to provide tools to compensate for incoming payload phase differences

• It avoids delay and jitter in payload

MSOH

• B2 MSOH error monitoring• K1, K2 APS function• D4-D12 576 data communication channel• S1 syncronization status• M1 MSOH remote monitoring• E2 EOW channel

Multiplex Section– One or more consecutive regenerator sections might

compose a multiplex section• Main element to build different topologies (e.g. ring)

– Deals with the transport of path layer payloads across the physical medium

– Multiplex section is a point-to-point logical link that connects to ADM, MUX, or DCS devices

• These devices might not include a path termination– Overhead is interpreted and modified by Multiplex

Section Terminating Equipment (MSTE)• Multiplex section (MS) overhead is accessed only after the

section overhead has been first terminated

Path Over Head (POH )• J1 trace byte• B3 Error monitoring• C2 Path signal label of container• G1 Higher order alarm status• F2 data channel• H4 pointer indicator• F3 user channel• K3 APS status• N1 TCM byte

Path Over Head (POH )• J1 trace byte• B3 Error monitoring• C2 Path signal label of container• G1 Higher order alarm status• F2 data channel• H4 pointer indicator• F3 user channel• K3 APS status• N1 TCM byte

POH– One or more connected multiplex sections may provide

a transport service for a path• Multiplex section may carry multiple paths by multiplexing

– Deals with the transport of various payloads between SDH terminal multiplexing equipment

– Path layer maps payloads into the format required by the MS Layer

– Communicates end-to-end via the Path Overhead (POH)

– POH is terminated and modified by Path Terminating Equipment (PTE)

• Regenerator and multiplex section overhead must be terminated to access the overhead

SDH TOPOLOGY• Point-to-point

– Used for SDH island trunks in old asynchronous networks, or data services as POS or ATM links

– Linear point-to-multipoint• Adds up ADM in the middle• Max. 16 nodes

– Hub network• A DCS interconnects ADMs

– Ring• ADMs are put into a ring• Redundant, multiple connected rings

– Automatic protection switching (APS)

USHR

Add and Drop Example– STM-4 Ring– 4 x STM-1 channels– Uni-directional routing– Provisioning:

• add 1-3 (drop 3-1)• add 3-4 (drop 4-3)• add 4-2 (drop 2-4)

– 2 channels occupiedADM

2

ADM3

ADM1

ADM4

OC-12

Drop

Add 1-3

Add 3-4

Drop

Add 4-2

Drop

• Network Protection

1:1 protection

– 1:1 protection (special case of 1:n)• Bi- or unidirectional• Revertive• Typically dedicated protection• May transmit traffic on both channels, or use protect for

low priority traffic

Protection facility

Working facility

ADM/Router ADM/Router

1:n protection

– 1:n protection• Bi- or unidirectional• Revertive• Shared protection facility

Protection facilityADM/Router ADM/Router

A

CE

BF

D

Loops

Fiber cut

WorkingTraffic

STM-1#10 into STM-1#4

STM-1#10 into STM-1#4

STM-1#4 into STM-1#10

•No dedicated protection bandwidth - only used when protection required•Only nodes next to the failure know

about the protection switch•No traffic lost

Shared protection

*

Next Generation SDHNext Generation SDHTechnologyTechnology

SDH/SONET/OTN

SDH

MU

X/D

EM

UX

Nat

ive

Inte

rfac

es

New SDH

?VCVirtual

Concatenation

LCASLink

Capacity Adjustment

Scheme

GFPGeneric Frame

Procedure

Ethernet

Ficon

Escon

Fibre Channel

Edge CoreAdaptation

Customer Operator

GFP

GFP - Client Specific Aspects (payload dependent)

GFP - Common Aspects (payload independent)

SDH/SONET VC-n Path

OTN ODUk Path

Others(e.g. Fibre)

Ethernet IP/PPP Fibre Channel OthersClients

GFP

Transport

Frame Mapped Transparent Mapped

ESCON

Making SDH efficient through Virtual Concatenation (VC)

VC- 3VC- 3

VC- 4

VC-4-4cVC-4-4c

VC-4-16cVC-4-16c

SDH

92%98%

100%100%100%100%89%95%

EthernetATM

ESCON

Fibre Channel

Fast Ethernet

Gigabit Ethernet

data

10 Mbit/s25 Mbit/s

200 Mbit/s400 Mbit/s800 Mbit/s

100 Mbit/s

1 Gbit/s

efficiency

100M Ethernet STM-1= 64 x VC-12

VC-12-5v

VC-12-46v

2x 10M Ethernet VC-12-5v

8x E1 Services

Example:

More services integrated- by using VC!

VC-12-5vVC-12-12vVC-12-46v

VC-3-2vVC-3-4vVC-3-8vVC-4-6vVC-4-7v

NewSDH

20%50%

66%

33%66%26%42%

efficiency

SDH Line Rates

10 M

Transport 10M Ethernet over SDH?

C-4-4c 0.599 Gbit/sC-4-16c 2.396 Gbit/sC-4-64c 9.584 Gbit/sC-4-256c 38.338 Gbit/s

Contiguous ConcatenationContiguous Concatenationonly large containers!

C-11 1.600 Mbit/sC-12 2.176 Mbit/sC-2 6.784 Mbit/sC-3 48.384 Mbit/sC-4 149.760 Mbit/s

SDH Payload Sizes

Standard Containers are inefficient!

Concatenate 5 x VC-12!

!5x

Contiguous Concatenation

Offers concatenated payloads in fixed, large steps

One towing truck (POH) for all containers

All containers are on one path thru the network

VC-4-4c

C4 C4 C4 C4

Virtual Concatenation

Offers structures in a fine granularity Every container has its own towing truck

(POH) Every container might take a different

path

VC-4-4v

VC-4 #1VC-4 #2VC-4 #3VC-4 #4

AU-4 Pointers

MSOH

RSOH

VC-4-5 VC-4-6 VC-4-7 VC-4-8

VC-4-9 VC-4-10 VC-4-11 VC-4-12

VC-4-13 VC-4-14 VC-4-15 VC-4-16

VC-4-1 VC-4-2 VC-4-3 VC-4-4STM-16

ContiguousConcatenation

VC-4-4c

AU-4 Pointers

MSOH

RSOH VC-4-1 VC-4-2 VC-4-3 VC-4-4

VC-4-5 VC-4-6 VC-4-7 VC-4-8

VC-4-9 VC-4-10 VC-4-11 VC-4-12

VC-4-13 VC-4-14 VC-4-15 VC-4-16

The block has to start at defined positions in the payloadThe block consists of consecutive VC-4-nsThere is only one pointer

STM-16

VirtualConcatenation

VC-4-7v

AU-4 Pointers

MSOH

RSOH

VC-4-5 VC-4-6 VC-4-7 VC-4-8

VC-4-9 VC-4-10 VC-4-11 VC-4-12

VC-4-13 VC-4-14 VC-4-15 VC-4-16

VC-4-1 VC-4-2 VC-4-3 VC-4-4

Pointers

MSOH

RSOH VC-4-1 VC-4-2 VC-4-3 VC-4-4

VC-4-5 VC-4-6 VC-4-7 VC-4-8

VC-4-9 VC-4-10 VC-4-11 VC-4-12

VC-4-13 VC-4-14 VC-4-15 VC-4-16

The blocks can start at any position in the payloadThe block consists of distributed VC-nsEach container has it‘s own pointer

VCG Granularity

VCG Payload Capacity

Maximum

MinimumVCGs:VC-4-1v Payload Size 149,76 Mbit/sVC-4-2v Payload Size 299,52 Mbit/s

VC-4Example High Order VC:VC-4 Container Size 150,3 Mbit/sVC-4 Payload Size 149,76 Mbit/s

VC-4-7v Payload Size 1048,3 Mbit/s

VC-4-256v Payload Size 38338 Mbit/s

Minimum

VCG GranularityVCGs:VC-12-1v Payload Size 2,176 Mbit/sVC-12-2v Payload Size 4,352 Mbit/s

VCG Payload Capacity

Maximum

Example Low Order VC:VC-12 Container Size 2,240 Mbit/sVC-12 Payload Size 2,176 Mbit/s

VC-12-5v Payload Size 10,88 Mbit/s

VC-12-64v Payload Size 139,26 Mbit/s

VC-12

The end