Introduction To Transmission - · PDF filePDH Plesiochronous Digital Hierarchy ... The Synchronous Digital Hierarchy. SDH – Global Networks European bit rates 64Kb/s (PCM) x32 2Mb/s

Introduction To Transmission

Introduction

Telecommunications –

Communication over distance

Transmission networks deal with getting information from one location to another.

Transmission Technologies

FDM – Frequency division multiplexing.

TDM – Time Division Multiplexing.

DWDM – Dense Wave Division Multiplexing

Time Division Multiplexing

1 1 1 1 1 1 1 1

2 2 2 2 2 2 2 2

3 3 3 3 3 3 3 3

4 4 4 4 4 4 4 4

4 3 2 1 4 3 2 1

Low order signals

Higher order signal

Dense Wave Division Multiplexing

OneWavelength

( λ )



DWDM Signal

λ1λ2λ3λ4

λ5λ6λ7λ8

λ1λ2λ3λ4

λ5λ6λ7λ8

Primary Rate Multiplexing

Sampling Quantising Encoding

Multiplexing

Analogue Signal

PCM Signal


Analogue signal

Sampled at 8000 Hz


Quantising

Encoding10110010110010010101010


0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031

2MBit/s

64KBit/s

0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031

31 Channels

Framing

0 1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031

15 Channels 15 Channels

Framing Signalling

31 C

han

nel

30 C

han

nel

PDH

Plesiochronous Digital HierarchyPlesiochronous – “Almost Synchronous”

Multiplexing of 2Mbit/s signals into higher order multiplexed signals.

Laying cable between switch sites is very expensive.

Increasing traffic capacity of a cable by increasing bit rate.

4 lower order signals multiplexed into single higher order signal at each level.

PDH

28

834

34140

140565 565140

14034

348

82

PDH

234

34140

140565 565140

14034

342

PDH LimitationsSynchronisation

TX RX

1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0

The data is transmitted at regular intervals. With timing derived from the transmitters oscillator.

The data is sampled at the same rate as it is being transmitted.


TX RX

1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0


The data is sampled at a slower rate than the transmitter.

These bits are missed at the receiver end.


TX RX

1 1 1 1 1 1 1 1

0 0 0 0 0 0 0 0


The data is sampled at a faster rate than the transmitter.

These bits are sampled twice at the receiver end.


TX

RX

RX

TX

DEMUX

MUX

MUX

DEMUX

HOTX

HOTX

HORX

HORX

Timingextraction

Timingextraction


bit rateadaption

bit rateadaption

4 3 2 1

3 2 1

‘fast’ incoming2Mbit/s channel

‘slow’ incoming2Mbit/s channel

J J J 3 2 1

J J 4 3 2 1

Justificationbits

Justificationbits

Masteroscillator

8Mbit/s

PDH LimitationsMux Mountain

28

834

34140

140565565140

14034

348

82

Add / Drop

Increased equipment requirementsIncreased space on site.Increased spares requirements.

PDH LimitationsLack Of Traffic Resilience

140565 565140

Traffic LostTraffic Lost

PDH LimitationsLimited Network Management

140565 565140

Traffic LostTraffic Lost

DCN DCN

! Alarm reported. No diagnosis tools available.Maintenance staff sent to site.

PDH LimitationsNo Mid-Fibre Meet

140565 565140

Vendor A Vendor B

SDH

The Synchronous Digital Hierarchy

SDH – Global Networks

European bit rates

64Kb/s(PCM)

x322Mb/s

x48Mb/s

x434Mb/s

x4140Mb/s

x4565Mb/s

North American bit rates

1.5Mb/sx24

6Mb/sx4

45Mb/sx7

XNot supported in SDH.

Non standardX

1st Order 2nd Order 3rd Order 4th Order

E1 E2 E3 E4

DS1 DS2 DS3

SDH – Network TopologiesLine Systems

Terminal Terminal

SDH – Network TopologiesLine Systems

Terminal TerminalRegenerator

SDH – Network TopologiesRing Systems

ADM ADM

ADM

ADM

STM-1

Pointers

Overheads

Overheads

Payload

STM-1

Pointers

Overheads

Overheads

Payload

9 Bytes

9 Bytes

261 Bytes

270 Bytes

STM-1

Pointers

Overheads

Overheads

Payload

9 Bytes

9 Bytes

261 Bytes

270 Bytes

1 2 3 4 5 6 7 8 9 10

11 12

268

269

270

2161

2162

2163

2164

2165

2166

2167

2168

2169

2170

2171

2172

2428

2429

2430

271541

811

10

811

351

16

211

891

Transmission time - 125 µseconds

STM-1 Overheads

Repeater Section Overheads

Multiplex Section Overheads

AU Pointers

3 Bytes

1 Byte

5 Bytes

9 Bytes

STM-1 Overheads

ADM Regen Regen ADMSDH SDH SDHSDH SDH

STM-1 Overheads


RS RS RS

STM-1 Overheads


MS

STM-1 Overheads


POH

STM-1 Overheads


POH

RS RS RS

MS

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0 X X

B1 MD MD E1 MD F1 X X

D1 MD MD D2 MD D3


AU Pointers

X – Reserved bytes

MD – Media dependent

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The A1 & A2 bytes are used for frame

alignment.

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The J0 byte is used to carry the RS Path Trace. This is a

repetitively transmitted string used to identify the transmitting node.

SDH Path Trace

ADM ADM

SDHSDH SDHSDH

London Paris

“London” “Paris”

SDH Path Trace

ADM ADM

SDHSDH SDHSDH

London Paris


“Paris” “London”

SDH Path Trace

ADM ADM

SDHSDH SDHSDH

London Paris




SDH Path Trace

ADM ADM

SDHSDH SDHSDH

London Paris

!!



“Amsterdam” “London”X

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The B1 byte is used for parity error checking. It carries the parity of the complete previous

frame.

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The E1 byte provides a 64Kbit/s channel that can be used to carry

voice for engineering order wire use. As this is in the RS overhead this channel can be

accessed at any node.

SDH EOW


STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The F1 byte is reserved for user purposes.

STM-1 RS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3


AU Pointers

The D1, D2, & D3 bytes provides a

192Kbit/s channel that is used as a data communications channel between

nodes for management purposes.

SDH Management


Network Management Centre

DCN Network

DCC Channels

DCC Channels

DCC Channels

DCN Connection

DCN Connection

GatewayNode

GatewayNode

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

X – Reserved bytes

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The B2 byte allows for parity error checking within the MS overhead. Parity is computed from the previous frame with the exception of the RS overheads.

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The K1 & K2 bytes are for used for automatic protection switching. The are used to control the switches that occur on the network.

SDH Network Resilience

ADM

ADM

ADM ADM

Active path

Standby path


ADM

ADM

ADM ADM

Active path

Standby path


ADM

ADM

ADM ADM

Active path

Standby path

Network ManagementCentre

Switch

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The Dx bytes are for used for a DCC channel within the MS overhead.576Kbit/s are available for communication within this channel.

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The S1 byte is used for synchronisation messaging. It denotes the quality level of the synchronisation that can be derived from this incoming signal.

SDH Network Synchronisation

Primaryreference

Secondaryreference

ADM

ADM

ADM ADM


Primaryreference

Secondaryreference

ADM

ADM

ADM ADM


Primaryreference

Secondaryreference

ADM

ADM

ADM ADM

!!


Primaryreference

Secondaryreference

ADM

ADM

ADM ADM!

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The Z1 and Z2 bytes currently have no allocated function.

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The M1 byte is used as a remote error indicator.

Remote Error Indication


B2 error detected

Multiplex section

Multiplex section

Remote Error Indication


B2 error detected

MS-REI received

MS-REI generated

Multiplex section

Multiplex section

STM-1 MS Overheads

A1 A1 A1 A2 A2 A2 J0

B1 E1 F1

D1 D2 D3

B2 B2 B2 K1 K2

D4 D5 D6

D7 D8 D9

D10 D11 D12

S1 Z1 Z1 Z2 Z2 M1 E2 X X


AU Pointers

The E2 byte provides an EOW channel within the MS overhead.

SDH Pointers


AU Pointers


SDH Pointers


AU Pointers



AU Pointers


Payload area

Payload area

Actual Payload

SDH Pointers


AU Pointers



AU Pointers


Payload area

Payload area

Actual Payload

SDH Pointers


AU Pointers



AU Pointers


Payload area

Payload area

Actual Payload

SDH Pointers


AU Pointers



AU Pointers


Payload area

Payload area

Actual Payload

SDH Pointers

H1 H1 H1 H2 H2 H2 H3 H3 H3

9 Bytes

SDH Pointers

H1 H1 H1 H2 H2 H2 H3 H3 H3

1 0 0 1 S S 1 1 1 0 0 1 S S 1 1

SDH Pointers

H1 H1 H1 H2 H2 H2 H3 H3 H3

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

SDH Pointers

H1 H1 H1 H2 H2 H2 H3 H3 H3

NDF NDF NDF NDF S S I D I D I D I D I D

Pointer value

SDH Pointers

H1 H1 H1 H2 H2 H2 H3 H3 H3

Payload

Past STM-1

Pointers

Overheads

Overheads

Payload

144 Bytes 4176 Bytes

4320 Bytes

9 Bytes

STM16 Frame

Past STM-1

Optical

Optical

Optical

Optical

Electrical / Optical

Electrical

Electrical

Electrical

Medium

40Gbit/sSTM-256 (future)

10Gbit/sSTM-64

2.5Gbit/sSTM-16

622Mbit/sSTM-4

155Mbit/sSTM-1

140Mit/sE4

34Mit/sE3

2Mit/sE1

Bit rateSignal

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

Mapping

Aligning

Multiplexing

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x7

x3

x3

xN

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

C-3AU-3

C-2

C-12

C-11

x3The Container is the basic element of SDH. Payload signals that are to be transported across the SDH layer are mapped into the appropriate container.

1.5M maps into a C-112M maps into a C-126M maps into a C-234M maps into a C-345M maps into a C-3140M maps into a C-4

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11

VC-12

VC-2

VC-3

x3

Overhead bytes collectively known as the Lower Order Path Overhead are added to the container to form a Virtual Container.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11

VC-12

VC-2

VC-3

x3 The VC-11/12/2 POH is

comprised of :

V5 - Indication and error monitoring. J2 - Path indicationN2 - Tandem connection monitoringK4 - Automatic protection switching

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11

VC-12

VC-2

VC-3

x3

The VC-3/4 POH is comprised of :

J1 - Path indication B3 - Quality monitoringC2 - Container formatG1 - Transmission error acknowledgmentF2 - MaintenanceH4 - Superframe indicationF3 - MaintenanceK3 - Automatic protection switchingN1 - Tandem connection monitoring

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

x3A Pointer is added to the Virtual Container to create a

Tributary Unit.

This pointer functions in the same way as the pointer

within the section overheads but is applied at a lower level and should not be confused with the higher level pointer.

This lower level pointer is known as the TU Pointer

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

x4

x3

Four of the TU-11 Tributary Units can be multiplexed

together to create A Tributary Unit Group-2 (TUG-2)

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

x4

x3

x3

Alternatively three of the TU-12s can be multiplexed together to form the TUG-2

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

x4

x3

x1

x3

Or the last way to construct the TUG-2 is to use a single

TU-2.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

TUG-3

x4

x3

x1

x7

x3

In a typical lower order SDH network carrying 2M traffic 7 TUG-2s will be multiplexed together to create a TUG-3.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

TUG-3

x4

x3

x1

x1

x7

x3

Alternatively if the network is carrying 34M or 45m traffic the TUG-3 can be created from a

single TU-3

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

TUG-3

x4

x3

x1

x1

x7

x3

x3

3 TUG-3s can be multiplexed together to create a VC-4.

When this is created another layer of path overhead is

added. This is known as the High Order Path Overhead.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

TUG-3

x4

x3

x1

x1

x7

x3

x3

A single VC-4 will have a pointer added to create an

Administrative Unit, known as an AU-4

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x3

x3

The Administrative Unit Group is created when

multiplexing several Administrative Units.

Using this route through the hierarchy only one AU-4 is

needed to create the AUG, no processing is performed or

overhead added.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x3

x3

xN

To create the SDH signal several AUGs are multiplexed

together with the section overheads added to create the

STM-N signal.

For example, one AUG would be used in an STM-1, whereas sixteen AUGs would be used to create an STM-16 signal

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x3

xN

There is an alternative way to create the signal, although the

one shown here is typically used. The alternative route is

mainly used when interconnecting with SONET networks or for SDH radio

applications where lower bit rate STM-0 / OC-1s are used as the building block instead

of STM-1

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x7

x3

xN

Seven TUG-2s are multiplexed together to form a VC-3. This stage also adds a High Order

Path Overhead.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x7

x3

xN

A pointer is added to the VC-3 to create an AU-3. This pointer

is know as an AU Pointer.

SDH Hierarchy

C-4 140M

45M34M

6M

2M

1.5M

VC-3 C-3

VC-4

AU-3

AU-4

C-2

C-12

C-11VC-11TU-11

VC-12TU-12

VC-2TU-2

VC-3TU-3

STM-N

TUG-2

TUG-3

AUG

x4

x3

x1

x1

x7

x7

x3

x3

xN

Three AU-3s can be multiplexed together to form

an AUG if an STM-1 or higher is going to be created.

The AUG then has the section overheads added.

DWDM Within The Network

ADM

ADM

ADM ADM

Site D

Site C

Site A

Site

B


Site DS

ite C

Site A

Network1

Site F

Site ENetwork

2

ADM

ADM

ADM

ADMADM

ADMADM

Site

B

ADM


Site D

Site CSite A

Network1

Site F

Site E

Network2

Site B

ADM ADM

ADM

ADM

ADM ADM

ADM

ADM

Protocol Independent

DWDM networks are protocol independent.

They transport wavelengths of light and do not operate at the protocol layer.

SDHSONETEthernetDigital Video….

DWDM Amplifiers

Red A

mp

lifier

λ1λ2λ3λ4

λ5λ6λ7λ8

λ1λ2λ3λ4

λ5λ6λ7λ8

DW

DM

Co

uple

r

Blue

Am

plifier

DW

DM

Co

upler

Blue

Am

plifier

Red A

mp

lifier

Blue direction

Red direction

DWDM Equalisation

This wavelength has not been equalised

DWDM EqualisationR

ed Am

plifier

λ1

λ2

λ3

λ4

λ5

λ6

λ7

λ8

DW

DM

Co

uple

r

AD

M

High

Order

Low O

rder

TX

TX

RX

RX

Fib

re Ma

nage

ment F

ram

e

Electrica

l/Fibre M

an

agem

ent Fra

me

AD

M

High

Order

Low O

rder

TX

TX

RX

RX

Fib

re Ma

nage

ment F

ram

e

Electrica

l/Fibre M

an

agem

ent Fra

me

Fibre M

ana

gem

ent F

ram

e

Variable Optical

Attenuator

Variable Output Transmitter

Optical Dispersion

Chromatic Dispersion

Polarisation Mode Dispersion

While a light pulse is not itself polarised, it consists of two perpendicularly polarised components.

Polarisation Mode Dispersion

An imperfectly shaped core can affect one of the components of the pulse

Impurities within the core can delay the arrival of one of the components.

Four Wave Mixing

195.975 196 196.025 196.05 196.075 196.1 196.125 196.15 196.175

Frequency (THz)

Po

wer

With two wavelength within the fibre, two additional wavelengths are generated.

f(123)= f1+f2-f3

DWDM channel1528.77nm

( f1 )

DWDM channel1529.16nm

( f2 )f221 f112

Four Wave Mixing

195.9 195.9 195.9 196 196 196 196 196.1 196.1 196.1 196.1 196.2 196.2 196.2 196.2

Frequency (THz)

Po

wer DWDM Channels

FWM Channels

DWDMchannel

1528.77nm( f3 )

DWDMchannel

1529.16nm( f2 )

DWDMchannel

1529.55nm( f1 )

f321

f331

f332f331,f231

f132

f312

f223 f112

f123

f213

f113

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Introduction To Transmission - · PDF filePDH Plesiochronous Digital Hierarchy ... The Synchronous Digital Hierarchy. SDH – Global Networks European bit rates 64Kb/s (PCM) x32 2Mb/s