pdh-amp-sdh

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Introduction to Introduction to PDH & SDHPDH & SDH

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• Transmitter, Medium, Receiver

• Network

• Communication Rules – Protocol

Communication Basics

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• Copper - Electrical

• Wireless - Microwave / Radio

• Fiber - Optical

• Satellite

Medium

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Transmission Types

• Asynchronous

• Plesiochronous

• Synchronous

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PDH PDH Plesiochronous Plesiochronous

Digital HierarchyDigital Hierarchy

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If two digital signals are plesiochoronous then their transitions occur at “ almost” the same rate, with any variation being constrained within tight limits. Although this clocks are extremely accurate, there is a difference between one clock and the other.

Plesiochoronous Signal

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565 Mbit/s

Drop & Add

The PDH Multiplexing140 Mbit/s

34 Mbit/s

565Mbit/s

8 Mbit/s

2 Mbit/s

140-

565

MU

X &

LTE

140-

565

MU

X &

LTE

34-1

40 M

UX

34-1

40 M

UX

8-34

MU

X

8-34

MU

X

2-8

MU

X

2-8

MU

X

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Limitation of the PDH Network

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

• Insufficient capacity for network management.

• Most PDH network management is proprietary.

• There is no definition of bit rates greater than 140 Mbit/s

• There are different hierarchies in use around the world.

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Synchronous Digital

Hierarchy

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The Synchronous Digital Hierarchy (SDH)

• Need for extensive network management capability within the hierarchy.

• Standard interfaces between equipment.

• Need for inter-working between north American and European systems.

• Facilities to add or drop tributaries directly from a high speed signal.

• Standardization of equipment management process.

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HistoryHistoryPDH Transmission Rates

Hierarchical Level

American DS-x

European CEPT-x

JapaneseInter-

national

0

2

3

4

1

64 64 64 64

84486312

1544 204820481544

63126312

97728139264139264 139264

44736 4473634368 32064

GTL LimitedCOMPARISION OF SDH / PDHPDH SDH

The reference clock is not synchronized

throughout the network

The reference clock is synchronized

throughout the network.

Multiplexing / Demultiplexing

operations have to be performed from

one level to the next level step by step.

The synchronous multiplexing results in

simple access to SDH system has

consistent frame structures throughout

the hierarchy.

The payload is not transparent. The payload is transparent

PDH system has different frame

structures at different hierarchy levels.

SDH system has consistent frame

structures throughout the hierarchy.

Physical cross-connections on the same

level on DDF are forced if any

Digital cross- connections are provided

at different signal levels and in different

ways on NMS

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PDH SDH

G.702 specifies maximum 45Mpbs &

140Mpbs & no higher order (faster)

signal structure is not specified

G.707 specified the first level of

SDH.That is, STM-1, Synchronous

Transport Module 1st Order & higher.

(STM-1,STM-4,STM-16, STM-64)

PDH system does not bear capacity to

transport B-ISDN signals.

SDH network is designed to be a

transport medium for B-ISDN, namely

ATM structured signal.

Few services are available It will transport variety of services.

Limited amount of extra capacity for

user / management

It will transport service bandwidths

Sufficient number of OHBs is available

Bit - by - bit stuff multiplexing Byte interleaved synchronous

multiplexing.

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STM-N Frame FormatSTM-N Frame Format

• STM - "Synchronous Transport / Transmission Module"

• STM-N general format

• Basic frame STM-1 consists of • 270 x 9 = 2430 octets • 9 x 9 = 81 octets section overhead • 2349 octets payload

• Higher rate frames are derived from multiples of STM-1 according to value of N

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Elements of SDH Container (C) Virtual Container (VC)

Tributary Unit (TU)

Tributary Unit Group (TUG)

Administrative Unit (AU)

Administrative Unit Group (AUG)

Synchronous Transport Module - N (STM – N)

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SDH Generalised Multiplexing Structure

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• Input signals are placed into the containers

• It adds stuffing bytes for PDH signals,which compensates for the permitted frequency deviation between the SDH system and the PDH signal

• C12 (2 Mbps – G.703)• C11 (1.5 Mbps)• C2 (6 Mbps)• C3 (34 / 45 Mbps)• C4 (140 Mbps)

Container

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Container

ALIGNMENT : It is a process of adopting the incoming PDH signals into containers i.e. PCM 30 or 2Mbps to C12.

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Mapping is a process used when tributaries are adapted into VCs by adding justification bits and Path overhead information

The 2 Mbps signals are not synchronized to the SDH signal.It imposes no signal structure requirements, so 2 Mbps signals using this mapping do not need to be framed.This allows easy interface with existing PDH systems as variable bit justification occurs as part of this type of 2Mbps mapping.

Mapping (Asynchronous)

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• It adds overheads to a container or groups of tributary units, that provides facilities for supervision and maintenance of the end to end paths• VCs carry information end to end between two path access points through the SDH system• VCs are designed for transport and switching sub-SDH payloads

• VC12 (C12 + POH)• VC11 (C11 + POH)• VC2 (C2 + POH)• VC3 (C3 + POH)• VC4 (C4 + POH)

Virtual Container

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Virtual Container

• The AU pointer locates a higher-order VC, and the TU pointer locates a lower-order VC. For example, an AU–3 contains a VC–3 plus a pointer, and a TU–2 contains a VC–2 plus a pointer.

• A VC is the payload entity that travels across the network, being created and dismantled at or near the service termination point.

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• It adds pointers to the VCs

• This pointer permits the SDH system to compensate for phase differences within the SDH network and also for the frequency deviations between the SDH networks

• TUs acts as a bridge between the lower order path layer and higher order path layer

• TU12 (VC12 + pointer)• TU2 (VC2 + pointer) • TU3 (VC3 + pointer)

Tributary Unit

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• It defines a group of tributary units that are multiplexed together

• As a result, a TU group could contain one of the following combinations

• Three TU-12s (TUG – 2)

• Seven TUG-2s (TUG – 3)

Tributary Unit Group

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It adds pointer to the HO Virtual containers (similar to the tributary unit) • AU - 3 (VC-3 + pointer)• AU - 4 (VC-4 + pointer)

Administrative Unit Group

• It defines a group of administrative units that are multiplexed together to form higher order STM signal

Administrative Unit

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Synchronous Transport Module – n

• It adds section overhead (RSOH & MSOH) to a number of AUGs that adds facilities for supervision &maintenance of the multiplexer & regenerator sections

• This is the signal that is transmitted on the SDH line

• The digit “n” defines the order of the STM signal

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STM-1 Frame StructureSTM-1 Frame Structure

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• As indicated, the STM – n signal is multiples of frames

consisting of 9 rows with 270 bytes in each row• The order of transmission of information is first from

left to right and then from top to bottom• The first 9 bytes in each row are for information and

used by the SDH system itself.This area is divided into 3 partso Regenerator Section Overhead(RSOH)o Multiplex Section Overhead(MSOH)o Pointers

STM-1 Frame StructureSTM-1 Frame Structure

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Mapping of 2Mbps into STM – N signal

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• Stuffing bytes are added in the container one at the head and the other at the tail of each frame• The lower order POHs are added at the head of each frame in the VC12• Adding of pointers takes place at the head of each frame in the TU12• Three parallel TU12s are multiplexed to form a TUG-2• Seven TUG-2s are multiplexed to form a TUG-3• Multiplexing of three TUG3s with stuffing bytes at the header forms the input to VC4

Mapping of 2Mbps into STM – N signal

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• Higher order path over heads are added at this level, which is the input to AU4• The location of the starting byte J1(VC-4) is written in pointer bytes H1 and H2. This process is defined as pointer processing• AUG, performs the function of concatenation in case of higher order STMs• In STM-1,virtually there is no difference between AUG and AU-4

Mapping of 2Mbps into STM – N signal

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2.048 Mbps(E1)

1 2 3 32

32 Bytes

1 2 3 32VC-1235 Bytes

POH (Lower Order)

1 2 3 32C-1234 Bytes

Stuffing Bytes

Mapping of 2Mbps into STM – N signal

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TU-12

36 Bytes

Pointer

9 Rows

4 Columns

TU 12 is arranged Into Matrix of 9 X 4

Mapping of 2Mbps into STM – N signal

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TUG-2 9 Rows

12 Columns

9 Rows

4 Columns 4 Columns 4 Columns

TU-12 TU-12 TU-12

Multiplexing

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7 TUG-2s

Stuffing Bytes

86 Columns 84 Columns

TUG 3

X 7 TUG-2 TUG-3(Multiplexing)

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HOPOHVC - 4

258 Columns

Stuffing Bytes

261 Columns

TUG - 3 TUG - 3 TUG - 3

86 Columns

X 3 TUG–3

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261 Columns

AU – 4 (Adding Pointer)

PO

H

Pay LoadAU Pointer

9 Columns

4 th Row

Pay LoadPO

H

VC - 4

261 Columns

9 rows

Mapping of 2Mbps into STM – N signal

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PAY LOAD

RSOH

MSOH

AU Pointer

261 Columns

270 Columns

9 Columns

1-3 rows

5-9 rows

4th row

STM-1 Frame Structure

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SDH Over HeadsSDH Over Heads

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STM-1 Section OverheadSTM-1 Section Overhead

Y Y 1 1

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A1 & A2 – Framing Bytes

• These two bytes indicate the beginning of the STM-N frame

J0 – Regenerator Section Trace

• It’s used to transmit a Section Access Point Identifier so that a section receiver can verify its continued connection to the intended transmitter• Identifies by a number in the individual STM – 1s of a higher order STM - n

Regenerator Section Overhead

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• This is a parity code (even parity), used to check for transmission errors over a regenerator section

• Its value is calculated over all bits of the previous STM-N frame after scrambling, then placed in the B1 byte of STM-1 before scrambling

E1 – Engineering Order wire • This byte is allocated to be used as a local order wire channel for voice communication between regenerators

• This byte functionality is available at both multiplexers and Regenerators

B1- Bit Interleaved parity (BIP-8)

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Bit Interleaved parity (BIP)• Each bit in BIP will indicate the parity of all respective

bits in the previous frame.

•Regenerator section BIP is calculated over the entire signal including all RSOH,MSOH,VC-4 POH and payload of the previous frame..The result is placed in B1 for a STM-1.

• MS BIPs are calculated over the previous STM-1 frame,minus RSOH, and placed in the B2 bytes.

• Path BIP’ are calculated over the previous frame, minus RSOH and MSOH and are found in the B3 byte of every STM-1.

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F1 – User Channel

• This byte is set aside for the user’s purposes

D1 to D3 – Data Communication Channel • These three bytes form a 192 kbps DCC for Operation & management of the SDH System

• Network management system sends / receives provisioning, security, status / control alarm and performance monitoring command / response by way of DCC

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• This is used to determine if a transmission error has occurred over a multiplex section. It is even parity, and is calculated over all bits of the MS Overhead and the STM-N frame (except the regenerator section) of the previous STM-N frame before scrambling

• The value is placed in the three B2 bytes of the MS Overhead before scrambling. These bytes are provided for all STM-1 signals in an STM-N signal

B2 – Bit Interleaved parity (BIP – 24)

Multiplex Section Overhead

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D4 to D12 – Data Communication Channel• These nine bytes form a 576 kbps DCC for Operation & management of the multiplexers on a SDH line

• Network management system sends / receives provisioning, security, status / control alarm and performance monitoring command / response by way of DCC

K1 & K2 – Multiplex Section Protection

• These two bytes are used for MSP signaling between multiplex level entities for bi-directional automatic protection switching and for communicating Alarm Indication Signal (AIS) and Remote Defect Indication (RDI) conditions

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Automatic Protection Switching•APS is the capability of a transmission system to detect a

failure on a working facility and to switch to a standby facility to recover the traffic.

•Only the Multiplex Section in SDH is protected in this automatic fashion.

•MS protection mechanism is coordinated by K1 and K2 bytes.

•Path protection is managed at a higher level by network management functions

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Protection Switching is initiated due to :

• Signal failure

• Signal degradation

• In response to commands from a local craft terminal or a remote network manager.

Two modes of APS are provided

• 1+1 Protection

• 1:N protection

Automatic Protection Switching

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E2 – Engineering Order wire

• This byte is allocated to be used as a local order wire channel for voice communication between multiplexers• This byte is not accessible at the regenerators

M1 - Remote Error indication

• It is used to indicate the MS layer remote error indication (MS-REI)

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S1 Synchronization status message byte (SSMB)

• Bits 5 to 8 of this S1 byte are used to carry the synchronization messages

0000 Quality unknown (existing sync. network)

0010 G.811 PRC (Primary Reference Clock)

0100 G.812 transit SSU-A (Synchronisation Supply Unit - A)

1000 G.812 local SSU-B (Synchronisation Supply Unit – B)

1011 G.813 Option 1 SEC (Synchronous Equipment Timing Clock)

1111 Do not use for synchronization. This message may be emulated by equipment failures and will be emulated by Multiplex Section AIS signal.

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H1 Y Y H2 1 1 H3 H3 H3

H1 & H2 = VC payload pointer

H3 = Negative Justification

1 = All 1’s

Y = 1001SS11 (S bits unspecified)

SDH Pointers Use of Pointers• It indicates the starting position of VC• It is also used for justification• AU pointer is also used for concatenation

• SDH provides payload pointers to permit differences in the phase

and frequency of the Virtual Containers (VC-n) with respect to the

STM-N frame

• Lower-order pointers are also provided to permit phase differences

between VC-12/VC-2 and the higher-order VC-3/VC-4

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Path OverHead

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J1- Path trace

• Starting point of VC• It is used to transmit repetitively a path access point identifier, similar to J0

B3 – Path Bit Interleaved Parity – BIP- 8

• Error Monitoring over the previous VC-4 frame.• Even parity is used to monitor path errors

Path Overhead

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C2 – Signal Label• It is defined to indicate the composition or the maintenance of the VC-4

G1- Path status• It is defined to send back the path status and performance to where the path is generated

F2,F3 – Path User Channels• It is assigned for user communication purposes between path elements by the network operator

H4 – Multi frame Indicator• H4 byte provides the multiframe information

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K3 – Automatic protection switching(APS) channel

• (b1-b4) are assigned for APS signaling for protection at the VC-4/3 path labels

N1 – Network operator Byte

• The tandem connection monitoring function is currently not used

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SDH Network SDH Network ElementsElements

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SDH Network Elements

• Terminal multiplexer

• Regenerator

• Add / Drop Multiplexer

• Cross – connect

Wide-band Digital cross connect

Broad band Digital cross connect

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Clock typeRelated CCITT

recommendation

Primary Reference Clock (PRC)

Slave clock (transit node)

Slave clock (local node)

SDH network-element clock

G.811

G.812

G.812

Under definition (G.81s)

Synchronization

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SDH Network SDH Network ManagementManagement

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SDH ManagementSDH management includes :

•ECC management

•Fault (maintenance) management :

Alarm surveillance

Testing

•Performance monitoring

•Configuration management

•Security management

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Error Performance :- G.82XParameters

• Errored second

• Errored second ratio

• Severely errored second

• Severely errored second ratio

• Background Block error

• Background block error ratio

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• Errored Second(ES) -A one-second period with one or more Errored Blocks (EB) for transmission speeds below 200 Mbits/s. Above this speed, the lowest number of errored blocks is to be defined.

Errored Second Ratio (ESR) - The ratio of ES to the total

seconds in available time during a measurement interval.

Severely Errored Second (SES) - A one-second period with one Errored Block Overstep (EBO) and/or one Severely Errored Block Overstep (SEBO).

Error Performance

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• Severely Errored Second Ratio (SESR) - The ratio of SES to the total seconds in available time during a measurement interval.

• Background Block Error (BBE) - An errored block, excluding blocks during SES and unavailable time.

• Background Block Error Ratio (BBER) - The ratio of errored blocks to the total blocks, excluding blocks during SES and unavailable time.

Error Performance

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Anomalies and Defects in Anomalies and Defects in SDHSDH

Alarms Anomalies / Defects Detection Criteria

LOS Loss of SignalDrop in incoming optical power level causes high causes high bit error rate

OOF Out of Frame A1, A2 errored for > 625 υs

LOF Loss of FrameIf OOF persists for > 3ms (to be defined)

RS BIP ErrorRegenerator Section BIP Error (B1)

Mismatch of the recovered and computed BIP-8 Covers the whole STM-N frame

RS-TIMRegenerator Section Trace Identifier Mismatch

Mismatch of the accepted and expected Trace Identifier in byte J0

MS BIP Error Mulitplex Section BIP Error (B2)Mismatch of thr recovered and computed N x BIP-24 Covers the whole frame except RSOH

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Anomalies and Defects in Anomalies and Defects in SDHSDH

Alarms Anomalies / Defects Detection Criteria

HP-UNEQ HO Path Unequipped C2 = 0 for > 5 frames

HP-TIMHO Path Trace Identifier Mismatch

Mismatch of the accepted and expected Trace identifier in byte J1

HP-REI HO Path Remote Error IndicationNumber of detected B3 errors in the sink side enc0ded in byte G1 (bits 1, 2, 3, 4) of the source side

HP-RDIHO Path Remote Defect Indication

G1 (bit 5) = 1 for > Z frames (Z = 3, 5 or 10)

HP-PLM HO Path Payload Label Mismatch Mismatch of the accepted and expected Payload Label in byte C2

TU-LOM Loss of MultiframeH4 (bits 7, 8) multiframe not recovered for X ms where X = 1 to 5

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Anomalies and Defects in Anomalies and Defects in SDHSDH

Alarms Anomalies / Defects Detection Criteria

TU-AISTributary Unit Alarm Indication Signal

All ones in the TU pointer bytes V1 and V2

TU-LOP Tributary Unit Loss of Pointer8 to 10 NDF enable 8 to 10 invalid pointers

LP BIP Error LO Path BIP Error

Mismatch of the recovered and computed BIP-8 (B3) or BIP-2 (V5 bit 1,2) Covers entire VC-n

LP-UNEQ LO Path UnequippedVC-3: C2 = 0 for > 5 frames VC-m (m=2, 11, 12) : V5 (bits 5, 6, 7) = 000 for > 5 multiframes

LP-TIMLO Path Tracr Indentifier Mismatch

Mismatch of the accepted and expected Trace identifier in byte J1(VC-3) or J2

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Anomalies and Defects in Anomalies and Defects in SDHSDH

Alarms Anomalies / Defects Detection Criteria

LP-RDILO Path Remote Defect Indication

VC-3: G1 (bit 5) = 1 for > Z frames VC-m (m=2, 11, 12): V5 (bit 8) = 1 for > Z multiframes (Z = 3, 5, 10)

LP-PLM LO Payload Label MismatchMismatch of the accepted and expected Payload Label in byte C2 or V5 (bits 5, 6, 7)