Basics on SDH and PDH

*The World of Synchronous Networks*Copyright by Stephan Schultz, Wandel & Goltermann Germany Box 1262, D-72795 Eningen u.A.e-mail: [email protected]://www.wg.com

All rights reserved.No parts of this book may be reproduced by any means, or transmitted, or translated without the written permission of the publisher.Basics on SDH from STM-1 up to STM-16

The World of Synchronous Networks

*The World of Synchronous Networks*Current Transmission Technologies


*The World of Synchronous Networks*The Telephone SystemLELE


*The World of Synchronous Networks*Audio SignalSampler OutputPulse Amplitude Modulated (PAM) signalSampling


*The World of Synchronous Networks*+Vdigital codes-VIn accordance with CCITTs A-law1/2V1/4V1/8V1/16V1/32V1/64VNon-Linear Quantization and Encoding


*The World of Synchronous Networks*8 bits per samplex=64kbit/s8000 samples per secPCM Signal Data Rate


*The World of Synchronous Networks*Time Division Multiplexing (TDM)


*The World of Synchronous Networks*PDH Systems Worldwide


*The World of Synchronous Networks*64 kbit/s Data Signals15 kHzSound ProgramSignals139264 kbit/s (+/-15ppm)2048 kbit/s (+/-50ppm)8448 kbit/s (+/-30ppm)34 368 kbit/s (+/-20ppm)64Channel Capacity:64 x 30 = 19200.3 to 3.1 kHzAF signalsDSMX34/140DSMX8/34DSMX2/8130DSMX64k/2130PCMX 301PCMX 305130PDH Multiplex / Demultiplex


*The World of Synchronous Networks*2.448 kbit/s frame: 32x8 bit=256 bit in 125sencoded voice / data signalsencoded voice / data signalssignallinginformationtimeslots0 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 31 2 Mbit/s Frame Structures


*The World of Synchronous Networks*Si: Reserved for international useSa4: Non urgent Alarm (0=Alarm)A: Remote alarm (1=urgent Alarm)

Sa4 to Sa8: Spare bits or used for message based data links (point-to-point applications)FAS: Frame alignment signal (0011011)NFAS: Non frame alignment signal2.448 kbit/s frame: 32x8 bit=256 bit in 125sencoded voice / data signalsencoded voice / data signalssignallinginformationtimeslots Si 1 A Sa Sa Sa Sa Sa 4 5 6 7 8FAS(frames 0,2,4...)NFAS(frames 1,3,5...) (M)0 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 31 2 Mbit/s Frame Structures


*The World of Synchronous Networks*Si: Reserved for international useSa4: Non urgent Alarm (0=Alarm)A: Remote alarm (1=urgent Alarm)Y: Remote MF alarm (1=Alarm)E: CRC error indication (0=Error)

Sa4 to Sa8: Spare bits or used for message based data links (point-to-point applications)FAS: Frame alignment signal (0011011)NFAS: Not frame alignment signalsignallingsubscr. nsignallingsubscr. n+152.448 kbit/s frame: 32x8 bit=256 bit in 125sencoded voice / data signalsencoded voice / data signalssignallinginformationtimeslots Si 1 A Sa Sa Sa Sa Sa 4 5 6 7 8FAS(frames 0,2,4...)NFAS(frames 1,3,5...) (M) 0 0 0 0 x Y x x a b c d a b c dMFASNMFASframe 0frames 1... 15 & 17...310 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 31 2 Mbit/s Frame Structures


*The World of Synchronous Networks*2.448 kbit/s Multiframe, ITU-T G.704fr 15fr 8fr 9fr 10fr 11fr 12fr 13fr 14fr 15multiframesub multiframe 1sub multiframe 2Si: Reserved for international useSa4: Non urgent Alarm (0=Alarm)A: Remote alarm (1=urgent Alarm)Y: Remote MF alarm (1=Alarm)

Sa4 to Sa8: Spare bits or used for message based data links (point-to-point applications)FAS: Frame alignment signal (0011011)NFAS: Not frame alignment signalsignallingsubscr. nsignallingsubscr. n+152.448 kbit/s frame: 32x8 bit=256 bit in 125sencoded voice / data signalsencoded voice / data signalssignallinginformationtimeslots Si 1 A Sa Sa Sa Sa Sa 4 5 6 7 8FAS(frames 0,2,4...)NFAS(frames 1,3,5...) (M) 0 0 0 0 x Y x x a b c d a b c dMFASNMFASframe 0frames 1... 15 & 17...310 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 31 2 Mbit/s Frame Structures


*The World of Synchronous Networks*2.448 kbit/s Multiframe, ITU-T G.704fr 15fr 8fr 9fr 10fr 11fr 12fr 13fr 14fr 15multiframesub multiframe 1sub multiframe 2Si: Reserved for international useSa4: Non urgent Alarm (0=Alarm)A: Remote alarm (1=urgent Alarm)Y: Remote MF alarm (1=Alarm)E: CRC error indication (0=Error)M: Transmitting CRC multiframe alignment signal ( CRC MFAS: 001011 )Sa4 to Sa8: Spare bits or used for message based data links (point-to-point applications)FAS: Frame alignment signal (0011011)NFAS: Not frame alignment signalsignallingsubscr. nsignallingsubscr. n+15 Si 0 0 1 1 0 1 1 Si 1 A Sa Sa Sa Sa Sa 4 5 6 7 8FAS(frames 0,2,4...)NFAS(frames 1,3,5...) (M) 0 0 0 0 x Y x x a b c d a b c dMFASNMFASframe 0frames 1... 15 & 17...31Time slot 0 of CRC multiframe:sub multiframe 1sub multiframe 20 FAS1 NFAS6 FAS7 NFAS8 FAS9 NFAS14 FAS15 NFAS256 X 8 bit = 2048 bit256 X 8 bit = 2048 bit2 Mbit/s Frame Structures2 Mbit/s Frame Structures


*The World of Synchronous Networks*8.448 kbit/s; frame length 848 bit; 100.4 us; ITU-T G.742 A: Alarm BitN: National Spare Bit1a: Stuffing Control BitS: Stuffing BitPlesiochronous Hierarchies - Frame Structures


*The World of Synchronous Networks*8.448 kbit/s; frame length 848 bit; 100.4 us; ITU-T G.742 34.368 kbit/s; frame length 1536 bit; 44.7 us; ITU-T G.751 A: Alarm BitN: National Spare Bit1a: Stuffing Control BitS: Stuffing BitPlesiochronous Hierarchies - Frame Structures


*The World of Synchronous Networks*139.264 kbit/s; frame length 2928 bit; 21 us; ITU-T G.751A: Alarm BitN: National Spare Bit1a,b,c,d: Stuffing Control BitS: Stuffing BitPlesiochronous Hierarchies - Frame Structures


*The World of Synchronous Networks*AISPDHEquipmentAISPDHEquipmentLOSLOFAISD-BitBER 10-3D-BitBER 10-6N-BitPDH Maintenance Signals


*The World of Synchronous Networks*OLTU34 - 1408 - 342 - 8OLTU34 - 1408 - 342 - 8OLTU34 - 1408 - 342 - 8OLTU34 - 1408 - 342 - 8mainstand-by140 Mbit/s140 Mbit/sLine Terminating UnitLine Terminating UnitDrop & Insert Station1,2 ................. 641,2 ................. 64Plesiochronous Drop & Insert


*The World of Synchronous Networks*The Synchronous Digital Hierarchy (SDH)


*The World of Synchronous Networks*Simpler multiplexing (low SDH level can be directly identified from higher SDH level)Simple D&I of traffic channels (direct access to lower level systems without synchronization)Allows mixing of ANSI and ETSI PDH systemsSDH is open for new applications (It can carry PDH, ATM, HDTV, MAN,...) SDH provides TMN (ECCs) (for centralized network control) Why SDH


*The World of Synchronous Networks*2Mbit/s 34Mbit/s 140Mbit/s STM-1 STM-4STM-1 / STS-3c Gateway to SONETTMDXCADMADM ATM SwitchSTM-4/-162Mbit/s34Mbit/s140Mbit/sSTM-1LAN2Mbit/sADMSTM-1STM-1, STM-42Mbit/s8Mbit/s34Mbit/s140Mbit/sADM : Add Drop Multiplexer DXC : Digital Cross Connect TM : Terminal MultiplexerDSC: Digital Switching CenterLAN: Local Area NetworkDSCSynchronous Network Structure


*The World of Synchronous Networks*Packet NetworkTelephone NetworkVC-3VC-4VC-11VC-12VC-2VC-3Multiplex section layerRegenerator section layerPhysical media layer. . . . . . Lower Order Path LayerHigher Order Path LayerSection LayerCicuit LayerSDH Transport LayerTransmission Media LayerLayered Model of the SDH Network


*The World of Synchronous Networks*VC-2VC-1VC-2VC-1VC-4VC-3VC-12VC-4VC-3VC-2VC-1VC-4VC-3VC-12VC-4VC-3RegS M XS M XMultiplexSectionRegenerator SectionsHigher Order PathLower Order PathSTM-nRSOHSTM-nRSOHSTM-n MSOHVC-4/3 POHVC-1/2/3 POHPath Denominations


*The World of Synchronous Networks*MUX /DEMUXMUX /DEMUXPDHPDHSDHSDHSDHReg.CCNNINNINNIITU-T Rec.:G.707BitratesG.708Signal Structure (NNI)G.709Synchronous Multiplex StructureG.703Electrical characteristicG.957Optical interface characteristic

The Network Node Interface (NNI) specifications are necessary to enable interconnection of synchronous digital network elements for transport of payloadsNetwork Node Interface (NNI)


*The World of Synchronous Networks*Bit Rates, Frame Structure and Interfaces in SDH


*The World of Synchronous Networks*ATM: 149.760 kbit/sE4: 139.264 kbit/sDS3: 44.736 kbit/sE3 : 34.368 kbit/s AUG C-4 TUG-3TU-3VC-3 C-3AU-3x1x3x7x7x3x1 STM-NSTS-3N AU-4STS-3C VC-4STS-3C SPESTS-1VC-3STS-1SPE TUG-2 VTgroupx3xNx1 x4DS1: 1.544 kbit/sTU-11VC-11 C-11VT-1.5VT-SPEE1: 2.048 kbit/sTU-12VC-12 C-12 VT-2VT-SPEITU-T G.707BELLCORE GR.253 ANSI T1.105ATM: 48,384 kbit/sDS2: 6.312 kbit/sTU-2VC-2 C-2 VT-6VT-SPEx1 STM-0 STS-1ETSISDH and SONET are International Standards


*The World of Synchronous Networks*RSOH: Regenerator section overheadMSOH: Multiplex section overheadPayload: Area for information transport

Transport capacity of one Byte: 64 kbit/sFrame capacity: 270 x 9 x 8 x 8000 = 155.520 Mbit/sFrame repetition time: 125 s13594270270 Columns (Bytes)19transmitrow by rowRSOHMSOHAU PointerPayload(transport capacity)STM-1 Frame Structure


*The World of Synchronous Networks*C-4STM-1 Frame Structure


*The World of Synchronous Networks*VC-4C-4VC-4 POHSTM-1 Frame Structure


*The World of Synchronous Networks*AU PointerAU-4VC-4C-4VC-4 POHSTM-1 Frame Structure


*The World of Synchronous Networks*13594270270 Columns (Bytes)19RSOHMSOHAU PointerSTM-1 Frame Structure


*The World of Synchronous Networks*12341234123412 . . . .11111222223333344444STM-1 #1STM-1 #2STM-1 #3STM-1 #4STM-4The STM-4/16 bit rate is obtained by byte-interleaved multiplexing of the STM-1 tributary signals.

Clock offset at the tributary side is taken into consideration by pointer adaptation on the STM-n output signal.

B1B2terminationnewHigher SDH Bitrates


*The World of Synchronous Networks*STM-4 SOHB1 and B2 bytes are being recalculatedBytes E1, F1, K1, K2, D1 to D3 and D4 to D12 are taken from tributary #1A U PointersPayloadSTM-4 Frame Structure


*The World of Synchronous Networks*Basic Elements of STM-1


*The World of Synchronous Networks*MUX /DEMUXMUX /DEMUXback-up linePDHPDHSDHSDHSDHMultiplex SectionReg.CCclockclockclockB1B1B3B2Parity BytesF2E1, F1, D1 ... D3E2, D4 ... D12Comm.ChannelsSynchronous Network


*The World of Synchronous Networks*AU - PTRVC-3/4 POHVC-11/12/ 2 POHSTM-1 SOHMedia dependent bytes

X Reserved for national use

SOH: Section overheadPOH: Path overheadThe overheads (SOH, POH) are used for maintenance and supervision of the SDH transmission network.Embedded Overhead Bytes


*The World of Synchronous Networks*Parity check (B1 calculated by regenerator and multiplexers) Data communication channels (D1...D3, F1 between regenerators) Voice communication channels (E1 between regenerators)Frame Alignment (A1, A2) Section Trace (J0 Identfication of regenerator source)Functions of Regenerator Section Overhead


*The World of Synchronous Networks*Parity check (B2)Alarm information (K2)Remote error indication (M1,K2)Automatic protection switching (K1, K2 Bytes)Data communication channels (D4 to D12 between multiplexers)Clock source information (S1)Voice communications channels (E2 between multiplexers)Functions of Multiplexer Section Overhead


*The World of Synchronous Networks*Parity check B3, V5/ BIP-2 calculated by path terminating pointAlarm and performance information (V5, G1)Structure of the VC Signal label C2Multiframe indication for TUs (H4)User communications channel between path elements (F2, F3)Identification of the Path Source (Path Trace J1, J2)J1B3C2G1F2H4F3K4N1V5J2N2K4VC-3/4 POHVC-11/12/2 POHFunctions of Path Overhead


*The World of Synchronous Networks*The Container (C)Basic packaging unit for tributary signals (PDH)Synchronous to the STM-1Bitrate adaptation is done via a positive stuffing procedureAdaptation of synchronous tributaries by fixed stuffing bitsBit by bit stuffingThe Virtual Container (VC)Formation of the Container by adding of a POH (Path Overhead)Transport as a unit through the network (SDH)A VC containing several VCs has also a pointer areaFunctions and Characteristics of the Individual Elements of the NNI


*The World of Synchronous Networks*The Tributary Unit (TU)Is formed via adding a pointer to the VCThe Tributary Unit Group (TUG)Combines several TUs for a new VCThe Administrative Unit (AU)Is shaped if a pointer is allocated to the VC formed at lastThe Syncronous Transport Module Level 1 (STM-1)Formed by adding a Section Overhead (SOH) to AUsClock justification through positive-zero-negative stuffing in the AU pointer areabyte by byte stuffingFunctions and Characteristics of the Individual Elements of the NNI


*The World of Synchronous Networks*Overhead Byte Functionality


*The World of Synchronous Networks*ContainerVirtual ContainerAdministrative UnitSynchronous Transport ModulePath OverheadPointerSection OverheadPlesiochronous signal140Mbit/sC4VC-4AU-4STM-1The way of integrating PDH signals into STM-1


*The World of Synchronous Networks*The pointer technology provides a means to accommodate timing differences at SDH networks.The pointer indicates the start of the payload within a STM-1frame.VC-4 POHVC-12 POHVC-12VC-4STM-1Pointers


*The World of Synchronous Networks*Opportunity fornegative stuffing(more capacity)Pointerinc/decIDIDIDIDNDF,mapping struc,pointer inc/decJ1C4 payload 0 1 1 0 1 0 0 1 1 0 0 1 X X X X X X X X X X X X X X X X X X X X 1 0 0 1 S S 1 1 1 1 1 0 0 0 0 0 Opportunity forpositive stuffing(less capacity)Pointer interpretation :New data flag (NDF) disabled : New data flag enabled : AU/TU type AU-4/TU-3 : AU/TU type AU-3/TU-3 : AU-4 pointer 0...782 : TU-3 pointer 0...764 : Null pointer indication (NPI) : Use of the AU-4 Pointer Area, Coding


*The World of Synchronous Networks*Frequency justification of several STM-1 signals running into a network node (Pointer Stuffing)RSOHMSOH H1 H2 H3RSOHMSOH H1 H2 H3 19270RSOHMSOH H1 H2 RSOHMSOH H1 H2 H3125s250s375s500sStart of VC-4negative justification byte (data)Pointer with inverted D bitsNew pointerActual pointerNot Synchronous SDH Networks


*The World of Synchronous Networks*AU PointerRSOHMSOHJ1B3C2G1F2H4Z3K3Z520 x 13 bytes per row

C-4140 Mbit/sC-4 transport capacity: 260 x 9 x 64 kbit/s = 149.760 kbit/sContainer C-4 contains a 140 Mbit/s PDH TributaryMapping 140 Mbit/s


*The World of Synchronous Networks*W = I I I I I I I IY = RRRRRRRR X = CRRRROOOZ = I I I I I I SRI = Information bitS = Justification opportunity bitR = Fixed stuffing bitC = Justification control bitO = Overhead bitThe figure shows one row of the VC-496 IW96 IY96 IY96 IY96 IX96 IX96 IX96 IY96 IY96 IY96 IY96 IY96 IX96 IY96 IY96 IY96 IZ96 IY96 IX96 IYJ1Mapping of a 140 Mbit/s Tributary into VC-4


*The World of Synchronous Networks*AU PointerRSOHMSOHJ1B3C2G1F2H4Z3K3Z5 H1 H1 H1 H2 H2 H2 H3 H3 H3fixed stuffingContainer C-4 contains 3 times a 34 Mbit/s PDH Tributary (ETSI structure)C-3 transport capacity: 84 X 9 x 64 kbit/s = 48.384 kBit/sVC-3 #1VC-3 #2VC-3 #3VC-4 POHVC-3 POHMapping 34 Mbit/s


*The World of Synchronous Networks*RSOHMSOHAU pointerVC-4TUG-3TUG-2TU-12VC-12Tu pointerMapping 2 Mbit/s


*The World of Synchronous Networks*AU-4 PointerRSOHMSOHJ1

B3

C2

G1

F2

H4

Z3

K3

Z51 2 3 4 5 6 7 8 9 10...........................................261 A B C A B C AA B CS T U F F I N GS T U F F I N G186TUG-3(A)186TUG-3(C)186TUG-3(B)Mapping and Multiplexing (1)


*The World of Synchronous Networks*1 2 3 4 5 6 7 8 9 10...........................................86 NPI

E3 F3 G3S T U F F I N GS T U F F I N GA1 B1 C1 D1 E1 F1 G1 A2 1 2 3 1 2 3 1 2 3 1 2 3 TU-12#1TUG-2(A)TU-12#3.....1 2 3 1 2 3 1 2 3 1 2 3TU-12#1TUG-2(B)TU-12#3.....TU-12#1TUG-2(G)TU-12#3.....TUG-3NPI: Null Pointer Indication1001 XX11 1110 0000 XXXX XXXXTU-12s occupy 36 bytes per frameMapping and Multiplexing (2)


*The World of Synchronous Networks*V5: VC-12 Path OverheadR: fixed stuffing bitsJ2: Path TraceC1/2: Justification control bitO: Overhead bitN2: Network Operator byteK4: APSS2: Justification opportunity bitI: Info-bitPayloadVC-4 PayloadV4XXX XX00PayloadVC-4 PayloadV1XXX XX01PayloadVC-4 PayloadV2XXX XX10PayloadVC-4 PayloadV3XXX XX11PayloadVC-4 PayloadV4XXX XX00VC-12 Structure:H4: Indicates the number of VxV1,V2,V3: TU-12 PointerH4H4H4H4H4VC-4 POHMapping 2 Mbit/s (asynchronous)


*The World of Synchronous Networks*AU-4 PointersMSOHRSOHSTM-4VC-4-4cJ1C2G1F2H4F3K3N1C-4-4cFixed StuffFixed StuffFixed Stuff4 x 9 bytes4 x 261 bytes4 x 261 bytesATM CellThe first Pointer indicates J1All other Pointers are set to "Concatenation Indication"B3VC-4 Contiguous Concatenation


*The World of Synchronous Networks*ATM switchSDH cross-connect for VC-4ATM switch

150 Mbit/s

600 Mbit/sVC-4-4cSTM-4c portSTM-4c portSTM-4 portSTM-4 port

150 Mbit/s

150 Mbit/s

150 Mbit/s ?VC4VC4VC4VC44 xDifferentdelays for VC-4's?How to transport 600 Mbit/s ATM via 150 Mbit/s SDH?


*The World of Synchronous Networks*Generation:All Pointers are set to the same valueAll VC-4 should be kept in the same STM-4All VC-4 are transported as individual VC-4'sVC-4 Virtual Concatenation (Generation)


*The World of Synchronous Networks*Termination:VC-4-4vc is reconstructed using the (different) pointer values for alignment

VC-4 Virtual Concatenation (Termination)


*The World of Synchronous Networks*E4: 139.264 kbit/sDS3: 44.736 kbit/sE3 : 34.368 kbit/s AUG C-4 TUG-3TU-3VC-3 C-3AU-3x1x3x7x7x3x1 STM-NSTS-3N AU-4STS-3C VC-4STS-3C SPESTS-1VC-3STS-1SPE TUG-2 VTgroupx3xNx1 x4DS1: 1.544 kbit/sTU-11VC-11 C-11VT-1.5VT-SPEE1: 2.048 kbit/sTU-12VC-12 C-12 VT-2VT-SPESDHSONETITU-T G.707BELLCORE GR.253 ANSI T1.105ATM: 149.760 kbit/sATM: 48,384 kbit/sDS2: 6.312 kbit/sTU-2VC-2 C-2 VT-6VT-SPEx1 STM-0 STS-1SDH and SONET are International Standards


*The World of Synchronous Networks*STS-1 frame structure for SONET systemsTOHSPE9 Rows38790 Bytes125 sThe STS-1 bit rate = 810 bytes/frame x 8 bits/byte x 1 frame/125 s or STS-1 = 51.840 Mb/s TOH = Transport Overhead SPE = Synchronous Payload Envelope


*The World of Synchronous Networks*Asynchronous DS-3 mapping (SONET)The first column of the SPE (9 bytes) is taken up by STS-1 path overhead (POH) Remaining 86 columns are treated as a single bundle. The complete STS-1 payload envelope is about 51Mb/s : DS-3 is 44736 Mb/s - approximately 5 Mb/s of insert stuffing must be added.

SPEAsync DS-3Signal LabelC2User ChannelF2TraceJ1BIP-8B3Path StatusG15

IndicatorH4GrowthZ3GrowthZ4TandemZ5FramingA1BIP-8B1Data ComD1FramingA2OrderwireE1Data ComD2STS-IDC1UserF1Data ComD3PointerH1Bip-8B2Data ComD4Data Com D7Data ComD10Sync StatusZ1PointerM2APSK1Data ComD5Data ComD8Data ComD11FEBEZ2APSK2Data Con D6Data ComD9Data ComD12OrderwireE2Line OHSection OHPointer ActionH387 columns3 columns


*The World of Synchronous Networks*SDH Network Elements


*The World of Synchronous Networks*SDH Network ElementsSDH RepeaterSTM-nSTM-nApplications:Line Signal Regenerationin Point-to-Point and Ring NetworksTerminal MultiplexerSTM-nPDH & STM-mTributariesm

*The World of Synchronous Networks*Add Drop Multiplexer


*The World of Synchronous Networks*Synchronous Cross Connect


*The World of Synchronous Networks* Optical Receive UnitSync DEMUX Optical Transmit UnitSync MUX4444Management Communication UnitService Channel UnitOverhead Processing UnitData ChannelsService ChannelsPC / TMN (Q)16 x 140 Mbit/s or 16 x STM-116 x 140 Mbit/s or 16 x STM-1STM-16STM-16SLX 1/16Synchronous Line Equipment


*The World of Synchronous Networks*2Mbit/s 34Mbit/s 140Mbit/s STM-1 STM-4SDHADM : Add Drop Multiplexer DXC : Digital Cross Connect TM : Terminal MultiplexerHybrid Networks Connect Old and New Technologies


*The World of Synchronous Networks*Local NetworkSTM-4STM-16STM-1STM-1ExchangeFlexMuxSubscriberAccessMux64/2MLocalExchangeTrunk NetworkL 1Trunk NetworkL 2SDH Network TopologyTrunk Network L 2


*The World of Synchronous Networks*Synchronization Architecture in SDH


*The World of Synchronous Networks*Synchronization NetworkPrimary Reference ClockSynchronization Supply UnitSDH Equipment ClockCaesium (Stratum 1) requ : 1 x 10-11 typ : 5 x 10-12 long term: holdover 24h:Rubidium (Stratum 2) requ : 1.6 x 10-8 , 1 x 10-10 typ : 4 x 10-11 , 2 x 10-11


*The World of Synchronous Networks*Limits:

Max. 10 x G.812 TNCMax. 60 x G.813 SEC, though no more than 20 between 2 TNCsG.811 PRCG.812 TNCG.812 TNCG.813 SECG.813 SECG.813 SECSSUSSUSynchronization reference model


*The World of Synchronous Networks*Synchronization of SDH Network ElementsSynchronousSDH SignalSDH Network Element


*The World of Synchronous Networks*Phase error [ ns]Observation interval [s]0.0111001000010100100010000100000Hold-over mode


*The World of Synchronous Networks*Hold-over measured values (TIE)


*The World of Synchronous Networks* ITU-TANSI / BellcoreETSI Definitions G.810T1.101 / GR-253ETS 300 462-1Network G.825T1.105 / GR-253ETS 300 462-3Primary Reference Clocks G.811T1.101ETS 300 462-6Synchron. Supply Clocks (ST2) G.812T1.101ETS 300 462-4Equipment Clocks (ST3) G.813 (G.81s)GR-253ETS 300 462-5Which Recommendations define Synchronization Networks


*The World of Synchronous Networks*Monitoring, Maintenance and Control Functions in SDH


*The World of Synchronous Networks*LOSLoss Of SignalLOS Loss Of Signal TSETest Sequence Error (Bit Err.)TSE Test Sequence Error LSSLoss of Sequence Synchron.LSS Loss of Sequence Synchr. LTILoss of incoming TimingRef.LTI Loss of inc. TimingRef OOFOut Of FrameOOFOut Of Frame LOFLoss Of FrameLOFLoss Of Frame B1Regenerator Section BIP Err.B1Section BIP Errors B2Multiplex Section BIP Err.B2Line BIP Errors MS-AISMultiplex Section AISAIS-LLine AIS MS-RDIMux Sect. Remote Defect Ind.RDI-LLine remote Defect Ind. MS-REIMux Sect. Remote Errro Ind.REI-LLine Remote Error Ind. AU-LOPLoss Of AU PointerLOP-PSP Loss Of Pointer AU-NDFNew Data Flag AU PointerNDF-PSP New Data Flag AU-AISAU Alarm Ind. SignalAIS-PSP AIS AU-PJEAU Pointer Just. Event B3HO Path BIP ErrorsB3SP BIP Errors HP-UNEQHO Path UnequippedUNEQ-PSP Unequipped HP-RDIHO Path Remote Defect Ind.RDI-PSP Remote Deect. Ind. HP-REIHO Path Remote Error Ind.REI-PSP Remote ERrro Ind. PDI-PSP Payload Defect Ind. HP-TIMHO Path Trace Ident. MismatchTIM-PSP Trace Ident. Mismatch HP-PLMHO Path Payload Label Mism.PLM-PSP Payload Label Mismatch TU-LOPLoss Of TU PointerLOP-VVP Loss Of Pointer TU-NDFNew Data Flag TU PointerNDF-VVP New Data Flag TU-AISTU AISAIS-VVP AIS TU-LOMLoss Of MultiframeLOMLoss Of Multiframe BIP-2/B3LO Path BIP ErrorsBIP-2VP BIP Errors LP-UNEQLO Path UnequippedUNEQ-VVP Unequipped LP-RDILO Path Remote Defect Ind.RDI-VVP Remote Defect Ind. LP-REILO Path Remote Error Ind.REI-VVP Remote Error Ind. LP-RFILO Path Remote Failure Ind.RFI-VVP Remote Failure Ind. PDI-VVP Payload Defect Ind. LP-TIMLO Path Trace Ident. MismatchTIM-VVP Trace Ident. Mismatch LP-PLMLO Path Payload Label Mism.PLM-VVP Payload Label Mism.Mux Sect.Phys./Reg.Sect.Higher Order PathLower Order PathPhys./SectionLCDLoss of Cell DelineationI.610HCORCorrectable Header ErrorsHUNCUncorrectable Header ErrorsVP-AISVirtual Path AISI.610VP-RDIVirtual Path Remote Defect IndicationI.610VC-AISVirtual Channel AISI.610VC-RDIVirtual Channel Remot Defect IndicationI.610Vx-AISVirtual Channel AIS & Virtual, Path AIS simultan.(O.191)Vx-RDIVirtual Channel RDI & Virtual, Path RDI simultan.(O.191)LOCLoss Of ContinuityI.610ATM PathEVENTS SDHEVENTS SONET


*The World of Synchronous Networks*Frame Areas Covered by Parity BytesRSOHMSOHPayloadB1:- Supervision of the whole STM-1 frame- Covers the regenerator sections of a transmission systemB2:- Covers the multiplex sections (from network node to network node)B3:- Covers the transmission paths from beginning to the end (tributary to tributary)RSOHMSOHPayloadPayloadRSOHMSOHParity bytes providing a means to supervise the transmission quality of a life STM-N signal !PayloadAU-PTR


*The World of Synchronous Networks*Parity Supervison ProcedureTransmit Side


*The World of Synchronous Networks*Parity Supervison ProcedureTransmit SideB1Receive Sideframe n+1frame nrecalculation at Rx side


*The World of Synchronous Networks*How to Built a Parity Byte ?Bit interleaved data field structure of the area coveredField width: BIP-24: 24 bits(B2) BIP-8: 8 bits(B1, B3) BIP-2: 2 bits(V5)Column by column parity check for even numbers of "1"BIP-24

8011 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1 1 0 0 0 1 1 1 0 1 0 1 0 0 0 1 1 0 0 1 1 1 0 0 1 0 1 0 1 0 0 1 1 1 1 0 1 0 1 1 0 0 1 0 0 0 1 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 1 11 1 0 1 0 1 0 1 1 0 1 1 0 1 0 0 1 1 1 0 0 1 0 11 0 0 1 0 0 0 0 1 0 1 0 0 0 0 0 1 0 1 0 1 0 0 0123Byte 1Byte 2Byte 3even numbers of "1"Example: 24 bit interleaved parity check (BIP-24)


*The World of Synchronous Networks*SDH MAINTENANCE INTERACTIONS


*The World of Synchronous Networks*LOSDrop of incomming optical power level causes BER of 10-3 or worseOOFA1, A2 incorrect for more than 625 usLOFIf OOF persists of 3msB1 ErrorMismatch of the recovered and computed BIP-8MS-AISK2 (bits 6,7,8) =111 for 3 or more framesB2 ErrorMismatch of the recovered and computed BIP-24MS-RDIIf MS-AIS or excessive errors are detected, K2(bits 6,7,8)=110MS-REIM1: Binary coded count of incorrect interleavedbit blocksAU-AISAll "1" in the entire AU including AU pointerAU-LOP8 to 10 NDF enable or 8 to 10 invalid pointersHP-UNEQC2="0" for 5 or more framesHP-TIMJ1: Trace identifier mismatchHP-SLMC2: Signal label mismatchHP-LOMH4 values (2 to 10 times) unequal to multiframesequence

B3 ErrorMismatch of the recovered and computed BIP-8HP-RDIG1 (bit 5)=1, if an invalid signal is received in VC-4/VC-3HP-REIG1 (bits 1,2,3,4) = binary coded B3 errors

Maintenance Signal Defenitions (1)


*The World of Synchronous Networks*TU-AISAll "1" in the entire TU incl. TU pointerTU-LOP8 to 10 NDF enable or 8 to 10 invalid pointersLP-UNEQVC-3: C2 = all "0" for >=frames;VC-12: V5 (bits 5,6,7) = 000 for >=5 framesLP-TIMVC-3: J1 mismatch; VC-12: J2 mismatchLP-SLMVC-3: C2 mismatch; VC-12: V5 (bits 5,6,7) mismatchBIP-2 ErrMismatch of the recovered and computed BIP-2 (V5)LP-RDIV5 (bit 8) = 1, if TU-2 path AIS or signal failure receivedLP-REIV5 (bit 3) = 1, if >=1 errors were detected by BIP-2LP-RFIV5 (bit 4) = 1, if a failure is declared

Abbreviations:

AUAdministration unitHPHigh pathLOFLoss of frameLOMLoss of miltiframeLOPLoss of pointerLOSLoss of signalLPLow pathOOFOut of frameREIRemote error indication (FEBE)RDIRemote defect indication (FERF)RFIRemote failure indicationSLMSignal label mismatch

TIMTrace identifierTUTributary unitUNEQUnequippedVCVirtual CcontainerMaintenance Signal Definitions (2)


*The World of Synchronous Networks*ESErrored SecondSecond with> 1errored block

SESSeverely Errored SecondSecond with > 30% errored blocks or > 1 defect

BBEBackground Block ErrorErrored block, not occuring as part ofSESITU-T G.826ESErrored SecondSecond with > 1 bit error

SESSeverely Errored SecondSecond with BER > 1 x 10E-3ITU-T G.821UASUnavailable Seconds:Performance Parameter


*The World of Synchronous Networks*Jitter and Wander


*The World of Synchronous Networks*0123456789. . .Time Line101101001100Bit Sequence1 UIIdeal Signal (NRZ)Actual Signal(with Jitter and Wander)Phase Variations (Jitter or Wander) in a Digital Transmission SystemJitter and Wander Definitions


*The World of Synchronous Networks*Interference signalsPattern dependent jitterPhase noiseDelay variationStuffing and wait time jitterMapping jitterPointer jitterSources of Jitter and Wander


*The World of Synchronous Networks*PatternClockSignalInputExt. Reference Clock Input (Wander Measurement)ClockInputN1ffVVPattern-Clock ConverterFrequency DividerPhase DetectorPhase Detector~ 1 HzFiltersHP LPPeak-to-Peak DetectorLow Pass FilterVCOJitter and Wander

Reference Clock Generator (PLL)Result EvaluationJitter and Wander Measurement Method


*The World of Synchronous Networks*Max. Jitter Amplitude:1,5UI0,15UIJitter Measurement Filters


*The World of Synchronous Networks*Jitter Amplitude (PP)Measurement PeriodJitter / UIppTimeDefinition of Jitter Peak-to-Peak Amplitude


*The World of Synchronous Networks*Network output jitter (G.825) Network element output jitter (G.783, G.813) Jitter transfer function (G.958) Jitter and Wander tolerance (G.825, G.813)Jitter and Wander Measurements


*The World of Synchronous Networks*Wander Long-term timing variation (below 10 Hz)

TIE"Time Interval Error"MTIE"Max. Time Interval Error"TDEV"Time Deviation", timing variation as a function of integration time. Provides information about the spectral content. TVAR"Time Variation", square of TDEV ADEV"Allen Deviation" MADEV"Modified Allen Deviation" Definitions specified in ITU-T Rec. G.810WANDER Definitions


*The World of Synchronous Networks*MTIEObservation PeriodStartEndWander / UITimeSlope representing Frequency OffsetTIE at t EndTIE maxTIE minTime variation against referenceTIE and MTIE Definition


*The World of Synchronous Networks*Results (MTIE) compared to Standards


*The World of Synchronous Networks*Network resilience


*The World of Synchronous Networks*Linear Protection (G.783)WPWPWWP1 + 1 Protection scheme1 : 1 Protection scheme1 : N Protection scheme


*The World of Synchronous Networks*Unidirectional and Bidirectional RingsBidirectional Ring- use the shorter or longer path - increase number of paths - short path : traffic long path : protection


*The World of Synchronous Networks*Unidirectional Path-Switched RingTributaryTributaryACBFDEFiber 2 : unidirectionalFiber 1 : unidirectional


*The World of Synchronous Networks*Unidirectional Path-Switched Ring


*The World of Synchronous Networks*Unidirectional Path-Switched RingTributaryTributaryACBFDEFiber 2 : unidirectionalFiber 1 : unidirectional


*The World of Synchronous Networks*Unidirectional Line-Switched RingTributaryTributaryACBFDEProtectionWorkingWorking


*The World of Synchronous Networks*Two fiber Bidirectional Line-Switched Ring (BLSR)workingprotection


*The World of Synchronous Networks*Two fiber Bidirectional Line-Switched Ring (BLSR)TributaryABFCDE TributaryFiber 1Fiber 2workingprotection


*The World of Synchronous Networks*Four fiber Bidirectional Line-Switched Ring (BLSR)


*The World of Synchronous Networks*Four fiber Bidirectional Line-Switched Ring (BLSR)TributaryABFCDE TributaryProt.Fiber 3 + 4Working Fiber 1 + 2


*The World of Synchronous Networks*Four fiber Bidirectional Span-Switched RingTributaryABFCDE TributaryProt.Fiber 3 + 4Working Fiber 1 + 2


*The World of Synchronous Networks*TMN in SDH networks


*The World of Synchronous Networks*Network ManagementBasic tasks of network management:

Administrative functions:

Operation:Network supervising (anomalies, defects)Network linking(reserve links, additional links)

Maintenance:Identifing and elimination of impairmentsPlanning and commissioning:Network configuration

Operative functions:Supervision of network functionsRepairInstallationSelf test


*The World of Synchronous Networks*TMN Overlay


*The World of Synchronous Networks* Performance Faults Configuration Accounting SecurityManagement of :DXCDXCLocal OSXXQ3Q3Q3QECCADMADMADMADMQECCQ3Data Communication Network : X.25, ISDN, LANTelecommunication Management Network (TMN) OverlaySTM-NSTM-NSTM-N


*The World of Synchronous Networks*TMN Reference ConfigurationOperating System OSMediation Device MDNetwork Element NEData Communication NetworkDCNNetwork Element NEFFFQ3Q3Q2 or Q1QxQ3WorkstationWorkstationWorkstationMD: Conversion between different interfaces(Information Conversion Function ICF:manufacturer-specific information model ->operator specific information model)Local Communication NetworkLCN


*The World of Synchronous Networks*Interoperability in TMNQMonitor provideseasy adaptation to the interface (autoconfiguration)decoding of protocols and management informationautomatic detection of errors in management informationSDH/SONET Qecc access with transmission analyzers (e.g. ANT-20)QMonitor based on DominoWANDominoLAN DA-30Interoperability problems because ofmulti vendor networksheterogenous technologydifferent standards for protocols and management information


*The World of Synchronous Networks*SDH Benefits


*The World of Synchronous Networks*Pirelli : WaveMux 3200 32 x OC-48 channels 80Gbit/s over 1200km40 x OC-48 channels 100Gbit/s over 600kmCiena : There may not be a near term need, but this is the direction that networking will take next for 3 or 4 years.Ryan, Hunkin, Kent Consulting '96Future Trends - WDM SystemsCurrent Systems : 4, 8, 16 x OC-48 (MCI, Sprint)


*The World of Synchronous Networks*Future Trends - Optical ComponentsADMOptical D&I Local Traffic 2Mbit/s, DS-3, STM-1 l1, l2, l3, l4 l2 l1, l2, l3, l4 l2WDMWDMSTM-N, OC-NSTM-N, OC-N Extract selectively Minimize need for demultiplexing entire bandwidth


*The World of Synchronous Networks* STM-16c VC2-5c PoS STM-64 DWDM Larger CapacityOptical NetworksAdditional MappingsFutureTrends in Synchronous Technology TMN Q3 Worldwide


*The World of Synchronous Networks*Lets summarize !Please name the PDH bitrates !Please explain stuffing !When will stuffing be applied ?What is the reaction of a Network element after an LOS alarm ?What is the meaning of an LOF alarm ?Is it possible to drop an 2Mbit/s signal out of an 140Mbit/s line ?Why not ?Please name the SDH bitrates !Explain the way an PDH signal is integrated in an STM-1 !


*The World of Synchronous Networks*Lets summarize !Please name the different sections of an SDH connection !What is a parity byte ?Please explain the way to build a parity byte !Which parity bytes do you know ?Which overhead bytes are used for data communication ?What is a pointer ?What is a pointer used for ?


*The World of Synchronous Networks*Lets summarize !Please name the SDH network elements !What are they used for ?Please explain how a synchronization network looks like !What is a holdover mode ?Which byte is used to transport an HP-UNEQ ?Please explain Jitter and Wander !How can jitter be defined ?Please explain the terms TIE and MTIE ?Please explain the term TDEV ?Explain the possibilities to synchronize a NE !


*The World of Synchronous Networks*Lets summarize !Please name the main Jitter and Wander measurements !Explain these measurements !Please explain the methods of linear protection !What kind of ring structures do you know ?Please explain DWDM !What are the the advantages of a TMN controlled network ?How is the TMN interface called ?


*1 Current transmission technologies1.1 A brief history of transmission systems1.2 Principle of Plesiochronous Operation 1.3 Stuffing techniques1.4 Problems of PDH2 The Synchronous Digital Hierarchy (SDH)2.1 Synchronous Naetwork Structure2.2 Origins of SDH and SONET2.3 Principles of SDH2.4 Line and Network interfaces3 Bit rates, frame structure and interfaces3.1 ITU-T and SONET multiplex structure3.2 STM-1 frame structure3.3 STM-N frame structure3.4 Multiplex principles and specification4 Basic elements of STM-14.1 Digital signal sections4.2 The Section Overhead (SOH)4.3 The Path Overhead (POH)4.4 Pointer activities 4.5 Mapping procedures

5 SDH Network Elements5.1 Add & Drop Multiplexer5.2 Terminal Multiplexer5.3 Crossconnect6.3 SDH Topology6 Synchronization architecture in SDH6.1 Clock hierarchy6.2 Evaluation methods and standards7 Monitoring and maintenance functionality7.1 Bit error monitoring with BIP-N test7.2 SDH Maintenance Signal Interactions7.3 Jitter and Wander7.4 SDH measurement techniques7.5 TMN, Telecommunication Management Network8 International SDH Network Standards8.1 The evaluation of Synchronous Standards8.2 Relevant ITU-T Recommendations8.3 ETSI Standards9 Future Trends in SDH**When telephony began more than 100 years ago, only one speech connection at a time could be made, using a specific pair of copper wires. Speech was transmitted as analogue electrical signals, corresponding to its tonal variations. As technology progressed, digitalisation was introduced into telephony, improving transmission reliability and resulting in better use of cables. However signals from subscribers are transmitted in analogue form, making a digitalisation process necessary.

*Sampling is the periodical measurement of the value of the analogue signal. A sampled signal contains all the information if the sampling frequency is at least twice the highest frequency of the signal to be sampled.As the analogue signals in telephony are band-limited from 300 to 3400Hz, a sampling frequency of 8000Hz - every 125usec - is sufficient.

*The amplitude of a typical telephone speech signal can vary enormously, both from one speaker to another and over the normal speaking range of a single individual. In fact, the range of variation can be as great as 50 - 60dB.With a human voice the low level signals are more important than the high levels, so using quantization levels which are closer together at lower amplitudes and get wider as the amplitude increases is more efficient. This is known as non-linear encoding and has two CCITT recommendations A-law >> European >>E1 systemu-Law (mu-law) >> USA >> T1 system8-bit/s used in non linear coding would require an equivalent 12-bit/s in linear coding.*Each telephone channel has a PCM signal which is the analogue signal sampled at 8kHz and then is non-linearly encoded with 8 bits giving 64kbit/s data rate.

*As you saw earlier an encoded telephone speech signal is transmitted at rate of 64kbit/s (8 bits /sample; 8kHz sampling frequency).However, long distance telephone trunks are designed to handle data at a much greater rate then this.It therefore makes sense for a number of channels to share the same transmission link, using the technique of Time Division Multiplexing (TDM).In the diagram a separate encoder and decoder is shown for a 4-channel multiplexed system.The complete signal is divided into repeated sequences of four successive time slots.When transmission begins, time slot 1 is used to transmit the 8 bit code for the first sample of channel 1; time slot 2 is then used to send the first sample of channel 2...... ....after four slots have elapsed the process begins again, with time slot 1 containing the second sample of channel 1 and so on.*The first digital multiplex systems were introduced at the beginning of the 1970s. The introduction of digital exchanges for 64kbit/s channels increased the pressure to bunch together great numbers of channels for digital transmissions. Three international multiplex hierarchies arose. The bitrates for these hierarchies were standardized gradually. The primary level of the hierarchies is synchronous, but the synchronization technique varies depending on the network and 64kbit/s interfaces of the primary multiplexer.Central clock synchronisation is the predominant technique in the telephone network. this technique makes use of a central clock which is fed hierarchically to the switching devices*What are Plesiochronous Tributaries?ITU-T define plesiochronous digital hierarchy tributaries with a certain permitted deviation of bitrate. Each multiplexer has its own clock source (oscillator), making the accuracy of the output frequency vary from system to system. Tolerance ranges have been standardized for the bit rate accuricy. These systems are described as "free running" and networks based on such systems are "plesiochronous".("plesio-" comes from the Greek word for "near" since these systems are nearly synchronous.)*****In the 2048kbit/s primary frame, 30 message channels and a signalling channel follow the frame alignment signal (FAS, which alternates with the not frame alignment signal, NFAS). The frame is 125s long. Each channel can be identified by its byte position following the FAS or NFAS. However, this synchronous frame structure could not be maintained at the higher hierarchy levels.**Clock frequeny adaptation in multiplexers.Special measures are necessary to allow transmission of tributaries without slips. A clock is generated for each tributary while the actual signal is written into an elastic buffer. To generate the frame, the signal is read from the buffer at a slightly higher clock rate. Any variation in the signals are then compensated using stuffing (also known as justification). Stuffing bits are reserved in the generator frame for this purpose. Depending on how full the elastic buffer is, either data or stuffing bits are written to the frame. Stuffing information bits are also included in the frame to let the demultiplexer know which bits are date and which are stuffing. The demultiplexer generates the tributary bit rate once the stuffing bits have been eliminated.The effects of plesiochronouos operation become clearer when we examine how the bit rates are computed. TRj+1 = m x TRj + deltaThe tributary bit rate (TRj) is multiplied by the multiplex factor (m). Additional transmission capacity is required for activities such as frame marking, service signalling and stuffing. The additional capacity required varies at each hierarchy level and the multiplex factores vary outside Europe. This variable frame structure has caused a number of technical difficulties.*Stuffing techniques:We will look at stuffing procedures in more detail since it is also used in SDH.Fixed stuffing is the simplest form. The additional bits contain no information. They are used to achiev a specified bit rate.Positive stuffing is used in PDH. Tributary bits are written from the elastic buffer to the stuffing locations. If the data in the buffer drops below a specified level, stuffing begins and the tributary bits are left out.Negative stuffing is the inverse of this process. Tributary bits are written into the stuffing locations when the elastic buffer is filled past a given threshold.In positive negative stuffing, the additional bit rate is divided between both processes. There are two different stuffing positions - one for positive and one for negative stuffing*Although a number of problems arise in PDH systems. The frame generation procedure leaves almost no space to implement additional functions such as alarm generation. The plesiochronous systems are normally "dump" systems meaning that they cannot react to a conflict. Only demultiplexers have access to the message channels on the certain hierarchy levels.Only a few alarm indications are possible on PDH systems.*Another problem is that insertion of 2 Mbit/s channels into e.g. a 140Mbit/s local line requires a minimum investment of 4 systems (3 multiplex systems and 1 terminal equipment. Mechanical switching equipment is used for the most part. Although electronic routers have been developed for 64kbit/s and 2 Mbit/s channels. The development cost associated with plesiochronous technology are too high for the upper hierarchy levels.To access a single channel (e.g.64 or 2048 kbit/s) of a multiplex signal it is necessary to go twice through the whole multiplex chain (redundacy of hardware).**These are only some advantages where we will go into more detail later on.First let's have a look to the synchronous network structure.*Here we must consider the telecommunications network as a whole. In the area of the subscriber network nodes the users are connected to the exchanges (DSC) via the user network interface (UNI). Instead of this central switching points local cross connects (DXC) should be used. In a PDH network a fixed network is performed by point to point links. The channels are switched via these links. Signals from other networks use this transmission technology via flexible multiplexers up to 2 Mbit/s. The growth in data traffic is much higher than in voice communication. The greatest demand lies in the area of high bit rate access from the subscriber area. Such transmission capacity should be available at a reasonable cost and on short notice. The Terminal multiplexer (TM) with diverse interfaces feed this traffic into the SDH network directly or via Add and Drop Multiplexers (ADM) which are configured in a ring network (Back Bone). This ring is formed by two fibre optical cables with variouse back-up switching possibilities. The Network Management (TMN) sets up the necessary connections.*Here we see the layerd model of the SDH network. Various networks provide the basic services in the Circuit Layer:Line-switched services Packet-switched services Leased lines Broadband servicesIn the Path Layer two fully independent layers can be introduced due to the VC (Virtuel Container) concept.The Transmission Layer encompasses the digital signal sections and the physical medium.*Here we see it once again in a different view.*Recommandation G.708 indicates the range of validity of the NNI along with its functions. (rec. G.707 specifies the SDH bit rates).Tributary signals enter the SDH network via a synchronous multiplexer. Network elements are always connected via the NNI. This means that various transmission medias such as radio links and cables must include this interface. SDH systems always use framed signals since the basic element is the synchronous transport module (STM). Cross connect systems are the heart and as such they determine the structure of the trunk network. The physical specifications for the NNI are contained in Re. G.703 (electrical) and G.957 (optical).**The European Telecommunications Standard Institute (ETSI) did not accept the elements unneeded in Europe (AU-3, VC-3, C-2 and TU-11). 1.5 Mbit/s signals are transported in Europe within the VC-12.*A STM-1 signal has a byte-oriented structure with 9 rows and 270 columns. A distinction is made between three areas:the payload area, which uses 261 columnsthe pointer areathe section overhead, which is splittet up into two parts the Regenerator- and the Multiplex-Section Overhead.Each byte corresponds to a 64kbit/s channel. The overall bit rate of the STM-1 frame corresponds to 155.520 Mbit/s. The frame repetition time is 125s.

****A STM-1 frame is built-up in the following way. A basic unit known as a container (C) is formed from plesiochronous signals. Stuffing is used to give the plesiocronous signals a fixed bit rate. The clock frequency of the signal is adapted using positive or positive - zero - negative (bit) stuffing. The container bit rate itself is formed through an addidional fixed stuffing process. The container is nominally synchronized to the STM-N frame.Insertion of the path overhead (POH) produces a virtual container (VC). The transmission paths through the SDH network are formed by these VCs which are the smallest transport units in SDH. This means that a VC has to be terminated at the end of a path at the SDH/PDH transition point.The VCs are coupled to the STM-1 frame by pointers (PTR) These pointers are used along with stuffing techniques (byte-stuffing) to compensate for unavoidable phase fluctations and other interferences which occurs in synchronous operating. The pointer and the VC forms the Administrative Unit (AU). Finally the Administrative Unit Group (AUG) or STM-1 is formed by adding the SOH.*The higher hierarchies of a SDH signal are obtained by a byte-interleaved multiplex procedure of the STM-1 tributary signals. There is no additional overhead neccessary as we know from the PDH systems. The bitrate on the output of the multiplexer is exactly four times (STM-4) or sixteen times (STM-16) the bitrate of the STM-1 signal. STM-1: 155.520 Mbit/sSTM-4: 622.080 Mbit/sSTM-16:2.488.320 Mbit/s (STM-64:9.953.280 Mbit/s)

*STM-4 Overhead:The overhead capacity is four times the capacity of the STM-1 signal. But not all bytes are used because it makes no sence to transmit four times the same information.**The SDH transmission network is splitted up into different sections.The Regenerator Section between regenerators.The Multiplex Section between Multiplexers or Cross Connects.The Path between the termination points.*A number of functions are defined in the overhead channels to ensure proper transport of the payload.The Section Overhead (SOH)The overall capacity of the SOH is 4.608 Mbit/s (9x8x64kbit/s), of which 30 bytes (1.920 Mbit/s) have fixed definitions. The remaining 64kbit/s channels are not specified. Six are reserved for national use. Although six bytes are reserved for medium dependent functions (e.g. radio link systems). The columns 1,4 and 7 corresponds also to the STS-1 frame.Functions of the SOH:Contains maintenance, monitoring and operational functionsEach byte refers to a 64kbit/s channelSplitted into RSOH and MSOHProtect the connection from point of STM-1 assembly to point of disassembly.The Path Overhead (POH)The POH of VC-4/VC-3 consists of 9 bytes and the POH of the VC-11/VC-12 and VC-2 consists of 4 bytes.

*The RSOH is reformed (terminated) by each regenerator. Each regenerator section passes the MSOH transparently.*The MSOH is reformed (terminated) by each multiplexer and cross connect . *The Path Overhead is evaluated at the end point of the transmission system where the unpacking takes place.****Summary of the PDH/SDH multiplex procedure:

Container C-n: (n=1-4)Basic information structure which forms the synchronous payload. The input data rate is adapted by fixed stuffing bits. Clock deviations are compensated by a stuffing procedure similar to PDH.Virtual Container VC-n: (n=1-4)The virtual container is the information structure with facilities for maintenance and supervising. It comprises the information (payload) and the POH. Maintenance signals are path related which spans from end-to-end through the SDH system.Tributary Unit TU-n: (n=1-3); only for VC-1/2/3The tributary unit is formed of the virtual container and a pointer to indicate the start of the VC. The pointer position is fixed.Triburary Unit Group TUG-n: (n=3,4); only if TU's are available this is formed by a group of identical TUs for further processing.Administration Unit AU-n: (n=3,4)This element comprises a VC and an AU pointer. The pointer position is fixed within the STM-1 frame.*The Pointer indicates the phase shift of the first VC byte (J1, V5) within the payload or the container.For the mapping of 2Mbit/s signals into SDH, two pointer levels are used. The first level - the AU-4 pointer - identifies the start of the VC-4 reative to the basic STM-1 frame. The second level - the TU-12 pointers - identifies the start of the VC-12 relative to the VC-4 for each of the 63 VC-12s.The use of the pointer decouples the information channels (VC) from the transport medium (STM signal). The fixed phase relationships of older systems are avoided in this manner.It is also possible to multiplex and demultiplex signals in a single device across all levels. The byte position of a subsignal is easy to compute.*The actual pointer allocates 2 bytes, H1 and H2. The H3 bytes are allocated for negative justification (see next slide). The remaining 4 bytes have a fixed content (Y=11001 SS11, where S is unspecified).The pointer bytes H1, H2 consists of the following:NNNN (New Data Flag):normaly 0110. For pointer adjustments that are more than just increments or decrements, these 4 bits are inverted to 1001. This indicate that a completely new pointer value is to be used.SS:Indicate which AU is used. For AU-4/TU-3 the value is 10, for AU-3/TU-3 the value is 01.ID:This 10 bits carry the actual pointer value. The maximum legal value is 782 (decimal), even though the 10 bits can give a maximum value of 1023 d.I:5 bits in the pointer value. If a pointer increment has to take place, these 5 bits are inverted in the pointer bytes of one STM-1 frame. A majority vote is used to avoid the effects of bit errors. The pointer points out a 3-byte unit one position down in the SDH frame. The positive justification bytes following the pointer should be ignored. In the next frame the pointer has the new incremented value.*D:5 bits in the pointer value. If a pointer decrement has to take place, these 5 bits are inverted in the pointer bytes of one STM-1 frame. A majority vote is used to avoid the effects of bit errors. The pointer points out a 3-byte unit one position up in the SDH frame. The negative justification bytes following the pointer are used. In the next frame the pointer has the new decremented value.

*Mapping and Multiplexing:A 140Mbit/s PDH signal is mapped into the VC-4.The VC-4 consists of 261 columns, each consisting of 9 bytes. The actual start of the VC-4 is indicated by the AU-4 pointer. The first column is used for the POH. The remaining part of the VC-4 is used for the C-4 container.*The C-4 container can be considered as a 9 x 260 byte block. Each row is divided into 20 groups of 13 bytes. 12 of these bytes carry information bits (i.e. bits from the 140Mbit/s signal). The 13th byte is used for different purposes.

*If the SDH system is to carry 34Mbit/s PDH signals, they are mapped into a C-3 container. Together with the 9 byte POH we get the VC-3. The VC-3 is carried in the TUG-3 which can be considered as a 86-column block of data each column containing 9 bytes.The first column of the TUG-3 contains the pointer for the TU-3. The TU-3 pointer identifies the start of the VC-3 within the remaining 85 columns of the TUG-3. Legal values for the TU-3 pointer are 0 - 764.*Three 2 Mbit/s mapping methods are available:Asynchronous:The 2 Mbit/s signal is not synchronized to the SDH signal. This is the most common mapping available.Bit-synchronous: (not rec. any more)The rate of the 2 Mbit/s signal is synchronized to the SDH signal. The framing (if any) of the 2Mbit/s signal is not synchronized to the SDH signal. Byte-synchronous:Both, rate and framing of the 2 Mbit/s signal are synchronized to the SDH signal.

In addition two modes of operation are defined:Floating mode:The 2Mbit/s signal "floats" relative to the VC-4. The start of the signal is identified by a pointer.Locked mode:The 2 Mbit/s signal is locked to the VC-4. The start of the signal is fixed to the start of the VC-4. Pointers are not used.

*Mapping and Multiplexing:The SDH system permits the transport of various types of signals, in particular the existing PDH signals 140, 34 and 2Mbit/s. For each type of signal, mapping is defined. The mapping specifies how the space allocated for a signal is filled out. In addition it can compensate for frequency deviation between the PDH signal and the SDH system. This is handeled by justification, very similar to the justification mechanism employed in existing PDH systems. In the ETSI multiplex structure the SDH system will always use a VC-4 for transport of the PDH signals. If the SDH system carries a 140Mbit/s PDH signal, the signal is mapped directly into the VC-4. The VC-4 will be filled out completely by one 140Mbit/s signal and its overhead. Thus no SDH multiplexing occurs. If the SDH system carries 34Mbit/s or 2Mbit/s PDH signals , a number of these signals are multiplexed together into the VC-4. The basic unit to be multiplexed is called a Tributary Unit (TU). The multiplexed signals are called Tributary Unit Groups (TUG). TUGs are defined in two levels. The highest level are the TUG-3s. Three of these can be carried in a VC-4. A VC-4 can be considered as a block of data with 261 columns and 9bytes in every column. A TUG-3 is a block of data with 86 columns and 9 bytes in every column. The content of a TUG-3 may be a TU-3 which carries a 34Mbit/s PDH signal in a VC-3 or 7 TUG-2s. A TUG-3 carries a TU-3, the first 2 columns are allocated for a TU-3 pointer and for stuffing bytes. A TU-3 pointer will point out the start of a VC-3.

*Mapping and Multiplexing:A TUG-3 may instead carry 7 TUG-2s. TUG-2s will cary 3 TU-12s each if the system is used for 2Mbit/s signals. The way in which the TUG-2s and the TU-12s are multiplexed into the TUG-3 is illustrated above.When the TUG-3 carries TUG-2s the space allocated for TU-3 pointer contains a Null Pointer Indication (NPI). The remaining part of the TUG-3 is filled with the content of the TUG-2s and the TU-12s.*As indicated in the TU-12 structure before, four columns with 9 bytes each, are allocated for TU-12s per SDH frame. This gives 36 bytes per SDH frame i.e. 8000 times per second. The requirement for a 2Mbit/s PDH signal is 32 bytes 8000 times per second. This would indicate that the 2 Mbit/s frame would fit directly into the TU-12. However, for the mapping type explained here, the requirement for overhead and justification make it necessary to allocate more space per VC-12 than 4 additional bytes per SDH frame. This is achieved by concatenating the 36 bytes, allocated for a TU-12 in 4 consecutive VC-4s.As shown above, the first bytes of the 4 concatenated TUs contain the TU-12 pointer (V1-V4). The remaining 4 times 35 bytes should now be considered as one block of data capacity in which the VC-12 is placed. the actual start of the VC-12 is pointed out by the TU-12 pointer. The first byte of the VC-12 carries one byte of path overhead (V5). The remaining part of the VC-12 is the C-12. A C-12 carries nominally four 2Mbit/s PDH frames (each with 32 time slots).The first row (bytes 10 to 62) of the VC-4 contains the first byte of each TU-12.

*VC-4 Concatenation is used to carry broadband information via the SDH network. A total bandwith of appr. 600Mbyte/s is available within one concatenated Virtual Container (VC-4c).ATM is one of the main applications of STM-4c networks. These interfaces to ATM switches are used more and more frequently for internetworking.Two different methodes are used:VC-4 Contiguos ConcatenationVC-4 Virtual Concatenation**The switching capability of a nowadays used Crossconnect is limited to 150 Mbit/s. (VC-4) Operators of telecom equipment need this method in order to transmit concatenated VC-4 containers via their existing SDH networks. European telecoms must carry out pilot projekts and measurements for the new methods.**Here we see an rough overview of the differences between the SONET and the SDH systems.*The STS-1 frame is the lowest hierarchy of the SONET system and has a transmission speed of 51.840Mbit/s. The Transport Overhead (TOH) consists of the row 1, 4 and 7 of the STM-1 overhead of the SDH system.The STS-1 hierarchy is also known as STM-0 in the European countries and is used on radio links where not the total bandwith of a SDH system is required.***Add Drop Multiplexer This is the most common element to built up SDH rings. Dependent on the port configuration it gives access to all containers embedded in the STM-1 signals. These containers can be dropped and inserted in the SDH hierarchy. Each tributary can also be inserted into each container of the STM-1 streams. An ADM155 for example is a multiplexer, which handles 126 x 2Mbps tributaries within 2 independent STM-1 datastreams (doublering). Also the exchange of the containers between the STM-1 signals is possible. The ADMs are controlled via TMN commands in embedded channels or the via the Q-interface. It has a built in switching unit, which supports Automatic Protection Switching (APS) , if one line has interruptet. Only ANT-20 offers*Synchronous Cross Connect : Digital Cross Connects(DXCs) handle signals of PDH and/or SDH technologies. They offer several inputs for those bitrates which are present as port cards in a specific hardware configuration of this network element. Today its possible to apply signals up to STM-4, in the future 2.5Gbit/s will be possible. A cross connect extracts containers from all incoming signals. It can rout all incoming signals (or parts of them) to each outgoing signal, from one hierarcye to another, from SDH to PDH and vice versa. Normally switching takes place at the basic container levels (VC12, VC3, VC4). Some DXCs offer access down to 64kbps by the help of byte-synchronous mapping. DXCs are located at such places where several different signals are coming together, with different bitrates. It also interconnects local levels to long distance levels, e.g. ADM rings on SLX or PDH on SLX. Its controlled via workstations and TMN and handles also all alarms and status information of different hierarchies. A DXC requires fully structured signals (PDH 140/34/8/2Mbps) of the corresponding bitrate, otherwise it will generate alarms and measurements are more difficult or impossible. DXCs are very complex machines - therefore the goal of most operators is to minimize the amount of DXCs and to replace them by the more cheeper Add Drop multiplexers (ADMs) wherever it's possible. *Synchronous Line Equipement A synchronous line multiplexer multiplexes / demultiplexes several STM-1 signals into a STM-N datastream. Output is an optical signal with wavelength of 1310 or 1550 nm. The ANT-20 offers switchable 1310/1550 nm for STM-1 and -4 ports avoiding exchange of modules in analyser. Already today the ANT-20 offers the extension of STM-16. Its the only instrument on the market which can include all STM bitaretes up to STM-16 in one box ! Further NEs are : Termination Mutliplexres - convert PDH signals to SDH Regenerators - optical / electrical line regenerators ATM-equipement with PDH, SDH and SONET interfaces ****A special synchronization network is set up to ensure that all of the elements in the communications network are synchronous. The network is hierarchical distributed. A primary reference clock source (PRS) controls the secondary clocks of stratum level 2 to 4 (SSU or ST2 to 4). This type of synchronization signal distribution is also refered as Master/Slave synchronization. The actual synchronization may take place via a separate , exclusive sub-network, or the communications signals themselves may be utilized. Ring structures are also possible.

*The quality of the distributed clock is degraded in line with the number of intervening synchronization elements. Too many such elements impair short-term stability and lead to pointer processes. Their number is therefore restricted.

*Synchronization possibilities of SDH Network elements:The element clock is of Stratum level 3 or 4. If the incoming (higher quality) clock signals fail or are unsuitable for synchronization, the effected unit switches to hold-over mode (internal clock source)*If a network element is cut off from all external clock supplies, it switches tohold-over mode automatically. The internal oscillator serves as the clocksource, but is enhanced with the correction values from synchronizedoperation (accuracy 5 x 10-8 at a constant temperature in accordance withG.813). Hold-over mode is not intended as a permanent operating mode.It merely serves to maintain network operation (with degraded quality)until the cause of the disturbance has been removed.

*The manner in which the phase of the internal clock oscillator slowly driftsaway on account of the frequency offset is clearly visible.

53***Here we see a comparison between SDH and SONET events.As known already, SDH (SONET) provides a high number of Anomaly and Defect indication. This hierarchical system provides the possibility to allocate the point of a problem in the network very easy.*The SDH system monitors transmission quality using a method called Bit Interleaved Parity (BIP).A number of BIP types are used in SDH:BIP-24 for B2 bytes is formed for every STM-1 frame w.o. RSOH.BIP-8 for B1 byte for STM-N frame after scrambling and for B3 byte for the VC-3 and VC-4.BIP-2 for the V5 byte for VC-11, VC-12 and VC-2. **On the transmit side a code word is formed using a fixed encoding rule for a specific bit stream within the STM module. The code word is transmitted in the parity bytes of the following module. The same rule is used to compute an identical word on the receive end. This code word is compared with the incoming code word in the B bytes of the next module. Mismatch indicates transmission error(s).

*The procedure for calculating the BIP-n is:A relevant number of bits are received (e.g. the total number of bits in an STM-1 frame).These bits are grouped into n columns (e.g.24 for BIP-24).For each column the parity is calculated. The parity is even (or 0) if there is an even number of 1s in the column; the parity is odd (or 1) if there is an odd number of 1s in the column.The related bit in the BIP-n is set to the parity of the column.*In this picture we see the interaction of the maintenance signals. Please try yourself how a SDH network element should react in the right way.*To help you a little bit to understand the maintenance signals here is the explaination whats behind.**Performance of a transmission system is a very important factor. G.821 is defined for a 64 kbit/s channel and therefor not very useful for the SDH hierarchies.G.826 is a block based performance analyses and not limited to the 64 kbit/s level. G.826 uses the parity bytes B1, B2, B3 and V5 for evaluating the performance characteristic.**Jitter:Periodic or random changes in the phase of the transmission clock referred to the master or reference clock. In other words, the edges of a digital signal are advanced or retarded in time when compared with the reference clock or an absolutely regular time framework. Jitter generally referes to deviations of more than 10Hz.

Wander:Slow changes in phase (below 10Hz); a special type of jitter.*Interference signalsImpulsive noise or cross talk may cause phase variations (non systematic jitter). Normally high frequency jitter.Pattern dependent jitterDistortion of the signal lead to so-called inter-symbol interference, which is pulse cross talk that varies with time (Pattern dependent jitter.Phase noiseThe clock regenerators in SDH systems are generally synchronized to a reference clock. Some phase variations remain, due to thermal noise or drift in the oscillator used.Delay variationChanges in the signal delay times in the transmission path lead to corresponding phase variations. These variations are generally slow (Wander). (e.g. Temperature changes in optical fibers).Stuffing and wait time jitterDuring removing of stuffing bits gaps have to be compensated out by a smoothed clock.Mapping jittersee abovePointer jitterDuring incrementing or decrementing of the pointer value. This shifts the payload by 8 or 24 bits corresponding to a phase hit of 8 or 24 UI.*A jitter meter test set is basically made up from the following items:Pattern clock converter reference clock generator phase meter weighting filters peak value detector*To avoid communication problems, the jitter at the outputs of network elements in a digital network must not exceed certain limit values. The values are nominally specified:High-frequency jitter and combined jitter. The requirements for SDH network interfaces are specified in ITU-T Rec. G.825*Measure of jitter amplitude in Unit Interval [UI].1UI corresponds to an amplitude of one bit clock period. The unit interval UI is independent of bit rate and signal coding as it is referred to the length of a clock period. The peak to peak value is expressed in UIpp.**International standards define upper limits for MTIE and TDEV.

A rough assesment of the tributary wander that may occure can be made by observing the pointer in an SDH system. If no pointer jumps are seen, this means that no wander occured during the period of observation. If pointer jumps occure, the wander values can be accessed as follows:For example, a pointer jump in the AU level at STM-1 corresponds to 3x8 bits at 155 Mbit/s. This means that the drift is 156 ns referred to the payload of 140 Mbit/s.*TIE:Measure of the time deviation in a clock signal relative to the reference clock refered to an observation interval.

MTIE:Is defined as the maximum deviation in time (peak-to-peak value) of a clock signal in relation to a reference clock within a specified observation interval.*It is importand to know, if the measured wander events are within the limits specified from ITU-T, ETSI or ANSI. Therefore modern test eqipment provide the possibility to compare the recalculated MTIE or TDEV values against different clock accuracy standards:

ITU-TANSI / Bellcore ETSI Definitions G.810T1.101 / GR-253ETS 300 462-1Network G.825T1.105 / GR-253ETS 300 462-3Primary Reference Clocks G.811T1.101ETS 300 462-6Synchron. Supply Clocks G.812T1.101TS 300 462-4Equipment Clocks G.813 (G.81s)GR-253ETS 300 462-5

**1+1 ConfigurationThe simplest form of back-up is known as 1 + 1 APS. Here, each working line is protected by one protection line. The same signal is transmitted on both lines. If a failure or degradation occurs, the network elements switch the connection over to the protection line at the receive end.

1:1 ConfigurationAnother approach is the 1 :1 configuration. A protection line is used to directly replace the working line when it fails.The protection path can only be used if a switchover takes place at both the transmitting end and the receiving end. Switching at the far end is initiated by a return message in the backward channel.

1:N ConfigurationA 1:N configuration represents a more cost-effective solution than the other two mechanisms described above. N working channels are protected by one protection channel. If there are no defects in the network, this protection channel can be used to transport low-priority traffic.

**Unidirectional path switching Two unidirectional rings - Performance of each signal is monitored in its POH- Each fiber carries full bandwidth- Simple protection algorithm : automatic switchover to RX signal from other ring- No knowledge ogf ring configuration is needed- Restoration time less than 50ms

*Unidirectional line switching Two unidirectional or bidirectional rings - Performance is monitored using the MSOH (LOH) - Working fiber carries full bandwidth- Line B E traverses the entire ring - Detection of line failure initiates exchange of messages among nodes - Line protection switching APS - All traffic is restored - It's not initiated by path degradation- Knowledge of ring configuration is needed- Restoration time less than 50ms

*Two fiber bidirectional line switching Each fiber carries working and protection channels - 50% working, 50% protection channels- Performance is monitored using the MSOH (LOH) on all spans (span lines between 2 beneeth nodes) - Working fiber carries full bandwidth - Detection of line failure initiates exchange of messages among nodes - Line protection switching APS - All traffic is restored - It's not initiated by path degradation- Knowledge of ring configuration is needed- Restoration time less than 50ms

*Four fiber bidirectional line switching Two fibers carry working channels (duplex)two fibers carry protection channels

- Performance is monitored using the MSOH (LOH) of all spans (span lines between 2 beneeth nodes) - Working fiber carries full bandwidth - Detection of line failure initiates exchange of messages among nodes - Line protection switching APS - All traffic is restored - It's not initiated by path degradation- Knowledge of ring configuration is needed- Restoration time less than 50ms

*Four fiber bidirectional span switching Two fibers carry working channels (duplex)two fibers carry protection channels

- Performance is monitored using the MSOH (LOH) of all spans - Working fiber carries full bandwidth - Failure is only affecting working channels- Traffic is switched to protection path- Failure does not affect other spans- All traffic is restored - It's not initiated by path degradation- Knowledge of ring configuration is needed- Restoration time less than 50ms

******To operate a telecommunications network economically, network management must be optimized. Any technical problems within the management network may result in a loss of revenue. To keep these losses as low as possible, these problems must be solved quickly. Most of these problems (interoperability problems) can be identified by analyzing the data exchanged between the communication entities of the TMN.Interoperability problems within the TMN are mostly due to faults or inconsistencies in the protocols and information models. The QMonitor is the right tool for localizing and analyzing such problems.The QMonitor decodes the protocols on all 7 layers of the Q3 interface and the management information, so that the problem can quickly be located. With the next QMonitor version (available in first quarter 97) errors in the management information (e.g. not allowed operation on a managed object) can be detected automatically.The protocol stacks can be individually (auto)configured to exactly match the stack configurations of the system under test.In order to analyse the protocols and management information in the SDH embedded control channel (Qecc) the QMonitor can be linked to transmission analyzers (e.g. ANT-20), which provide the Qecc bit stream at an interface supported by DA-30 or Dominos.

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Basics on SDH and PDH