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*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
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*The World of Synchronous Networks*Current Transmission
Technologies
The World of Synchronous Networks
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*The World of Synchronous Networks*The Telephone SystemLELE
The World of Synchronous Networks
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*The World of Synchronous Networks*Audio SignalSampler
OutputPulse Amplitude Modulated (PAM) signalSampling
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*8 bits per
samplex=64kbit/s8000 samples per secPCM Signal Data Rate
The World of Synchronous Networks
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*The World of Synchronous Networks*Time Division Multiplexing
(TDM)
The World of Synchronous Networks
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*The World of Synchronous Networks*PDH Systems Worldwide
The World of Synchronous Networks
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*The World of Synchronous
Networks*AISPDHEquipmentAISPDHEquipmentLOSLOFAISD-BitBER
10-3D-BitBER 10-6N-BitPDH Maintenance Signals
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*The Synchronous Digital
Hierarchy (SDH)
The World of Synchronous Networks
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*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
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*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
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*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
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*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
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*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
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*The World of Synchronous Networks*Bit Rates, Frame Structure
and Interfaces in SDH
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*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
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*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
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*The World of Synchronous Networks*C-4STM-1 Frame Structure
The World of Synchronous Networks
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*The World of Synchronous Networks*VC-4C-4VC-4 POHSTM-1 Frame
Structure
The World of Synchronous Networks
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*The World of Synchronous Networks*AU PointerAU-4VC-4C-4VC-4
POHSTM-1 Frame Structure
The World of Synchronous Networks
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*The World of Synchronous Networks*13594270270 Columns
(Bytes)19RSOHMSOHAU PointerSTM-1 Frame Structure
The World of Synchronous Networks
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*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
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*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
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*The World of Synchronous Networks*Basic Elements of STM-1
The World of Synchronous Networks
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*The World of Synchronous Networks*Overhead Byte
Functionality
The World of Synchronous Networks
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*The World of Synchronous Networks*RSOHMSOHAU
pointerVC-4TUG-3TUG-2TU-12VC-12Tu pointerMapping 2 Mbit/s
The World of Synchronous Networks
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*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
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*The World of Synchronous Networks*SDH Network Elements
The World of Synchronous Networks
- *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
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*The World of Synchronous Networks*Synchronous Cross Connect
The World of Synchronous Networks
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*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
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*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
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*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
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*The World of Synchronous Networks*Synchronization Architecture
in SDH
The World of Synchronous Networks
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*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
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*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
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*The World of Synchronous Networks*Synchronization of SDH
Network ElementsSynchronousSDH SignalSDH Network Element
The World of Synchronous Networks
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*The World of Synchronous Networks*Phase error [ ns]Observation
interval [s]0.0111001000010100100010000100000Hold-over mode
The World of Synchronous Networks
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*The World of Synchronous Networks*Hold-over measured values
(TIE)
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*Monitoring, Maintenance and
Control Functions in SDH
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*Frame Areas Covered by Parity
BytesRSOHMSOHPayloadB1:- Supervision of the whole STM-1 frame-
Covers the regenerator sections of a trans- mission 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
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*The World of Synchronous Networks*Parity Supervison
ProcedureTransmit Side
The World of Synchronous Networks
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*The World of Synchronous Networks*Parity Supervison
ProcedureTransmit SideB1Receive Sideframe n+1frame nrecalculation
at Rx side
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*SDH MAINTENANCE
INTERACTIONS
The World of Synchronous Networks
-
*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
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*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
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*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
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*The World of Synchronous Networks*Jitter and Wander
The World of Synchronous Networks
-
*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
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*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
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*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
-
*The World of Synchronous Networks*Max. Jitter
Amplitude:1,5UI0,15UIJitter Measurement Filters
The World of Synchronous Networks
-
*The World of Synchronous Networks*Jitter Amplitude
(PP)Measurement PeriodJitter / UIppTimeDefinition of Jitter
Peak-to-Peak Amplitude
The World of Synchronous Networks
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*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
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*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
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*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
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*The World of Synchronous Networks*Results (MTIE) compared to
Standards
The World of Synchronous Networks
-
*The World of Synchronous Networks*Network resilience
The World of Synchronous Networks
-
*The World of Synchronous Networks*Linear Protection
(G.783)WPWPWWP1 + 1 Protection scheme1 : 1 Protection scheme1 : N
Protection scheme
The World of Synchronous Networks
-
*The World of Synchronous Networks*Linear Protection
(G.783)WPWPWWP1 + 1 Protection scheme1 : 1 Protection scheme1 : N
Protection scheme
The World of Synchronous Networks
-
*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
-
*The World of Synchronous Networks*Unidirectional Path-Switched
RingTributaryTributaryACBFDEFiber 2 : unidirectionalFiber 1 :
unidirectional
The World of Synchronous Networks
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*The World of Synchronous Networks*Unidirectional Path-Switched
Ring
The World of Synchronous Networks
-
*The World of Synchronous Networks*Unidirectional Path-Switched
RingTributaryTributaryACBFDEFiber 2 : unidirectionalFiber 1 :
unidirectional
The World of Synchronous Networks
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*The World of Synchronous Networks*Unidirectional Line-Switched
RingTributaryTributaryACBFDEProtectionWorkingWorking
The World of Synchronous Networks
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*The World of Synchronous Networks*Unidirectional Line-Switched
RingTributaryTributaryACBFDEProtectionWorkingWorking
The World of Synchronous Networks
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*The World of Synchronous Networks*Unidirectional Line-Switched
RingTributaryTributaryACBFDEProtectionWorkingWorking
The World of Synchronous Networks
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*The World of Synchronous Networks*Two fiber Bidirectional
Line-Switched Ring (BLSR)workingprotection
The World of Synchronous Networks
-
*The World of Synchronous Networks*Two fiber Bidirectional
Line-Switched Ring (BLSR)workingprotection
The World of Synchronous Networks
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*The World of Synchronous Networks*Two fiber Bidirectional
Line-Switched Ring (BLSR)TributaryABFCDE TributaryFiber 1Fiber
2workingprotection
The World of Synchronous Networks
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*The World of Synchronous Networks*Four fiber Bidirectional
Line-Switched Ring (BLSR)
The World of Synchronous Networks
-
*The World of Synchronous Networks*Four fiber Bidirectional
Line-Switched Ring (BLSR)
The World of Synchronous Networks
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*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
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*The World of Synchronous Networks*Four fiber Bidirectional
Span-Switched RingTributaryABFCDE TributaryProt.Fiber 3 + 4Working
Fiber 1 + 2
The World of Synchronous Networks
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*The World of Synchronous Networks*Four fiber Bidirectional
Span-Switched RingTributaryABFCDE TributaryProt.Fiber 3 + 4Working
Fiber 1 + 2
The World of Synchronous Networks
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*The World of Synchronous Networks*Four fiber Bidirectional
Span-Switched RingTributaryABFCDE TributaryProt.Fiber 3 + 4Working
Fiber 1 + 2
The World of Synchronous Networks
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*The World of Synchronous Networks*TMN in SDH networks
The World of Synchronous 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
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*The World of Synchronous Networks*TMN Overlay
The World of Synchronous Networks
-
*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
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*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
-
*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
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*The World of Synchronous Networks*SDH Benefits
The World of Synchronous Networks
-
*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
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*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
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*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
-
*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
-
*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
-
*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
-
*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 ?
The World of Synchronous Networks
*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.
****