3 - intro sdh
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OVERVIEW OF THE SYNCHRONOUS DIGITALHIERARCHY
( SDH )
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
A BRIEF HISTORY
- 1983 : BELLCORE proposal and standardization of a 45 Mbit/s synchronous frame
(SYNTRAN system) providing direct access to the 64 kbit/s channel
- at the same time,AT&T develops a synchronous system (METROBUS) at 146 Mbit/s.
- 1985 : BELLCORE begins research into a "Synchronous Optical Network " project.
"SONET will be the basis of work at the CCITT.
- 1986 : CCITT committee set up on the subject.
- 1988 : first CCITT Recommendations are published (G.707 to G.709).
- 1990 : ETSI chooses multiplexing as the way forward.
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PDH VERSUS SDH
PDH SDH
PDifferent standards between US and rest of
world. No standard above 565 Mbit/sPWorldwide CCITT standard, three
standard rates:
155 Mbit/s, 622 Mbit/s, 2.5 Gbit/s, 10 Gbit/s
PManufacturer-specific administration PStandardization of TMN under way (info
model)
PAccess to basic channels at the cost of
numerous multiplexing/demultiplexing stagesPSimplified access to basic channels by the
system of A.U. and A.D.M. (Add and Drop
Multiplexors)
PService modification long and costly PReconfiguration on request by T.M.N.
PRuggedness and rerouting of data
expensivePNew network structures (loop) with
inherent protection
PKnowledge of quality in "portions" PKnowledge of quality from end to end
OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
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STM-N AU-4AUG VC-4
TUG-3
TUG-2
TU-12
TU-2
TU-3 VC-3
VC-2
VC-12
VC-11 C-11
C-12
C-4
AU-3 VC-3 C-3
TU-11
139.264 Mbit/s
44.736 Mbit/s
34.368 Mbit/s
C-2 6.312 Mbit/s
2.048 Mbit/s
1.544 Mbit/s
xN x1
x3
x7
x4
x7
x1
x1
x3
x3
STM-N FRAME MULTIPLEXING STRUCTURE
Multiplexing
Pointer processing
Alignment
Mapping
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STRUCTURE OF THE STM-1 FRAME
1
RSOH
PAYLOAD
MSOH
9
1 9 10 270
R OH: Regenerator ection Overhead
OH: ultiplex ection Overhead
Frame length: 2430 bytes
Frame frequency: 8 kHz
Bit rate: 155.520 bit/s
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
A1 A1 A1 A2 A2 A2 J0
1 E1¡
1
D1 D2 D3
AU P¢
INTE£
S
2
2
2 K1 K2
D4 D5 D6
D7 D8 D9
D10 D11 D12
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YTES£
ESE£
VE D¡
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E INTE£
NATI ¢ NAL STANDA£
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NATI¢
NAL USE
MEDIA DEPENDENT
YTES
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raming
D 1, D12 D at a co mm un icat io n ch an nel
J0 (o r C1) M odule identi ¤ ier
E1,E2 ¢ rderwire¡
1 User channel
1
IP-8 (regenerator section quality)
2
IP-24 (multiplex section quality)
K1,K2 APS channel
Z1,Z2 Spare
S1 Synchronization state
M1 "¡
E
E section"
SOH STRUCTURE(ITU-T G.708)
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
A1 A1 A1 A2 A2 A2 J0
¥
1 E1¦
1
D1 D2 D3
AU P§
INTE ̈
S
¥
2¥
2¥
2 K1 K2
D4 D5 D6
D7 D8 D9
D10 D11 D12
S1 Z1 Z1 Z2 Z2 M1 E2
¥
YTES ̈
ESE ̈
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IT/S, JUSTI¦
IED
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raming
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ier
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2
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E section"
SOH STRUCTURE(ETSI proposal TM4, not ITU-T compliant)
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
RADIO SYSTEM FRAME ( STM-1 )1
RSOH
PAYLOAD
MSOH
9
1 9 10 270
S : egenerator Section verheadMS : Multiplex Section verhead
Lenght rame: 2430 octets
rame requency: 8 K z
it rate: 155.520 Mbit/s
2Mbit/S Way Side Tra ic
Speci ic bytes or A96xxUSY(ATPC,MC,DSI)+ E1, 1,D1-D2-D3
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
PR INCIPLES OF MULTIPLEXING IN SDH
- mapping of t e plesioc ronous tri utary into a container using padding and justification its: conventional
plesioc ronous multiple ing.
- addition of t e corresponding PO H (creation of t e virtual container )
- t e virtual container is t e asic element in SDH
- alignment of t e virtual containers in t e tri utary units y positive-zero-negative justification. The C floats
ithin the TU. Its position is indicated on each frame y pointers .
- identical alignment y pointers is used to form the AU.
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
Terminology:
AU-n Administrative Unit,level n (= VC-n PT for high order containers
AUG Adminitrative Unit Group (group of AU-n)
C-n Container, level n
TU-n Tributary Unit, level n (=VC-n PT for basic containers)
TUG Tributary Unit Group (group of TU-n)
VC-n Virtual Container, level n (=C-n POH)
Bit rate (kbit/s) for networks in which the hierarchy is based on a
primary rate of
Digital hierarchy level G702 1544kbit/s 2048kbit/s
1 1544 20482 6312 8448
3 44736 34368
4 97728 139264
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PT
1
2
N
STM-N
PT
PT
P
P
VC-4VC-3ouVC-12
MULTIPLEXING ITH TWO LEVELS OF POINTERS
PT
PT: P INTE
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OVERVIEW OF THE SYNCHRONOUS DIGITAL HIERARCHY
SPI R ST ST SA SPIR STST
SOME FUNCTIONAL BLOCKS FROM RECOMMENDATION G.782
SPI (Synchronous Physical Interface)
RST (Regenerator Section Termination): Starts and ends the RSOH
MST (Multiplex Section Termination): Starts and ends the MSOH
MSA (Multiplex Section Adaptation): AU3/4 pointer processing
SEMF MCF
SETS SETPI
Q interfaceF interface
external synchronization
SEMF (Synchronous Equipment Management Function): converts supervision data into object-oriented
messages
MCF (Message Communication Function): provides the means of conveying TMN messages
SETS (Synchronous Equipment Timing Source): represents the frequency standard for the network
element
SETPI (Synchronous Equipment Timing Physical Interface): physical interface with the external clock