1 1 1 Rev 2010-08-10 R1A Introduction to Transmission Systems
Nov 18, 2015
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11 Rev 2010-08-10
R1A
Introduction to Transmission Systems
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201-2 Intro to Transmission Systems
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PDH (Plesiochronous Digital Hierarchy)
PDH is a technology used in telecommunications networks to transport large quantities of data over
digital transport equipment.
The term plesio-chronous refers to the fact that PDH networks run in a state where different parts of the
network are nearly, but not quite perfectly, synchronized.
Difference in clock between PDH elements is compensated by signalling between the Tx and Rx to
indicate missing bits.
The transmitting multiplexer adds additional bits to allow the far end receiving multiplexer to decode
which bits belong to which 2-Meg data stream. These additional bits are called "justification" or "stuffing"
bits.
The basic unit in PDH is called the E0 and has a rate of 64Kbps.
There are two different PDH systems, European and American systems.
139264 KbpsE4
34368 KbpsE3
8448 KbpsE2
2048 KbpsE1
64 KbpsE0
Data RateNotation
139264 KbpsT4/DS4
44736 KbpsT3/DS3
6312 KbpsT2/DS2
1544 KbpsT1/DS1
64 KbpsT0/DS0
Data RateNotation
European Standard
(30 E0 + 2 E0 for signalling)
American Standard
(24 E0 + framing bits)
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PDH Limitations
No world standard on digital format. Making equipment to convertdifferent standards is costly.
No world standard for optical interfaces. Networking is impossible at the optical level.
Rigid asynchronous multiplexing structure. No direct multiplexing.
Limited management capability.
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401-2 Intro to Transmission Systems
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SDH (Synchronous Digital Hierarchy)
International Telecommunication Union ITU standard
First set of SDH recommendations released in 1988
A flexible and efficient method to convey digital information from one designated location to another
An international standard for high-speed optical and electrical telecommunications networks
Solution for data-transmission in broadband telecommunications network
SDH
Transport
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Advantages of SDH
Direct mapping (transport) of PDH (TDM), ATM and IP signals
Effective and powerful multiplexing, de-multiplexing and cross connecting
Standardised NNI for both optical and electrical interfaces
Dynamic network protection in ring topology (self healing)
In service supervision and management for all Network Elements (NE)
Centralised network control and timing recourses
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601-2 Intro to Transmission Systems
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Components and topology
Network elements
DXC - Digital Cross ConnectADM - Add/Drop Multiplexer
TM - Terminal MultiplexerRT - Radio Terminal
RR - Radio RepeaterOR - Optical Repeater
Typical Capacity
Access network: PDH, STM-0, STM-1Regional network: STM-1, STM-4, STM-16
National network: STM-16, STM-64
ADM
ADMADM
Regionalnetwork(Ring)
Access network(Chain)
RT RTRR
RTRT
National network(Mesh)
DXC
DXCRTDXC OR RT
ORDXC OR
TM
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The SDH frame
Frame header + Payload = Synchronous Transport Module (STM)
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801-2 Intro to Transmission Systems
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MSOH
AU - pointers
STM STM --1 payload1 payload
RSOH
261 bytes
270 bytes
9 bytes
3 rows
5 rows
1 row
STM - 1 bit rate:
8000 frames/sec x 9 rows/frame x 270 bytes/row x 8 bits/byte = 155.520 Mb/s
STM-1 Frame Structure
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MSOH
AU - pointers
STM STM --n payloadn payload
RSOH
nx261 bytes
nx270 bytes
nx9 bytes
3 rows
5 rows
1 row
STM - n bit rate:
nx8000 frames/sec x 9 rows/frame x 270 bytes/row x 8 bits/byte = nx155.520 Mb/s
STM-n Frame Structure
40 Gbps39813.12 MbpsSTM-256
10 Gbps9953.280 MbpsSTM-64
2.4 Gbps2488.320 MbpsSTM-16
622 Mbps622.080 MbpsSTM- 4
155 Mbps155.52 MbpsSTM-1
51 Mbps51.84 MbpsSTM-0
AKABit RateSignal name
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1001-2 Intro to Transmission Systems
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Section Layers
MST - Multiplexer Section Termination (DXC, ADM, TM)
RST - Regenerator Section Termination (RT, RR, OR)MS - Multiplexer Section
RS - Regenerator Section
RSTMSTMSTMST
RST RST RSTRST
RS RSRS RS
MS
RSRSRS
MS
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RSTMSTMSTMST
RST RST RSTRST
RS RSRS RS
MS
RSRSRS
MS
Path layer
Higher order pathVC-3 (34 Mb/s)
VC-4 (140 Mb/s)
Mapped ATM / IP
Path Layers
Lower order path VC-12 (2Mb/s)
Mapped ATM / IP
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1201-2 Intro to Transmission Systems
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SDH Multiplexing Structure
Pointer
Processing
Multiplexing
Mapping
C-nx : Container
VC.nx : Virtual Container
TU-nx :Tributary UnitAU-n : Administrative Unit
TUG-n : Tributary Unit Group
STM-N : Synchronous Transport Module
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VC-12 Mapping Structure
C-12Container for 2.048 Mb/s C - 12
C-12VC - 12 POH VC - 12
POH C-12TU - pointer TU - 12
TU - 12TU - 12TU - 12Byte interleave 3 x TU - 12 TUG - 2
Byte interleave 7 x TUG - 2
TUG - 3
Byte interleave 3 x TUG - 3
TU - 12TU - 12
TU - 12TU - 12TU - 12
TU - 12
TU - 12
TU - 12TU - 12TU - 12
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TU - 12
C-4
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VC - 4 POH VC - 4
RSOH
STM - 1
TU - 12TU - 12
TU - 12TU - 12TU - 12
TU - 12
TU - 12
TU - 12TU - 12TU - 12
TU - 12
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H
AU - PointerAU - 4
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HAU-Pointer
TU - 12TU - 12
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J0A 2AAA 1A 1A 1 A2 A2 A
B 1 E 1 F1 N N
D1 D 2 D3
H 2 H2 H 2 H3 H3 H3H1
B 2 B 2 B 2 K 1 K2
D4 D 5 D6
D7
D10
S1 Z 1 Z1 Z 2 Z2 M1 E2 N
D9
D1 2
D 8
D 11
N
H1
A 1A 1
H1
A 1
MS 2
SI
#1 #2 #3
N
MS 3
MS 1
NV
C-4
PO
H
MSOH
VC-12 Mapping Structure
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1501-2 Intro to Transmission Systems
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VC-4 structure: Can be used to map 150Mb/s
Ethernet traffic.
Mixed TU-12/TU-3 structure: Each TU-12 can be
used to map approx. 2Mb/s Ethernet traffic or E1
traffic. Each TU-3 can be used to map approx.
50Mb/s Ethernet traffic or E3/DS3 traffic.
TU-3 structure: Each TU-3 can be used to map
approx. 50Mb/s Ethernet traffic or E3/DS3 traffic.
TU-12 structure: Each TU-12 can be used to map
approx. 2Mb/s Ethernet traffic or E1 traffic.
STM-1 Structure Examples
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J0A2AAA1A1A1 A2 A2 A
B1 E1 F1 N N
D1 D2 D3
H2 H2 H2 H3 H3 H3H1
B2 B2 B2 K1 K2
D4 D5 D6
D7
D10
S1 Z1 Z1 Z2 Z2 M1 E2 N
D9
D12
D8
D11
N
STM-1RSOH
POINTER
STM-1MSOH
H1
A1A1
H1
A1MS
2Mb/s
Media Specificbytes
2 Mb/s asynchronous
.
MS 2
SI
#1 #2 #3
N
MS 3
MS 1
SI : Stuffing for 2Mb/s Wayside
MS 1&2 : Radio Protection Switching control
MS 3 : RF-IdRemote reset
ATPCE/M for bytes; E1, F1, E2
N
SOH - Section Overhead
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1701-2 Intro to Transmission Systems
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A1/A2 - STM -1 frameword. (A1: 11110110, A2: 00101000)
J0 - Regenerator section trace
B1 - Regenerator section error calculation (BIP-8)
E1 - Regenerator Orderwire
F1 - Regenerator User channel
D1/D2/D3 - Data Communication Regenerators (192Kb/s)
NU - National Use
MS - Media Specific bytes
UN - UNallocated bytes
A1 A1 A1 A2 A2 A2 J0 NU NU
B1 MS MS E1 UN UN F1 NU NU
D1 MS UN D2 UN UN D3 UN UN
RSOH - Byte Description
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1801-2 Intro to Transmission Systems
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B2 - Multiplexer section error calculation (BIP-24)
K1/K2 - Multiplexer protection switching
D4-D12 - Data Communication Channel multiplexer (576Kb/s)
Z1/Z2 - Reserved for future use
E2 - Multiplexer Orderwire
S1 - Syncronization status
M1 - Multiplex Section - Remote Error Identifier (MS-REI)
NU - National Use
UN - UNallocated bytes
B2 B2 B2 K1 UN UN K2 UN UN
D4 UN UN D5 UN UN D6 UN UN
D7 UN UN D8 UN UN D9 UN UN
D10 UN UN D11 UN UN D12 UN UN
S1 Z1 Z1 Z2 Z2 M1 E2 NU NU
MSOH - Byte Description