3. Author(s): Samadhan Ravindra Tambe
Date written (MM/DD/YY): 11/29/11
Project Details: SDH Transmission Related
PPT
4. What we will come to know after this presentation???
1. What is SDH.
2. Basic Frame structure of SDH.
3. How to calculate Basic Data Rate of SDH Frame using Total No. of Bits.
4. SDH Frame formation processes Mapping, Aligning, Pointer Processing etc.
5. SDH Frame formation using Lower Level Signal (C12).
Points Covered
5. What is SDH?
SDH Means Synchronous Digital Hierarchy, It is a standard Protocol for transmission of data over a
medium.
It is designed by International Telecommunication Union i.e. ITU and it was deployed on
telecommunication network in the year of 1992.
Main fundamental of SDH is to overly and transmit a Synchronous Multiplexed light stream Signal onto a
Fiber Optic cable.
SDH is bandwidth Flexible and it also allows Multivendor Internetworking. It has numerous advantages
over traditional Transmission technologies such as PDH i.e. Plesiocronous Digital Hierarchy (PDH).
SDH signal is bandwidth Flexible and hence different types of lower order signal can be transmitted in
its Virtual Container.
Introduction to SDH
6. Basic SDH Signal
The basic transmission format of SDH is a STM-1 Frame which is transmitted in 125 Microseconds time
slot in Byte wise pattern. There are 8000 Frames Transmitted per Second.
In all there are 9 Rows and 270 Columns in a STM Frame, of which first 9 Columns of each frame forms
Sectional Overheads and Pointer.
Remaining 261 Columns consist of Virtual Container (VC) which carries actual data. This VC along with
Pointer Bytes called as Administrative Unit (AU).
As there are 270 Columns, 9 Rows having 8 Bytes total number of bytes in STM-1 Frame will be
270*9=2430 Bytes.
Basic Facts About SDH
8. RSOH
Pointer
MSOH
Payload(VC)
P
O
H
270 Columns
261 Columns9 Columns
5Rows1Row3Rows
Hence Total No. of Bits = 270 Columns * 9 Rows * 8 Bits = 19440 Bits
Whole Frame transmitted in 125 microseconds
Thus Basic Data Rate of STM Frame is = 19440/125 µs = 155.52Mbits/sec
Now we will Calculate Basic SDH Data Rate by using total no. of bits…!!!
Data Rate of SDH Frame
9. Mapping
Adding justification bits and Path Overhead to Lower Level Signals so that they can be fit into Virtual
Containers (VC’s)
Vertual Container
Stuffing Bits
Stuffi
ng
Bits
Stuffing Bits
Stuffing Bits
Stuffi
ng
Bits
Stuffing Bits
Data Bits
Frame Formation Process
10. Aligning
Process of arranging the Virtual container so that pointer can be added.
Virtual Container
Virtual Container
Virtual Container
P
O
I
N
T
E
R
A
D
D
I
T
I
O
N
Frame Formation Process- Continued
12. Multiplexing
Process of combining Same size Units together.
Trib Unit
Trib UnitTrib Unit
Trib Unit
Frame Formation Process- Continued
13. SDH Digital Bit Rate Size of VC
VC-11 1.728 Mbit/s 9 rows, 3 columns
VC-12 2.304 Mbit/s 9 rows, 4 columns
VC-2 6.912 Mbit/s 9 rows, 12 columns
VC-3 48.960 Mbit/s 9 rows, 85 columns
VC-4 150.336 Mbit/s 9 rows, 261 columns
Table showing Virtual Containers (VC’s) Size
Formation of SDH Frame using VC12 is explained in next slide
Payload Container Sizes
14. C12VC12TU12
Signal is
mapped into
Container
VC’s are
aligned for
Pointer
Addition
TU12
TU12
TUG2
Pointer Processing
Tributary Units are
Multiplexed
TU12
TU12
TU12
TUG 3
This Slide will explain How Tributary Unit Group3 (TUG 3) is
formed from C12 ie. Lower Level Signal
7 TUG2’s are Multiplex to form TUG3
Formation Of TUG 3
15. VC4
3 TUG3 are Multiplexed together and placed in Higher order container VC4…!!!
AU4AUG1
VC4 is aligned for Pointer Processing
Administrative Unit Group Formation
16. Payload
Pointer, RSOH & MSOH Added to Auxiliary Unit Group(AUG1) and STM 1 Frame is formed
POINTER
MSOH
RSOH
H
O
P
O
H
STM Frame
A Complete SDH Frame- STM1
17. In Similar Way we can form SDH frame from different Lower level signals as follows
AU4
Pointer
Processing
Multiplexing
Aligning
Mapping
STM-N AUG AU4 VC4
TUG3 TU3 VC3
TUG2 TU2 VC2 C2
TU12 VC12 C12
TU11 VC11 C11
C4
AU3 VC3 C3
139 Mb/s
45 Mb/s
34 Mb/s
63 Mb/s
2 Mb/s
1.55 Mb/s
3
3
3
4
7
´7
Frame formation with other Signals
SDH Frame structure Consist of Rows and Columns.
SDH Frame transmitted in Byte wise pattern in just 125µs from top left corner till bottom right corner.
At start of each frame we have Framing Bytes (A1,A2) which indicates start of frame.
Bit Rate Abbreviated SDH SDH Capacity
51.84 Mbit/s 51 Mbit/s STM-0 21 E1
155.52 Mbit/s 155 Mbit/s STM-1 63 E1 or 1 E4
622.08 Mbit/s 622 Mbit/s STM-4 252 E1 or 4 E4
2488.32 Mbit/s 2.4 Gbit/s STM-16 1008 E1 or 16 E4
9953.28 Mbit/s 10 Gbit/s STM-64 4032 E1 or 64 E4
39813.12 Mbit/s 40 Gbit/s STM-256 16128 E1 or 256 E4
STM = Synchronous Transport Module
In the payload of SDH frame Data bits mapped into payload container and some stuffing bits are added which do not contain any information.
Some spaces are left in between data bits so that different sizes data blocks(Tributaries) can be added at same time.
Aligning is done in order to locate the first byte of the Virtual Container.
This process takes place before pointer addition to Tributary Units(TU) or Administrative Unit(AU).
Pointer is part of SDH frame which locates the start of floating Payload in the Frame
This process is used to adapt multiple Lower Order Path layer signals into a higher Order path signals or when higher order path signals are adapted into Multiplex Sections
C12 signal is mapped into Virtual Container VC12 further these VC’s are aligned for Pointer Processing.
Tributary Units are formed after pointer processing and such 3 units are multiplex together which gives higher order signal TUG2(Tributary Unit Group 2).
Again 7 TUG2’s are multiplex or combined together to form TUG 3 which is further higher Signal.
3 TUG3’s are multiplexed in VC4 container and it is aligned for pointer processing.
AU4( Auxilary Unit 4) is formed after pointer processing and then Higher Order Path Overhead (HO POH) is added to AU4 to give AUG1
All remaining stuff such as Pointer, RSOH(Regenerator Section Overhead) & MSOH(Multiplexer Section Overhead) is added to the AUG1 and STM 1 Frame is formed.
