1. Conversion/Mapping of PDH Rates to SDH
Presented By:
Dr Muhammad Khalil Shahid
PTCL Training & Development

2. Mapping
Process of adapting tributaries into Virtual Containers (VCs) by adding justification bits and Path Overhead (POH) information
To make the various tributary signals synchronized with related virtual containers
VC can be an independent entity in the transmission, multiplexing and cross connection

3. Low Rate SDH → High Rate SDH: Byte Interleave
Continue..
Low Rate SDH → High Rate SDH: Byte Interleave
PDH → STM-N: Synchronous Multiplexing & Flexible Mapping
140M→STM-N
34M→STM-N
2M→STM-N
No container for E2 (8 Mbps)

4. Alignment
Process of including in a Tributary Unit (TU) or an Administrative Unit (AU) Pointers
To allow the first byte of the Virtual Container to be located
Provide a flexible and dynamic method for alignment of VC in the unit (TU or AU-4) frame

5. Multiplexing
Process of adapting multiple lower-order path layer signals into a higher-order path signal
When the higher-order path signals are adapted into a Multiplex Section
This type of multiplexing comes under synchronous multiplexing category

6. Stuffing
After multiplexing & aligning, some spare capacity is required to provide space for various tributary rates
This space capacity is filled with "fixed stuffing" bits that carry no information
Required to fill up the particular frame

7. Virtual Container (VC)
The digital flow from the standard container combined with path overhead forms a virtual container (VC)
C-4 + POH (9 bytes) = VC-4 (9x261 bytes)
C-3 + POH (9 bytes) = VC-3 (9x85 bytes)
C-12 + POH (1 byte) = VC-12 (35 bytes)
It is the most important information structure in SDH which supports path layer connection