Friday, 15 March 2013

Line Rates and Hierarchy in SDH & SONET

The first hierarchy level for SDH is set at 155,520 kbit/s/s.
This is known as a Synchronous Transport Module 1 (STM-1).
Higher levels are simply multiples of the first level.

SDH allows for various PDH input rates to be mapped into containers as shown below:
  • Container C11:      1544 kbit/s                  (1.5 Mbit/s) 
    Container C12:      2048 kbit/s                  (2 Mbit/s)
    Container C2:        6312 kbit/s                  (6 Mbit/s)
    Container C3:        49,536 kbit/s               (45 & 34 Mbit/s)
    Container C4:        139,264 kbit/s             (140 Mbit/s) 

    As can be seen from this chart, the only PDH rate that is not supported by SDH is 8 Mbit/s


  1. Why is the PDH rate 8 Mbit/s not included in SDH ?

  2. 8 Mbps was not used frequently. So, it was not adopted into SDH multiplexing