Advantages of PDH | disadvantages of PDH
This page covers advantages and disadvantages of PDH. It mentions PDH advantages or benefits and PDH disadvantages or drawbacks. It also describes PDH basics.
What is PDH?
Introduction:
• PDH is the short form of Plesiochronous Digital Hierarchy.
• It is associated with digital exchanges.
• The different hierarchies having different rates are combined using PDH.
There may be 24 or 30 or multiple of these channels in tributaries.
• Inputs having same rates but are from different clock sources are combined in PDH.
• There are 30 channels in Europe, 24 channels in North America.
Japan uses different levels of PDH.
• Bit interleaving is used to combine signals.

Refer PDH versus SDH >>.
Benefits or advantages of PDH
Following are the benefits or advantages of PDH:
➨It was designed to support transportation of huge amounts of data over
digital equipments using various transmission mediums such as microwave radio or fiber optic systems.
➨Network management has been enhanced to greater extent.
➨It performs well in North America, Europe and Japan independently as per standard specifications.
Drawbacks or disadvantages of PDH
Following are the disadvantages of PDH:
➨ In PDH, different frame is used for transmission and in data layer.
Hence multiplexing and de-multiplexing is very complex.
➨ Accessing lower tributary requires the whole system to be de-multiplexed.
➨ The maximum capacity for PDH is 566 Mbps, which is limited in bandwidth.
➨ Tolerance is allowed in bit rates.
➨ PDH allows only Point-to-Point configuration.
➨ PDH does not support Hub.
➨ Every manufacturer has its own standards; PDH also has different
multiplexing hierarchies making it difficult to integrate interconnecting networks together.
PDH SDH RELATED LINKS
•SONET versus SDH •What is PDMA? •What is WDM? •SONET SDH tutorial •SDH Networks •SDH Frame structure •SDH Modulation •PDH over SONET •PDH Frame structure
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