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6 Explain the basic difference between SDH and PDH transmission.

SDH support high data rates compared to PDH. Hence higher capacity equipment,
transmission media etc., are necessary. Because of these higher bandwidth requirements, it is
not possible to use certain transmission media and also have to limit the data rates in certain
mediums. (e.g. Microwave radio)

6.1 Clearly explain the difference between PDH and SDH multiplexing methods.

PDH and SDH are two different multiplexing techniques used in telecommunication. Their
main features are shown below in brief;

Less synchronized
Easy to operate
Absent of high network management features
Low data rates
High efficiency in allocating bits in the frame
More on manual control

Fully synchronized
More software oriented
Network management features available
High data rates
Low efficiency in the allocation of bits in the frame
Low user interaction necessary
Interoperability is possible

ii Assume three transmitting stations A,B and C.

Consider the following E1 distribution between above 3 stations.

Station 1 Station 2 No. of 2Mbit/s terminated
A B 33
B C 44
A C 16

(a) State the total utilization (Used 2Mbit/s/Total 2Mbit/s available) of each link. (AB and BC)

Link AB:
Used E1/Total E1 = 49/64 = 0.77

Link BC:
Used E1/Total E1 = 60/64 = 0.94

(b) State the capacities of transmission equipment to be used, so that the link utilization is
optimum, in these 3 stations if use,

PDH technology

Link AB:
Same, i.e. 140Mbit/s

Link BC:
Same, i.e. 140Mbit/s

SDH technology

Link AB:
STM-I (155.52Mbit/s)

Link BC:

iii. Explain clearly the advantages and disadvantages of SDH.

Provision of high data rates
Availability of advanced network management facilities
Less user interaction
Interoperability is possible

High cost
Complex systems
High skill of staff required