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4.1 Explain the following with reference to PCM.


Sampling: Sampling a band limited analog signal at a frequency higher than twice the
maximum frequency of the analog signal

Quantizing: Non-linear quantizing of sampled values
Sampling Quantizing Encoding

Encoding: Assigning ‘0’s and ‘1’s for the quantized voltage levels

Sign: + or – (1-bit)
Segment No.: 3-bits
Level No.: 4-bits

4.2 What are the applications of TS0 and TS16 in the PCM frame.

TS0 - for Synchronization

TS16 - for sending Supervisory signals of Ch.1 to Ch.15 and Ch.17 to Ch.31

4.3 Briefly explain why higher order multiplexing is necessary in telecommunication.
In SMW4 submarine cable system, STM-64 is used which is equivalent to 10Gbit/s. Briefly
Explain how a bit in a sample is multiplexed and de-multiplexed if used SMW4.

Telecommunication involves transporting user information from one place to another.
When the number of simultaneous calls increase, capacity of the transporting media too
has to be expanded to carry the additional information content This increases the cost
hence the tariff..
As capacity/bandwidth is a crucial factor in telecommunication link design, it is necessary
to combine many user information in a transmitting station in such a way that individual
information contents are separated and retrieved at the receiving station.
Higher order multiplexing is used for this in telecommunication.
Different PCM streams are first multiplexed using either PDH or SDH technology and
transported through a same medium. At the receiving station, these PCM streams are demultiplexed.
This makes it possible to share the same transporting medium (microwave, copper cable
or optical fibers) by different PCM streams.