essentially involves transporting of information from one place
Explain why digital transmission cannot be achieved by merely following
Sampling theorem involves in three processes i.e. Sampling such
that fs < 2fm (fm is the
maximum frequency of the band limited signal), Media, by low-pass
filtering the original
signal can be obtained. Here reproducing the samples through a transmission
cannot be achieved. Hence a technique is used to resolve this. i.e.
Explain the basic process of Pulse Code modulation.
Sampling ---- Quantizing – Encoding
In practice, non-linear quantizing is deployed as against linear
quantizing, explain the
reasons behind. 256 levels are used for non-linear quantizing and
there are 8 segments
each positive and negative sample. Explain the basic characteristics
quantizing used for European system (the A-law signal compression
of 13 linear
NLQ is used to provide a good S/N ratio for
a wider span of signals. This is essential as
about 90% of the signals lie between +Vm/2 and –Vm/2.
The following shows the NLQ characteristics.
Each quantized level will be converted to binary before transporting
the quantized level
(related to the sample) into the transmission media. Assuming a
telephone will generate a
maximum of +3072 mV calculate the encoded format that will be sent
in the transmission
media for the following sample values.
i. + 2210mV
ii. + 128mV
iii. – 14mV
i. +2210mV = 1 111 0110
ii. +128mV = 1 011 0100
iii. –14mV = 0 000 1000
iv. –416mV = 0 101 0000