Master of Science II (Electronic- Communication Science)
Examination: Oct Nov 2016 Semester III (Old CGPA)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR SJ
350
Friday
18/11/2016
02:30 PM
to
05.00 PM
Digital Communication
C
X
Instructions: All questions carry equal marks.
Q.1 and Q.2 are compulsory.
Attempt any THREE questions from Q.3 to Q.7
Total Marks: 70
Q.1 Select the most correct alternative- 06
In PCM system, the number of quantization levels is 32 and the maximum
signal frequency is 4 kHz. The bit transmission rate is
8 kbps 16 kbps
32 kbps 40 kbps
A source generates 4 messages the Entropy of the source will be
maximum when
all probabilities are equal.
two of the probabilities equal 1 and two other are zeros
the probabilities are ½, ¼ and ½
the two of probabilities are ½ each and other two are zeros
The coding efficiency is given by
1/redundancy 1 redundancy
redundancy None of these
If fm is modulating frequency than aliasing occurs, when Nyquist rate is

2 fm 3 fm
2.5 fm 1.2 fm
The phase difference between two possible transmitted signals in QPSK is

Which of the following gives maximum probability of error
ASK BPSK
BFSK DPSK
State whether following statements are true or false: 08
Channel capacity of a noise free channel having M symbols is given by
2M.
Multiplexing techniques provide security in digital communication.
In an Eye diagram representation, more opening of the Eye indicates more
distortion.
BW of BPSK is higher than BFSK.
Page 1 of 2
The information rate is defined to be average number of bits of
information/second.
Compared to binary signaling scheme Mary signaling scheme are more
complex.
Tossing of a coin is the example of continuous random variable.
'Man bites dog' This statement carries maximum information.
Q.2 Write Short notes:
Adaptive Equalizer 05
Adaptive delta modulation 05
Stationarity and Ergodicity of random processes 04
Q.3 What is mutual information? Prove I H H 08
Prove Bay's theorem. 06
Q.4 With block diagram explain working of PCM system. How does it differs
with respect to DPCM.
08
Find all code words for cyclic code for generator polynomial g
1+x2.
06
Q.5 Apply the Huffman coding procedure for the following message ensemble.
Calculate its efficiency.
[x1 x2 x3 x4 x5 x6 x7 x8]
1/8 1/16 1/16 1/16 1/4 1/16
Assume M 2
08
Explain frame synchronization. 06
Q.6 Find all code vectrors for a linear block code for given generator matrix,
draw encoder. Also write its parity check matrix.
08
What is information and entropy? Explain the characteristics of entropy. 06
Q.7 Explain M-ary PSK modulation in detail. 08
Compare random variables. 06