Download GTU BE/B.Tech 2019 Summer 6th Sem Old 161001 Digital Communication Question Paper

Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 6th Sem Old 161001 Digital Communication Previous Question Paper

1
6Seat No.: ________ Enrolment
No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI(OLD) ? EXAMINATION ? SUMMER 2019
Subject Code:161001 Date:18/05/2019
Subject Name: Digital Communication
Time:10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) State and prove sampling theorem. 07
(b) Define Cumulative Distribution Function. State and prove the properties of CDF. 07

Q.2 (a) Draw and explain the block diagram of Pulse code Modulation (PCM). 07
(b) Define the Probability Density Function. Determine the mean, the mean square
value and the variance of the RV X whose PDF is given by px(x) = 0.5|?? |?? ?|?? |
.
07
OR
(b) A zero-memory source emits six messages with probabiltites 0.3, 0.25, 0.15,
0.12, 0.1 and 0.08. Find the entropy of the source. Obtain the compact binary
code and find the average code word length, the efficiency, and the redundancy.
07

Q.3 (a) State and prove Central Limit Theorem. 07
(b) Which the ideal properties of line codes. Derive the general expression for PSD
of a large class of line codes.
07
OR
Q.3 (a) Write a short note on: Regenerative Repeater. 07
(b) Why pulse shaping is required? What is Inter Symbol Interference? Explain
Nyquist first criterion for zero ISI.
07

Q.4 (a) Derive the equation for channel capacity of discrete memoryless channel. 07
(b) For a (6,3) code, the generator matrix G is
G=[
1 0 0 1 1 1
0 1 0 1 1 0
0 0 1 1 0 1
]
(a) Construct the code generated by this matrix.
(b) Prepare a suitable decoding table.
(c) Decode the received codeword 101100.
07
OR
Q.4 (a) Derive the equation for channel capacity of a band-limited AWGN channel. 07
(b) Explain the principle and generation of convolution code by example. 07

Q.5 (a) Explain the operation of QPSK transmitter and receiver. 07
(b) Explain coherent detection of Frequency-Shift keying (FSK) signal with
necessary equations.
07
OR

Q.5 (a) Explain the Qadrature Amplitude Modulation and demodulation in detail. 07
(b) Which are the different types of spread spectrum systems? Draw and explain the
block diagram of Direct Sequence Spread Spectrum (DSSS) system.
07

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