Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2018 Winter 6th Sem Old 161001 Digital Communication Previous Question Paper
1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI (OLD) EXAMINATION ? WINTER 2018
Subject Code:161001 Date: 30/11/2018
Subject Name: Digital Communication
Time: 02:30 PM TO 05:00 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 the Sampling theorem with necessary equation & waveforms. 07
(b) In a random experiment, a trial consists of four successive tosses of a coin. If we
define an RV x as the number of heads appearing in a trial, determine
probabilities PX(x) and CDF FX(x).
07
Q.2 (a) Define Delta modulation? Draw the neat diagram of Delta modulator & explain
the operation with waveforms.
07
(b) What is Cumulative Distribution Function (CDF)? Enlist the important properties
of CDF ? Prove any two of them.
07
OR
(b) Define : Code efficiency, Entropy, Redundancy, Binary Symmetric Channel.
Mean, Standard Deviation & Moments of random variable.
07
Q.3 (a) A memory-less source emits messages m1 to m6 with probabilities 0.3, 0.25, 0.15,
0.12, 0.10, 0.08 respectively. Find the length of this code (L), entropy of source
(H), code efficiency & redundancy for binary Huffman code.
07
(b) What is line coding? Explain the desirable properties of line codes. 07
OR
Q.3 (a) Find the channel capacity of Binary Symmetrical Channel. 07
(b) What is the need for pulse shaping? Explain Nyquist?s Criterion for zero ISI. 07
Q.4 (a) Explain in details the Amplitude Shift Keying (ASK). 07
(b) For a (6, 3) systematic linear block code, the three parity check digits c4, c5, c6
are c4 = d1 + d2 + d3
c5 = d1 + d2
c6 = d1 + d3
(i) Construct the appropriate generator matrix for this code. (ii) Construct the
code generated by this matrix. (iii) Determine the error correcting capabilities of
this code. (iv) Prepare a suitable decoding table.
07
OR
Q.4 (a) Describe coherent & non-coherent detection of FSK signal. 07
(b) State & Prove Central Limit Theorem. 07
Q.5 (a) What is Spread Spectrum system? Describe Direct Sequence Spread Spectrum
System in detail.
07
(b) Explain briefly BPSK modulation with neat sketch. 07
OR
Q.5 (a) Explain QPSK technique including QPSK transmitter & receiver. 07
(b) Difference between Analog & Digital Communication System. Also explain
block diagram of Digital Communication.
07
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This post was last modified on 20 February 2020