GTU Digital Communication - May 2016 Exam Question Paper

GTU Electronics and Communication Engineering (Semester 6)
Digital Communication
May 2016

Total marks: --
Total time: --

INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) Define random variable and find the mean, the mean square and the variance of the general Gaussian random variable.

7 M

1 (b) Explain briefly Nyquist's sampling theorem. What is Interpolation process? Derive Interpolation formula.

7 M

2 (a) Derive channel capacity C if channel noise is additive, white Gaussian with mean square value N, given signal power S.

7 M

Solve any one question from Q2(b) & Q2(c)

2 (b) A binary channel matrix is given by

	y1	y2
x	2/3	1/3
x2	1/10	9/10

x1,x2=input y1,y2=output
Px(x1)=1/3 and Px(x2)=2/3. Determine H(X), H(Y), H(X/Y), H(Y/X) and I(X;Y).

7 M

2 (c) A zero-memory source emits messages m1 and m2 with probabilities 0.8 and0.2, respectively. Find the optimum (Huffman) binary code for this source as well as for its second - and third ' order extension (that is, for N = 2 and 3). Determine the code efficiencies in each code.

7 M

Solve any two question from Q3(a), Q3(b) & Q3(c), Q3(d)

3 (a) What is line coding? What are the ideal requirements from line coding? Draw waveform of bipolar AMI coding for the sequence 10100101.

7 M

3 (b) Explain Delta Modulation in detail. Also discuss its advantages and disadvantages.

7 M

3 (c) What is Inter Symbol Interference? Explain the Nyquist's first criteria for zero ISI.

7 M

3 (d) What are the functions of regenerative repeater? Fully Explain the zero forcing equalizer with expressions.

7 M

Solve any two question from Q4(a), Q4(b) & Q4(c), Q4(d)

4 (a) Derive the general expression of Bit Error Rate (BER) for Optimum Binary Receiver.

7 M

4 (b) For ASK modulated signal, derive the expression of bit error probability using non-coherent detection.

7 M

4 (c) What is the multi-amplitude signalling? Derive the BER for the same using matched-filter receiver.

7 M

4 (d) Explain mathematical and graphical representation of BPSK. Explain BPSK generation.

7 M

Solve any two question from Q5(a), Q5(b) & Q5(c), Q5(d)

5 (a) Explain the generation of linear block code using suitable example.

7 M

5 (b) 1. Construct the systematic (7,4) cyclic code using the generator polynomial g(x)=x³+x+1
2. What are the error correcting capabilities of this code?
3. Construct the decoding table.
4. If the received word is 1101100, determine the transmitted data word.

7 M

5 (c) Explain QPSK with waveforms, constellation diagram and mathematical representation.

7 M

5 (d) Write short note on Convolutional coding.

7 M

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