Digital Communication - May 2012

Electronics & Telecomm. (Semester 6)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks. 1 (a) Explain Shanon Hartley Theorem.(5 marks) 1 (b) Discuss the significance of Eye Pattern.(5 marks) 1 (c) Explain Viterbi Algorithm.(5 marks) 1 (d) Compare ISI and ICI.(5 marks) 2 (a) State and prove Sampling Theorem for low pass signal.(10 marks) 2 (b) Derive an expression for entropy.
A Gaussian channel has 2MHz bandwidth. Calculate the channel capacity if the signal power to noise spectral density ratio is 10⁵ Hz. Also find the maximum information rate.(10 marks) 3 (a) Why line codes are required for digital communication? Draw the following line code formats for the given data format 01101001.
(i) Polar RZ.
(ii) RZ-AMI
(iii) Unipolar NRZ
(iv) Differential Manchester.(10 marks) 3 (b) Draw the block diagram of QASK transmitter and receiver and explain its functioning.(10 marks) 4 (a) Compare the following:
(i) BPSK and DPSK.
(ii) Systematic and Non systematic codes.(10 marks) 4 (b) Derive an expression for probability of error of a matched filter. (10 marks) 5 (a) Explain syndrome decoding for Cyclic Codes.(10 marks) 5 (b) Draw the encoder for a (7,4) cyclic Hamming code generated by the generator polynomial G(D) = 1 + D + D³.(10 marks) 6 (a) Draw the block diagram of M Ary FSK transmitter and receiver and explain the working.(10 marks) 6 (b)

An error control code has the following parity check matrix.

$= \begin{bmatrix} 1 &0 &1 &1 &0 &0 \\\\1 &1 &0 &0 &1 &0 \\\\0 &1 &1 &0 &0 &1 \end{bmatrix}$

(i) Determine the generator matrix G.
(ii) Find the code words that begin with 101.
(iii) Decode the receive code word 110110.

(10 marks)

Write short notes on:

7 (a) Equalization.(7 marks) 7 (b) Bit Synchroniser. (7 marks) 7 (c) CRC codes.(7 marks)