VTU Electronics and Communication Engineering (Semester 5)
Information Theory & Coding
June 2014
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) A pair of dice are tossed simultaneously in an experiment outcome first dice is recorded as x1 and 2nd dice as x2 If the two event are:
A{x1, x2 such that x1-x2?8}; B{x1, x2 such that x1 > x2 }
Then determine i) Self information of A and B; ii) Entropy of the experiment.
6 M
1 (b) Consider the state diagram of a Markov source. Determine: i) State probabilities; ii) Entropy of each state; iii) Entropy of sourse.

8 M
1 (c) Discuss: i) Additive property of entropy; ii) Symmetrical property of entropy.
6 M

2 (a) Find the minimum number of symbols 'r' in the coding alphabet for devising an instantaneous code such that W={0, 5, 5, 1, 5} device such a code. Where 'W' represent set of code word of length: 1,2,....n.
6 M
2 (b) Construct a binary code for a source with five symbols S={s1, s2, s3, s4, s5} with respective probabilities P={-3, -2, -2, -15, -15}. Determine code efficiency using Shannon's coding.
8 M
2 (c) For the given channel matrix, calculate, H(x), H(y) and channel capacity given P(x1)=6 P(x2)=3 and P(x1)=-1 \[ P(y/x) = \begin{bmatrix} 1/2 &1/2 &0 \\ 1/2 &0 &1/2 \\0 & 1/2 &1/2 \end{bmatrix} \]
6 M

3 (a) Design a quaternary and binary source code for the source shown using Huffman's coding procedure S={s1, s2, s3, s4, s5, s6, s7}; P={-18, -17, -16, -15, -10, -08, -05} also determine code efficiency.
10 M
3 (b) Determine channel capacity of a binary erasure channel.
10 M

4 (a) Consider a random variable 'x' wholes PDF is shown in Fig. Q4 (a).
i) Determine the entropy of the source producing this variable.
ii) If the signal is passed through a linear amplifier of gain '8' determine entropy of o/p.

8 M
4 (c) A CRT terminal is used to enter alphanumeric data in a system. CRT is connected through a telephone with B,W=3kHz and [S/N]0=10dB. Assuming the terminal has 100 characters and data is sent in an independent manner with equal probability:
i) Find average information per character.
ii) Capacity of channel
iii) Data rate.
8 M

5 (a) Define the terms; i) Burst error; ii) Systematic linear block code: iii) Ealois field; iv) Hamming weight.
4 M
5 (b) For a systematic (6, 3) linear block code, the parity matrix is \[ [p]= \begin{bmatrix}1 &0 &1 \\0 &1 &1 \\1 &1 &0 \end{bmatrix}. \] Find all possible code vectors and parity check matrix.
6 M
5 (c) Construct the standard array for example in Fig. Q5(c). Hence determine corrected vector if received vector, z='000011'.
10 M

6 (a) For a (7,4) cyclic code the received vector Z(x)=0100101 and the generator polynomial is g(x)=1+x+x3, Draw the ksyndrome calculation circuit and correct the single error in the received vector also explain operation of circuit.
10 M

Write short notes on:
7 (a) Burst-error correcting codes.
5 M
7 (b) BCH code.
5 M
7 (c) Golay code.
5 M
7 (d) Shortened cyclic codes.
5 M

8 For a (2,1,3) convolutional encoder with g(1)=[1101], g(2)=[1011].
a) Draw the convolutional encoder block diagram.
b) Write down the stat transition table.
c) Draw the code tree.
d) Find the encoder o/p produced by message sequence 1101" by traversing through the code tree."
20 M



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