Anna University Chennai 2011-6th Sem B.E Electronics & Communication Engineering Electronics & Communication Engineering EC-1351 Digital communication ,- Question Paper

B.E/B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011
SIXTH SEMESTER
ELECTRONICS AND COMMUNICATION ENGINEERING
EC1351- DIGITAL COMMUNICATION
(Regulation 2004)

PART-A
(10*2=20)

1. Difference ranging from the slope over load and granular noise in delta modulation systems.

2. describe instantaneous sampling.

3. Draw the frequency and time response of raised cosine spectrum.

4. What is the purpose of using eye pattern?

5. Compare M-ary and binary signaling schemes.

6. obtain the bit fault probability of a coherent PSK system.

7. Prove any 2 properties of Block Codes.

8. elaborate turbo codes?

9. Generate the PN sequence for [5,4,3,1].

10. Mention the merits and demerits of spread spectrum techniques.


PART-B
(5*16=80)

11.(a) Drive the expression for the sampling process in time domain. (16)
Or
(b) (i) discuss the principles of PCM with block diagram. (8)
(ii) Write brief notes on TDM. (8)

12.(a)(i)Derive the expression for the matched filter. (8)
(ii) explain the concept of correlative level coding. (8)
Or
(b) Write a brief note on Nyquist's criterion for distortion less base band binary transmission. (16)

13.(a) With a neat sketch, discuss the working of the coherent QPSK modulation and derive its bit probability. (16)
Or
(b) What is the need of carrier synchronization? discuss the various modes and methods of carrier used in digital modulation system. (16)

14.(a) The generator matrix for a Linear Block Coder is G= [row1= 0 0 one 1 one 0 1][row2= 0 one 0 0 one 1 1][row3=1 0 0 one 1 one 0]. Express G in systematic that the code word corresponding to the info sequences 101 is orthogonal to H. (16)
Or
(b) A message 101101 is to be transmitted in cyclic code with generator polynomial g(x)=x^4+x^3+1. find the transmitted code word. How many check bits does the encoded message contain? Draw the arrangement for the identical. (16)

15.(a) List and prove the properties of the PN sequence.
Or
(b) discuss the concept of DS/BPSK system and compare its performance with FH system. (16)

Earning:   Approval pending.