B.Tech V (Fifth) Semester Examination 2014-15
Course Code: EEC504 Paper ID: 0965218
Digital Communication System
Time: 3 Hours Max. Marks: 70 Max Marks: 75
Note: Attempt six questions in all. Q. No. 1 is compulsory.
Assume suitable data, if missing.
1. Answer any five of the following (limit your answer in 50 words). (4x5=20)
a) Define channel capacity.
b) What is Shanon-Fano coding?
c) Write down the advantages of digital communication systems.
d) Write the five points of comparison between PCM and DM systems.
e) Write the five similarities between BFSK and BPSK.
f) Define the information and its properties.
g) Define Information rate for a channel.
h) What it is the difference between Error detection and error correction capabilities?
2. Explain the working of PCM Communication system with neat diagram. Give the suitable reason of choosing PCM over analog modulation techniques. (10)
3. Given a sine wave of frequency fm and amplitude Am applied to a delta modulator having step size. Show that the slope overload distortion will occur if (10)
4. What is the purpose of Hamming code? A receiver receives the code 11001100111. When it uses the Hamming encoding algorithm, the result is 0101. Which bit is in error? What is the correct code? (10)
5. Calculate the BER of FSK signaling when coherent receivers are used for the detection process. (10)
6. What is non coherent modulation? How it can be done , when transmitter send the information in phase. Write the suitable steps involve in transmission and detection. (10)
7. Write short notes on any two of the following: (5+5)
a) Linear Block codes
b) BCH Codes
c) DPCM
8. a) Define average mutual information between two discrete random variables and show that it is non negative. (5)
b) An event has six possible outcomes with probabilities
P1=1/2 ;p2=1/4 ; p3=1/8 ; p4= 1/16 , p5= 1/32 and p6=1/32
Find the entropy of the system. Also find the rate of information if there are 16 outcomes per second. (5)