B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010
Fifth Semester
Electrical and Electronics Engineering
EC 2311 — COMMUNICATION ENGINEERING
(Regulation 2008)
Time : Three hours Maximum : 100 Marks
Answer ALL questions
PART A — (10 × 2 = 20 Marks)
1. Mention the disadvantages of single sideband transmission.
2. The carrier frequency of an FM broadcast transmission is 100 MHZ and maximum frequency deviation is 75 KHZ. Find the Bandwidth of the signal when the highest audio frequency modulating the carrier is 15 KHZ.
3. What are the elements of digital communication system?
4. How does the phase of carrier vary for the message m(n) ={ 1,0,1,1,0,1 ,...}?
5. An event has six possible outcomes with probabilities {1/2, 1/4, 1/8, 1/16, 1/32, 1/32}. Find the entropy of the system.
6. Find the Hamming distance between the following code words
C1 ={1000111} and C2 ={0001011}.
7. Mention the advantages of CDMA system.
8. Specify uplink and downlink frequency ranges for satellite communication.
9. State the advantages of fiber optic system.
10. What is geosynchronous satellite?
PART B — (5 × 16 = 80 Marks)
11. (a) (i) Explain the principle of indirect method of frequency modulation with neat sketch. (8)
(ii) A carrier wave of 10 MHZ is amplitude modulated to 50% level with a tone of 5000 HZ. Sketch the waveform and amplitude distribution in time and frequency domain. Assume carrier amplitude as 10 V. (8)
Or
(b) (i) Draw the block diagram for generation and demodulation of a VSB signal and explain the principle of operation. (10)
(ii) With suitable sketch discuss about square law detector. (6)
\
12. (a) With a neat block diagram explain the PAM modulation and demodulation process and derive an expression for PAM wave and depth of modulation. (16)
Or
(b) (i) Explain working principle of ASK modulator and detector with neat diagram. (10)
(ii) Draw ASK, FSK, PSK signal to transmit the data stream
1111000111. (6)
13. (a) (i) Brief the properties of entropy. (4)
(ii) Five symbols of the alphabet of discrete memory less source and their probabilities are given below.
S ={S0,S1,S2,S3,S4}
P (S) ={ 1.0,1,0,2.0,2.0,4.0 }
Code the symbols using Huffman coding. (12)
Or
(b) (i) Briefly discuss on various error control codes and explain in detail with one example for convolution code. (12)
(ii) Draw the polar, unipolar, bipolar and Manchester NRZ line code format for an information {1 0 11 0 0}. (4)
14. (a) (i) Discuss the BSC and BEC with their channel diagram and transition matrix. (12)
(ii) Consider that a source is transmitting equiprobable 1/0 at the rate of 103 b/s and the probability of error is Pe =1 16. Determine the rate of transmission. (4)
Or
(b) Discuss the various multiple access techniques used in wireless communication with their merits and demerits. (16)
15. (a) (i) Compare optical fiber cable with RF cable. (6)
(ii) Distinguish among single mode step index, multimode step index and multimode graded index optical fibers. (10)
Or
(b) Give short notes on the following :
(i) Satellite subsystems (8)
(ii) Power line carrier systems. (8)