## Anna University Chennai EC2301 Digital Communication April May 2011 Past Exam Papers Free Download

Anna University ChennaiQuestion Paper Code:

B.E./B.Tech Degree Examination, April May 2011

Fifth Semester

Electronics and Communication Engineering

EC2301 Digital Communication

(Regulation 2008)

Time: Three Hours

Maximum: 100 Marks

Question Paper Type: Past Exam Papers

Note: New Subject Code in R-2013 is EC6501

PART A (10 x 2 = 20 Marks)

1. Give an example each for time limited and time unlimited signals.

2. Give an advantage and a disadvantage of digital communication.

3. State sampling theorem.

4. What is quantization error?

5. Define hamming distance.

6. What is mean by transparency with respect to line codes?

7. What is a matched filter?

8. Give two applications for eye pattern.

9. Draw the PSK waveform for 011011.

10. What is a non-coherent detection system?

PART B (5 x 16 = 80 Marks)

11 (a) Explain how PWM and PPM signals are generated.

OR

11 (b) (i)Classify channels.Explain the mathematical model of any two communication channels. (6)(ii) Explain Binary symmetric channel and Gaussian channel with their mathematical models. (Marks 10)

12 (a) (i)Explain a non-uniform quantization process.

(ii) Write notes on temporal waveform coding.

OR

12 (b) (i) Explain a spectral waveform encoding process.(ii) Compare various speeches encoding methods.

(13) (a)( i)Assume a (2,1) convolutional coder with constraint length 6.Draw the tree diagram,state diagram and trellis diagram for the assumed coder.

(ii) Find the (7,4) linear systematic block code word corresponding to 1101.Assume a suitable generator matrix.

OR

13 (b) Draw the power spectra of polar codes and on-off codes.Discuss their characteristics.14 (a) Derive the expression for bit error probability due to a matched filter.

OR

(b) Discuss on signal design for ISI elimination.15 (a) Derive the bit error probability due to coherent ASK, PSK and FSK systems.Compare the performance of these systems.

OR

15 (b) (i) Discuss QPSK signalling(b) (ii) Derive the bit error probability due to QPSK receiver. Compare the performance of QPSK receiver with that of PSK receiver.

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