SKR ENGINEERING COLLEGE, Chennai – 600123

INTERNAL ASSESSMENT TEST – 1

Branch : ECE A&B Semester : VSubject Code : EC 2301 Date : 22.07.2013Subject Name : DIGITAL COMMUNICATION Timings : 3hoursTotal Marks : 100

PART – A: Answer ALL Questions: (10 X 2 = 20 Marks)

1. Define spectral efficiency?2. Define null to null bandwidth.3. Compare uniform and non uniform quantization Nov/Dec 2011 4. what is meant by temporal waveform coding Nov/Dec 2011 5. state sampling theorem for low pass signals MAY/JUNE 20126. How can BER of a system be improved? Nov/Dec 2012 7. What are the different types of encoding techniques?8. What are the advantages of digital representation of analog signals?9. Why prefiltering is necessary in sampling process10.Define dimensionality theorem

PART – B: Answer ALL Questions: (5*16=80 Marks)

11. a) Explain in detail the Gram-Schmidt orthogonalisation procedure. Nov/Dec 2012 (8) b) Explain the geometric representation of signals May/June 2012 (8) 12.a )Draw the block diagram of digital communication systems and each block in detail

May/June 2012 (10) b) State the advantages and disadvantages of a digital communication system Nov/Dec 2012 (6)

13. a)Discuss in detail the different mathematical models of communication channel Nov/ Dec 2011 (8) b)Explain a nonuniform quantization process April/May 2011 (8)

14. Explain the different types of pulse modulation techniques (16) 15. Explain the working of pulse code modulation and demodulation system May/June 2012 (16)

SKR ENGINEERING COLLEGE, Chennai – 600123

INTERNAL ASSESSMENT TEST – 1

Branch : ECE A&B Semester : VSubject Code : EC 2301 Date : 22.07.2013Subject Name : DIGITAL COMMUNICATION Timings : 3hoursTotal Marks : 100

PART – A: Answer ALL Questions: (10 X 2 = 20 Marks)

1. What are the advantages and disadvantages of digital communication? April/May 20112. How PDM wave converted into PPM system?3. What is the bandwidth of PCM?4. What is meant by quantization? May/June 20125. What is meant by aliasing? How to eliminate aliasing.6. Define Half power bandwidth. Nov/Dec 2011 7. What is quantization error? April/May 20118. What is meant by figure of merit of a digital communication system? Nov/Dec 2010 9. Differentiate the principles of temporal waveform coding and model based coding. Nov/Dec 2012 10. What are the properties of basis function?

PART – B: Answer ALL Questions: (5*16=80 Marks)

11. Explain the following sampling techniques with necessary waveforms i) natural sampling May/June 2012 (8) ii) impulse sampling May/June 2012 (8)

12.With neat block diagram explain pulse code modulation and demodulation system May/June 2012 (16)

13. (a)Explain any three communication channel models. April/May 2012 (8) (b)Explain how PWM and PPM signals are generated?. April/May 2011 (8)

14. (a )With neat diagram explain the functional description of digital communication systems. May/June 2012 (10)

(b) Distinguish between base band and bandpass signaling. (6)

15. (a)explain the uniform quantization process (6) (b)Consider the signals s1 (t), s2 (t), s3 (t), shown in figure. Using Gram-Schmidt orthogonalisation procedures derive the basis functions corresponding to the given signals. (10)