Q Bank.docx

BITS EDU CAMPUS ELECTRONICS AND COMMUNICATION DEPARTMENT SUBJECT NAME: DIGITAL COMMUNICATION SUBJECT CODE: 2161001 Syllabus for mid sem 2019

QUESTION BANK Unit-1 Probability Theory 1. State and Prove central limit theorem 2. Define Probability. Explain conditional and joint probabilities 3. Define the terms Mean, Central moment and Variance of a Random Variable. 4. Explain Baye’s Rule. 5. Explain Gaussian Random Variable. Unit 2: Information Theory State and explain Shannon’s theorem on Channel capacity Define Entropy of source. Huffman coding examples- binary, ternary, tertiary, second order and third order extension. Show that for n messages the maximum value of entropy is log n. Entropy of band-limited white Gaussian noise. Prove that for a white gaussian channel noise, the channel capacity C approaches a limit of 1.44 S/η as B→∞ 12. Channel capacity of bandlimited AWGN channel. 6. 7. 8. 9. 10. 11.

Unit 3: Baseband modulation Explain companding process in PCM and state the different laws for companding. Explain Pulse Code Modulation in detail. Derive the expression for signal to quantization noise of PCM Explain the operation of Delta modulation and adaptive delta modulation using neat diagram and waveforms.. Also discuss its advantages and disadvantages 17. Explain sampling theorem. State and prove that a signal whose spectrum is band-limited to B Hz can be reconstructed exactly from its samples taken uniformly at a rate R > 2B Hz. Also explain the practical difficulties in signal reconstruction. 18. Explain various types of sampling techniques and compare them. 19. A binary channel matrix is given by y1 y2 2/3 1/3 x1 ( ) 1/10 9/10 x2 Px(x1)=1/3 and Px(x2)=2/3. Determine H(X), H(Y), H(X/Y), H(Y/X) and I(X;Y) Unit 4: Error correcting codes 20. What is hamming bound and derive the expression for hamming bound. Linear block code example. 21. Explain Convolutional codes along with code tree, state transition diagram and trellis diagram 22. Construct a systematic (7,4) cyclic code using a generator polynomial g(x)=x3+x2+1 13. 14. 15. 16.

Unit 5: Principles of digital data transmission 23: Line codes and their PSDs 23. What is ISI, factors responsible for ISI, remedy to reduce ISI 24. Scrambling and unscrambling 25. Explain Eye diagram and timing jitter