8/9/2019 ST III DC QP 2010

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GNANAMANI COLLEGE OF TECHNOLOGY

Department of ECE

SERIES TEST-III

Subject: Digital Communication Date : 23.03.2010Branch/Semester: ECE/VI Time : 3 Hrs

Max. Marks : 100

Answer ALL questions

PART A (20X 2=40)

1. What is meant by aliasing effect?2. Differentiate coherent and non coherent receiver.3. What is the use for Eye pattern?4. What is meant by constraint length of a convolution code?5. What is meant by granular noise?6. What is meant by Hamming distance?7. Define BCH code.8. Give the special features of Trellis code.9. What is meant by correlative level coding?10.Compare code tree and trellis diagram.11.Draw the block diagram of the transmitter and receiver sections of DPCM.12.What is the error probability of MSK and DPSK?13.What is a convolution code?14.What is inter symbol interference? Explain.15.Obtain the parity check matrix of a (5, 1) repetition code whose generator

matrix is G =[11111].

16.Compare the bandwidth efficiency of the M-ary FSK and M-ary PSKmodulation schemes.

17.Define quantization error.18.Why do we need equalization in base band pulse transmission?19.What are the advantages and disadvantages of differential phase shift keying?20.Define pulse position modulation with suitable diagram.

P.T.O

Q-II

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PART B

Answer any FIVE questions (5X12=60)

21. With the help of a neat block diagram, explain the encoder and decoder ofdifferential PCM system. Also obtain an expression for prediction coefficientfirst order predictor.

22. Derive and plot the power spectra of NRZ uni polar and bipolar formatsignals.

23.Draw the block diagram of duo binary encoder and decoder and explain. Whatare the draw backs of this scheme? Suggest a method to overcome the same.

24. With necessary equations and signal space diagram, obtain the probabilityof error for coherent binary FSK system.

25.(i)For a uniform quantizer, discuss the way in which the number ofquantization levels(L) influence the bandwidth and the quantization noise. (3)(ii)Discuss the need for Non-uniform quantization of speech signal. (3)

(iii)Outline the principles of compander used for speech signal. (4)(iv)Give the bit rate of a delta modulator fed with samples at a rate of 40

samples/sec. (2)

26. The generator matrix for a (6, 3) block code is given below. Find all codevectors for this code.

100: 011

G= 010: 101001: 110

27.Derive the expression for matched filter and prove anyone property.28.Consider a rate ,non systematic convolutional code with, g(1)={1,0,1} and

g(2)={1,1,1}.Determine the encoder output corresponding to the data sequence

{1,0,1,0,1}.If the first and fourth bits of the encoded sequence are affected

during transmission, demonstrate the error correcting capability of the viterbi

algorithm.

STAFF I/C HOD/ECE

8/9/2019 ST III DC QP 2010

3/4

GNANAMANI COLLEGE OF TECHNOLOGY

Department of ECE

SERIES TEST-III

Subject : Digital Communication Date : 23.03.2010

Branch/Semester: ECE/VI Time : 3 HrsMax. Marks : 100

Answer ALL questions

PART A (20X 2=40)

1. List out uses of sampling theorem.2. What is anti aliasing effect?3. What is and A law?4. . Define mid tread quantizer.5. Draw the block diagram of base band binary data transmission.6. A band pass signal has the spectral has the spectral range that extends from 20 kHz to

82 kHz. Find the acceptable range of sampling frequency fs?

7. What is sensitivity of an eye?8. What is the main disadvantage of duo binary scheme?9. Define non coherent FSK.10.What is maximum likelihood detector?11.Give the signal space characterization of QPSK.12.What are the three types of synchronization?13.Write the expression for bit error rate for coherent binary FSK.14.What is meant by RS coding?15.Define channel coding.16.

State Nyquist criterion for zero ISI.

17.What is meant by correlative coding?18.Define linear block code.19.What is meant by constraint length of a convolution code?20.What is the SNR of PCM system if number of quantization levels is 28?

P.T.O

Q-I

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PART B

Answer any FIVE questions (5X12=60)

21.Describe the following systems by presenting appropriate diagrams.(i)TDM (ii) Delta modulation.

22.Draw the block diagram of the duo binary signaling scheme and derive the overallfrequency response of this scheme.

23. Explain BPSK signal transmission and coherent BPSK reception with suitable

diagrams. Derive an expression for the probability of symbol error for the scheme.

24. (i)State and prove the properties of syndrome decoding.

(ii)Describe a decoding procedure for linear block code.

25. (i)Design the encoder for the (7,4) cyclic code generated by G(p)=p3+p+1 and verifyits operation for any message vector. Find all the code vectors for the code in

nonsystematic form. (ii)Give the properties of cyclic codes.

26. Draw the block diagram of MSK transmitter and receiver and discuss in detail with

required waveform.

27. Find all cyclic codes (7, 3) for the generator polynomial g(x)= x4+x+1.

28. Enumerate on carrier and symbol synchronization.

STAFF I/C HOD/ECE