EC2301 Digital Communication Nov / Dec 2013 Important Questions - Anna University 5th Semester ECE Part B Important Question for Nov Dec 2013 Exam
UNIT I
1. Draw a neat block diagram of a typical digital communication system and explain the function of the key signal processing blocks.(16)
2. (i) distinguish between baseband and bandpass signaling.(6)
(ii) Brief discussion about types of analog pulse communication system.(10)
3. Explain how PWM and PPM signals are generated.(16)
4. Explain the mathematical model of any two communication channels.(16)
5. (i) Explain the geometrical representation of signals. (8)
(ii) Explain GSOP procedure. (8)
UNIT 2
1. State the nyquest sampling theorem. Demonstrate its validity for an analog signal x (t)
having a fourier transform x (f) which is zero outside the interval [- fm <f < +fm] (16)
2. Explain in detail the various source coding technique for speech signal and comparetheir performance. (16)
3. (i) Explain a spectral waveform encoding process. (8)
(ii) Compare various speeches encoding method. (8)
4. Explain PCM and its types. (study other Systems also) (16)
5. Explain delta modulation and its types and explain how to remove noise in DM (16)
UNIT 3
1. Derive the power spectra of polar codes and on-off codes. Discuss their characteristics. (16)
2. (i) Explain how encoding is done by convolutional codes with suitable diagram of convolutional codes. (6)
3. (i) Explain the power spectra of unipolar NRZ and RZ. (10)
(ii) Find the generator matrix of (7, 4) cyclic code. (6)
4. (i) list and explain the properties of line codes. (4)
(ii) Explain the transform domain approach analysis of convolutional code. (6)
UNIT-4
1. What does the term equalization refer to? Explain how it is carried out by using transversal filters. (16)
2. Derive the expression for bit error probability due to a matched filter.
(16) example. (10)
(ii) Explain tree diagram, trellis diagram and state transition
(iii) Derive the power spectral density of polar signaling and explain. (6)
3. (i) Define a matched filter and compare its functioning with a correlator. (10)
(ii) Explain how matched filter can maximize SNR for a given transmitted symbol. (6)
4. Discuss on signal design for ISI elimination and State Nyquest pulse shape criterion for zero ISI and explain. (16)
5. Derive the expression for error probability of on-off and polar signaling. (16)
Explain the scheme with and without precoder. (10)
UNIT-5
1. Derive the bit error probability due to coherent ASK, PSK and FSK systems. Compare the performance of these systems. (16)
2. (i) Distinguish coherent and non-coherent detection. (4)
(ii) Explain non-coherent detection methods of binary frequency shift keying scheme. (12)
3. (i) derive the power spectral density of binary ASK signal. (6)
(ii) Obtain the probability of bit error for coherently detected BPSK and compare itsprobability of bit error performance with QPSK scheme.(8)
4. (i) discuss QPSK signaling. (4)
(ii) Derive the bit error probability due to QPSK receiver. Compare the performance of QPSK receiver with that of PSK receiver. (12)
5. (i) Draw the block diagram of duo-binary signaling scheme for controlled ISI.
6. Explain the concept of coherent BPSK & QPSK with transmitter and receiver block diagrams and obtain the expression for probability of error.(16)
7. (i) Draw the functional block diagram of modulator for QAM and explain its operation. (8)
(ii) Derive the expression for error-probability of QAM system.(8)
Hints : Study repeated questions of previous year anna university question papers
For problems : refer Unit 3.
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