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Name of the College : Valliammai Engineering College
University : Anna University
Department : Electronics and Communication Engineering
Subject Code/Name : CU7102 Advanced Digital Communication Techniques
Degree : M.E Communication Systems
Year : I
Semester : I
Document Type : Question Bank
Website : valliammai.co.in

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Valliammai Digital Communication Question Paper

Unit I Coherent And Non-Coherent Communication :
Part A :
1. What is a Non-Coherent Receiver?

Related : Valliammai Engineering College CU7301 Advanced Satellite Based Systems M.E Question Bank : www.pdfquestion.in/2792.html

2. Define Rician Channel
3. Define Rayleigh Channel.
4. State the need for WGN.
5. Compare DPSK and PSK.
6. What are the merits and demerits of coherent receivers?
7. Define carrier synchronization
8. Enumerate the properties of Rician channel ?
9. What is the difference between coherent and non- coherent communication ?
10. What is partially coherent receiver?
11. Draw the power spectra for M-PSK and M-QAM modulation.
12. Draw the waveform communication model.
13. What is matched filter?
14. What is a M-PSK receiver?
15. What is the significance of optimum M-FSK receivers?
16. Draw the non-coherent receiver for equal energy signals using envelope detector.
17. Give the performance of Rayleigh channels
18. Give the performance of Rician channels
19. What is a M-ary waveform receiver?
20. Compare coherent and non coherent receivers.

Part B :
1. Discuss in detail the various aspects of the matched filter.
2. Compare the BER performance analysis of DPSK, M-PSK and M-DPSK.
3. With a suitable diagram explain the M-DPSK receiver.
4. With a neat block diagram explain the function of DPSK and MPSK demodulators.
5. Describe the function of M – FSK receiver.
6. What is a coherent receiver? Explain in detail
7. With a neat diagram explain the I-Q modulator and demodulator.
8. Describe the functions of MPSK
9. Explain the principle of optimum receiver used in WGN
10. Explain in detail the characteristics of Rayleigh channel.
11. Derive the probability of error for DPSK signaling scheme.
12. Briefly explain any one of the carrier synchronization techniques.
13. Explain about Carrier Synchronization & Symbol Synchronization.
14. Explain in detail the characteristics of Rician channel.

Equalization Techniques

Unit II
Part A :
1. State Nyquist pulse shaping criterion for zero ISI.
2. Write down the transfer function H(f) for an raised cosine filter.
3. Mention the application of eye pattern..
4. What is meant by correlative coding?
5. What are the causes for ISI?
6. What is a multi dimensional signal? Give an example.
7. What is ZFE ? Enumerate its features ?
8. State Nyquist criterion . What does it signify ?
9. State Shannon’s channel capacity theorem ?
10. Enumerate the significance of adaptive equalization algorithm.
11. Draw the block diagram of linear equalizer.
12. Compare decision feedback equalization and adaptive equalization algorithm.
13. Compare linear equalization and decision feedback equalization.
14. Give one example where adaptive equalization is required.
15. What is an eye pattern?
16. What is a DFE?
17. What is a band limited channel?
18. What are the methods used to suppress the ISI?
19. Define ISI and list at least two mitigation methods.
20. Mathematically express the Nyquist Criterion in frequency domain for pulse shaping to realize ISI free transmission

Part B :
1. Explain the error probability of BPSK , Viterbi algorithm and Turbo coding.
2. Derive the decision rule for optimum demodulation of digital signal in the presence of IS I and AWGN.
3. What is ISI in communication channels ? Explain a method to suppress ISI.
4. Define and explain the parameters of eye diagram . Mention its usage in digital communication systems. How it is used to know the information about a channel.
5. a)What is a transversal equalizer ? Explain how can it be implemented .
b)Explain the concept of LMS equalizer with a neat diagram . Mention its applications. Prepared by K K VEC/ECE/QB/ME/I/CS/CU7102/ADCT/2014-2015/ODD
6. Explain the need for equalization. Explain different types of equalization techniques.Compare the equalization techniques.
7. Explain duobinary signaling scheme without and with precoder for controlled ISI
8.Write short notes on :
i) LE-ZF ii). DFE – ZF iii) DFE iv) Adaptive equalization algorithm. v) Raised cosine
9. Derive the minimum mean squared error for zero forcing decision feedback equalizer (DFE-ZF)
10. Derive the transfer function and impulse response of duobinary systems which is used to control the ISI with appropriate diagram.
11. Explain about bandlimited channel with a neat block diagram.
12. The binary data 001101001 are applied to the input of duobinary system. Find the received output under the case without precoder and with precoder. Suppose the bit at second place is decoded erroneously construct the receiver output for the two cases.

Block Coded Digital Communication

Unit III
Part A :
1. State Shannon’s channel capacity theorem ?
2. What are the advantages and applications of Hamming codes ?
3. What is Golay code? What is extended Golay code?
4. What are the parameters affecting the performance of block coded communication system?
5. Draw the waveform representation of antipodal and orthogonal signals.
6. Mention the significance of trans-orthogonal code.
7. State Shannon’s channel coding theorem.
8. Mention the infinite bandwidth Shannon Information transport limit.
9. A single sided bandwidth of a modem is 3.4 kHz. Calculate the channel capacity for the signal to noise ratio of 30dB.
10. A channel with a 1 mhz bandwidth has snr of 63. What is the bit rate and signal level?
11. Find the channel capacity using Shanno’s formula. The spectrum of a channel is between 3 MHz and 4 MHz and SNR dB = 24 dB.
12. What is free distance and coding gain?
13. Mention any four application of Spread spectrum communication.
14. Find out whether the given PN sequence {00 11101}is ML sequence or not?
15. When the PN sequence is called ML sequence?
16. Define LBC. When a LBC is called cyclic code?
17. When a (n,k) linear block code is called Hamming code?If the minimum hamming distance of a (n,k) linear block code is 3, then what is its minimum Hamming weight. And find out the hamming weight of the codes 101010 and 010101.
18. Mention properties of cyclic code. What are two fundamental properties of cyclic code?
19. What is RS code?For a 8 bit RS codes, determinethe block length,n.
20. Give the error detection and error correction capability of Hamming code.

Part B :
1. Design a linear block code with a minimum distance of 3 and a message block size of 8 bits.
2. What is the basic concept of spread spectrum communication? Explain about FH – SS and DS-SS in detail with suitable diagram.
3. Derive the channel capacity for AWGN channel and the same for spread spectrum Communication if jamming margin is large.
4. What is a matched filter? Explain the different properties of it.
5. i) Differentiate cyclic codes from convolutional codes. ii) With a suitable example explain the Hamming and cyclic codes.
6. Explain about the architecture of coded digital communication system in detail.
7. Explain the architecture and performance of biorthogonal and transorthogonal codes in digital communication system.
8. a)Explain the architecture and performance of binary block codes with suitable example.
b) Explain the error detecting and correcting capabilities of linear block code.
9. With a neat diagram, explain Reed-solomon encoding and decoding circuit. Discuss advantages disadvantages and application of the code.
10. a)Derive the expression for relating the matched filter theory to the channel capacity
b) The parity check bits of a (8,4) block code are generated by, C5 = d1+ d2+ d4 , C6 = d1+ d2+ d3, C7 = d1+ d3+ d4 and C8 = d2+ d3+ d4 where d1, d2, d3 and d4 are message bits.
1. Find the G and P matrix for this code.
2. List all code vectors.
3. Find all errors detecting and correcting capabilities of this code.
4. Show that this code detects up to 3 errors only with suitable example.
11. For a (6, 3) code, generator matrix G is 100101; 010011; 001110. For all possible data words, find the corresponding code words and verify that the code is single error correcting code. Write the syndrome vector for the error pattern 000100.
12. The generator polynomial of a cyclic code is G(p) = P3 + P2 + 1. Find all the code vector for the code in non-systematic and systematic form. Draw the encoder and syndrome calculator. Also code the message vector 1000 and find the syndrome for the encoded message.