Digital Communications Questions

7/23/2019 Digital Communications Questions

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DIGITAL COMMUNICATION

1. DIGITAL TRANSMISSION BASIC

a. Line coding - bi phase-s, bipolar rz, rz-ami, manchester, nrz-sb. PCM + block diagram

c. Block diagram of dcom and explain each block in detail**

d. SN on delta modulation

e. SN DPCM

f. Detailed note on Adaptive delta modulation. Explain how ADM overcomes

drawbacks of delta modulation

g. Differentiate between analog and digital communication

h. State and explain sampling theorem

i. Enumerate one type of errors in a delta modulation system

j. ADM block diagram

2. ENTROPY

a. Relation between information and entropy + properties of entropy**

b. Huffman and Shaanan fano to find code length, entropy, efficiency

c.d.

e.

3. BASE BAND SHAPING

a. Give significance of eye diagram

b. What is ISI and state its remedy + Derive and expression for ISI**

c. SN on equalisation

d. Explain Gram-Schmidt procedure

e. Derive Power spectra of unipolar, polar and bipolar NRZ

f. Nyquist criteria SN

g. Merits and demerits of passband transmission over baseband transmission

h. Elaborate the structure of adaptive equaliser

i. What are the shortcomings of delta modulation? How is it overcome by ADM?

Explain ADM

j.



4. DIGITAL MODULATION TECHNIQUES

a. Difference between coherent and non coherent**

b. Prove MSK is FSK. Draw waveforms of MSK

c. Binary FSK and find Euclidian distanced. State different types of QAM and prove for a 16-QAM digital modulation technique

the euclidian distance and draw constellation diagram

e. Draw waveform for ASK, FSK, PSK modulation if given data sequence is

10111001

f. Explain coherent detection

g. Explain DPSK

h. Explain modulation and demodulation in MSK + waveforms

i. Describe BPSK modulation and demodulation + signal space and PSD spectrum

j. Sketch QAM constellation diagram and evaluate euclidian distance

k.

5. BASEBAND DETECTION

a. SN correlation receiver**

b. Matched filter SN

c.

d.e.

6. ERROR CONTROL CODING

a. Define weight of a code word, code rate, code efficiency and hamming distance

b. Parity check matrix to find generator matrix, minimum distance between code

vectors, no. of errors, correction of errors

c. Convolution code

d. Hamming code numerical

e. SN on distance property of convolution

f. Derive the expression for probability of bit error

g. Explain Syndrome decoding with diagram

h. Design a convolution encoder - numerical

i. Generate systematic cyclic code - numerical



7. SPREAD SPECTRUM MODULATION

a. SN on pseudo noise sequence. Generate a sequence if seed point is 1001 **

b. SN spread spectrum techniques

c. SN frequency hop spectrumd.

e.

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Digital Communications Questions