Mumbai University Previous year question papers Digital Communication June 2007

Mumbai University Previous year question papers

VI Sem Electronics Examination June 2007

Digital Communication

N.S.: (1) Question No.1 is compulsory.

(2) Attempt any four questions from Q. Nos. 2 to 7.


1. Answer the following questions in brief:

(i) Basebandmodulated signal is differentthan carriermodulated signal. Compare

the two Corelative coding is used for partial re~ponse signaling. Why?

iii) Channel coding technique is different from source coding. How?

(iv) COMA transmission uses spread spectrum signal. Justify.

(v) BPSK transmission is coherent transmission. Justify.


2. Explain the modulation scheme for the following carrier modulated sign§ils :

(i) apSK signal (iii) BFSK signal

ii) MSK signal (iv) Spread spectrum signal.


3. Explain the following questions with proper illustration:

(i) In DEPSK transmission, error always exist in pairs.

(ii) BFSK transmission can be orthogonal or non-orthogonal.

(iii) Phase continuity is maintained in MSK-signal.


4. Derive the following relationships:

(i) PSD of apSK signal.

(ii) Eucledian distance of non-orthogonal BFSK signal.

(iii) Nyquist rate for PCM signal.


5. Consider the binary bit stream 110110100010, draw the following waveforms:

(i) Baseband signal in NR2, Manchester and polar RZ format.

(ii) Carrier modulated signal in BPSK, QPSK and MSK signal format.

(iii) (7, 4) blockcodedBPSKsignal.


6. (a) Explain FHSS technique with the help of block diagram and signal frequency spectrum.

(b) Defina the following terms:

(i) Systematic and non-systematic code

(ii) Hamming weight and Hamming distance

(iii)” Entropy and redundancy

(iv). Code rate.


7. Write short notes on any two:

(i) ISS and ICI

(ii) Eye diagram

(iii) Trellis diagram.

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