Mumbai University Previous year question papers Digital Communication June 2009

Mumbai University Previous year question papers

VI Sem Electronics Examination June 2009

Digital Communication


N.B~uestion No.1 is compulsory.

(2) Attempt any our questionsout of remainingsix questions.

(3) Assume suitable data ~herever necessary and justify it.

1.ttemptanyfour fromthe following:-

(a) Explain need for equalization in digital communication system.

(b) Tamed FM

(c) The error function

(d) 151and.ICI.


2.(a) Explain the central limit theorem for random variables.

(b) Explain in brief :-


i) Stationary and Non-stationary process.

(ii) Wide sence stationary process.

(iiii) Ergodic process.


3. Explain in detail 16-QAMTransmitterand receiver system. Also draw signal.constellation diagram for 16 QAM in detail.


4. (a) Distinguishbetween ‘Matched Filter’ and ‘Correlator’. How are they related to each other.

(b) Explainthe principleand working of FHSS in detail. Differentiatebetween frequency hopping and fast frequency hopping.


5. (a) Explain the concept of ICpartialresponse signaling”. What is the advantage of this type of signaling?

(b) Drawthe block diagramof a duobinarypartial responsesignaling system and explain its working.



6. The generator polynomial for a (7, 4) cyclic code is g(x) = 1 + x + x3

(a) Drawthe block diagramsof an encoder and syndromes calculatorfor thin code.

,(b) Find the,code polynomial for message vector (0 1 0 1).

(c) Assume ~hatthe first bit of the code vector for the messagevector in (b) suffers transmission error. Find syndrome at the receiver.


7. (a) For the convolutional encoder shown below sketch the code tree.~o.h12y,

(b) Write short notes on :

(i) Viterbi’s algorithm

(ii) Compare coded and uncoded system.


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