B.TechSemester 62021-22Digital CommunicationKEC601
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Digital Communication (KEC601) - AKTU Question Paper 2021-22

B.Tech · Semester 6 · Free PDF Download

This is the official AKTU Digital Communication Previous Year Question Paper for B.Tech Semester 6, academic session 2021-22. Published by Dr. A.P.J. Abdul Kalam Technical University (AKTU/UPTU), Lucknow. Free PDF download — no login required.

Course:B.Tech
Semester:Semester 6
Session:2021-22
University:AKTU / UPTU

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Questions Asked in 2021-22

Digital Communication (KEC601) — complete question paper

Section AAttempt All of the following Questions in brief Marks(10X2=20) CO
  • a
    A die is thrown. Determine the probability that an even number comes up. 1
  • b
    Define random variable. 1
  • c
    Briefly explain inter symbol interference. 2
  • d
    Draw waveform for NRZ- unipolar code for 101101. 2
  • e
    For an ideal binary ASK, data is transmitted with 64kbps, find the bandwidth. 3
  • f
    Discuss the application of ASK modulation. 3
  • g
    Briefly explain any one property of a matched filter. 4
  • h
    Define bit error rate. 4 Q1(i) Briefly explain information. 5 Q1(j) Find the entropy for three messages with their probabilities ½, ¼ and 1/4 respectively
Section BAttempt ANY THREE of the following Questions Marks (3X10=30) CO
  • a
    The probability density function is given as fxxaeb| x| , where X is a random variable, whose allowable values range from x ∞to x ∞. Find: i) Relationship between a and b ii) Autocorrelation
  • b
    Write Short Notes on any two of the following: i) Various NRZ line coding of data 11001101 ii) Eye diagram iii) Gram-Schmidt orthogonalization procedure
  • c
    Explain the PSK modulation and de modulation with suitable block diagram and waveforms. Compare the BPSK system with DPSK system
  • d
    Describe matched filter with suitable diagram? Prove that impul se response of a matched filter is proportional to a shifted version of the input signal to which filter is matched?
  • e
    Define entropy and mutual informa tion? Prove the relationship b etween differen t entropies
Section CAttempt ANY ONE following Question Marks (1X10=10) CO
  • a
    Differentiate between wide sense stationary and strict sense st ationary rando m processes? Find the mean and variance of the sum of two random variables if th e mean of one of the two random variables is zero. Assume the ran dom variables as per convenience
  • b
    Discuss Gaussian random process with central limit theorem alon g with a suitable example and diagram
Section CAttempt ANY ONE following Question Marks (1X10=10) CO
  • a
    Explain the function of scrambler and descrambler with neat blo ck diagram. Give an example with a sequence generated
  • b
    Draw and explain function of each block in digital communicatio n system. Also state the need of pulse shaping
Section CAttempt ANY ONE following Question Marks (1X10=10) CO
  • a
    How does the QPSK modulator transmit digital data over channel ? Also explain the demodulation process of the QPSK modulated signal from an ideal channel
  • b
    Explain QAM system with suitable block diagram and constellation diagram. 3
Section CAttempt ANY ONE following Question Marks (1X10=10) CO
  • a
    Derive the expression for proba bility of error in FSK modulatio n system. Mention all the assumed parameters clearly. Why is it better than ASK?
  • b
    Describe the spread spectrum modulation with FHSS and DSSS. 4
Section CAttempt ANY ONE following Question Marks (1X10=10) CO
  • a
    The parity check matrix of a particular (7,4) linear block code is given by: i) Find the generator matrix (G). ii) List all the code vectors. iii) What is the minimum distance between code vectors?
  • b
    Construct Huffman codes for five messages m 1, m 2, m 3, m 4 and m 5 with probabilities 0.0625,0.125,0.25, 0.0625 and 0.5, respectively. Calculate the entropy and average length of the code. Also explain the procedure for finding the code

Question text is extracted from the official AKTU question paper PDF above. Hindi translations are omitted — every question is printed in English in the original paper. Last verified: 2026-08-23.

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