Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 6th Semester (Sixth Semester) 2015-2016 NEC 602EEC 601 Digital Communication Question Paper
(Following Paper ID and Roll No. to be ?lled in your
Answer Books)
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B.TECH.
Theory Examination (Semester-VI) 2015-16
DIGITAL COMMUNICATION
?ne : 3 Hours Max. Marks : 100
Section-A
Q.l. Attempt all parts. All parts carry equal marks. Write
answer of each part inshort. (2X10=20)
(3) Draw the Block diagram of digital receiver.
(b) Why the pulse shaping is more direct and potent feature
in terms of shaping the PSD?
(c) Binary data at 9600 bits/s are transmitted using 8?ary
PAM modulation with a system using a raised cosine
roll?o?? ?lter characteristics. The system has a frequency
.response out to 2.4 kHz. Calculate symbol rate and roll
o?? ?actor.
(l) P.T.O.
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(d) Justify that ISI is not noise.
(e) De?ne the Commutative distribution function (GDP).
(1) A high resolution black & white pictures comist of about
2? 106 picture elements & l6 di??erent brightness levels.
Pictures are repeated at the rate of 32 per see. All
picture elements are assumed to be independent & all
levels have equal likelihood of occurrence. Calcuhte the
average rate of information conveyed by this TV picture
source.
(g) Explain the importance of probability of error.
(h) Why the Matched ?lter is optimum ?lter?
(1) How the spread spectrum system is di??erent ?'om
conventional modulation system?
(i) What is manchester coding?
Section-B
Q2. Attempt any ?ve questions from this section.
(lOXS=50)
(a) List the properties of line coding.
- (2)
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(b)
(C)
(d)
Draw the following data formats for the data bit stream
1100110.
(i) Unipolar RZ
(iDAMI
(iii) NRZ(M)
With the help of block diagram, explain QPSK coherent
digital cam'er system. Sketch the QPSK waveform for
the sequence 1 101010010, assuming the carrier
frequency to be equal to the bit rate.
Why the Gaussian distnbution is widely used in
Communication?
In an experiment, a trial consists of 4 successive
tosses of a coin. If we de?ne a Random Variable X
as the number of heads appearing in a trial, determine
Px(x) and Fx(x).
Show that impulse response of a matched ?lter is
proportional to an inverted and shi?ed version of the
input signal to which ?lter is matched.
Draw the block diagram of DSSS system and explain
the importance of PN sequence in D888.
(3) P.T.O.
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(f) Wn?te short notes on
(1) MUD
(ii) OFDM.
(g) De?ne and list the propeities of Autocorrehtion. Show
that the random process X(t)=A cos(coct+9), where 9 is
a random variable uniformly distributed in the range
(0,21t) is a wide sense stationary process.
(h) A binary source produces 0?s and 1?s independemly with
probabilities P(0)=O.2 and P(l)=0.8. The binary data is
thentransmitted over anoisy channel. The probability of
correct reception when a ?0? has been transmitted is 0.9
and the probabilityofemneous receptionwhen ?1? has
been transmitted is 0.2.
(i) Find the probabilities of erroneous reception when
a ?0? is transmitted and probability of correct
reception when a ?1? was transmitted.
(in) Find the over all probability of receiving a ?0? and
a ?1,
(iii) If a ?l ? is received, what is the probability that a
?0? was transmitted.
(4)
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Section-C
Note: Attempt any two questions from this section.
Q3.
Q4.
(15X2=30)
(a) De?ne the entropy of a discrete memoryless source
emittinngymbobanddiscmmthepropatiesofmtropy
(b) A zero memory source emits six messages with
probabilities 0.3, 0.25, 0.15, 0.12, 0.10, 0.08.
Find 4-ary (Quaternary) Hu?inan code. Determine its
average word length, the ef?ciency and the redundancy.
What is hamming distance? Using hamming bound condition
explain hamming code.
A parity code has the parity check manix
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OHO
t-?OO
(a) Determine the generator matrix G
(b) Find the code word that begins with 101 .........
(5) P.T.0.
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(0) Suppose that the receivedoodewond is 110110. Decode
this received word.
QS. List the advanatges of cyclic codes over hamming
codes.Construct the systematic (7,4) cyclic code using the
generator polynomial g(x) = x?+x+1. What are the error
correcting capabilities of this code? Construct the decoding
table. If the received word is 1101100, determine the
transmitted data word.
(5)
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This post was last modified on 29 January 2020