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DCS MID - II Set A

This document contains a midterm exam for a Digital Communication Systems course taken by a student at Aditya College of Engineering. The exam tests the student's knowledge of key concepts through multiple choice questions, matching, fill-in-the-blank, and descriptive questions. Specifically, it covers topics like coherent vs. non-coherent modulation techniques, signal constellations, error correction codes, interleaving, and modulation schemes like BPSK, QPSK, FSK. The student is asked to answer questions testing their understanding of these fundamental digital communication topics.

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44 views2 pages

DCS MID - II Set A

This document contains a midterm exam for a Digital Communication Systems course taken by a student at Aditya College of Engineering. The exam tests the student's knowledge of key concepts through multiple choice questions, matching, fill-in-the-blank, and descriptive questions. Specifically, it covers topics like coherent vs. non-coherent modulation techniques, signal constellations, error correction codes, interleaving, and modulation schemes like BPSK, QPSK, FSK. The student is asked to answer questions testing their understanding of these fundamental digital communication topics.

Uploaded by

N.RAMAKUMAR
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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ADITYA COLLEGE OF ENGINEERING

Punganur Road, Madanapalle – 517325 SET A


BRANCH: ECE III-B.Tech (R15) I Sem -II MID EXAMINATIONS – NOV 2017 Duration: 20 Min.
SUBJECT & Code: Digital Communication Systems-15A04502 Type: Objective
Regd. No: Max. Marks: 10

Answer All questions. 4 x 1= 4

1. Compare coherent and non coherent modulation techniques?


2. Draw the signal constellation diagram of 8 PSK?
3. Define constraint length and code rate?
4. What is interleaving?

Match the following. 6x0.5=3

1. 10110010 a. Odd Parity [ ]


2. 00 & 1800 Phase Shift b. Hamming Distance [ ]
3. [PT | I n-k] c. ARQ systems [ ]
4. NACK d. More Delay [ ]
5. Error Detection e. BPSK [ ]
6. d(Ci,Cj) f. Even Parity [ ]

g. BFSK h. Parity check matrix H

Fill in the blanks. 3x0.5=1.5

7. Expand ARQ _________________________________________________.

8. The process of finding the position where an error occurred is called _________________.

9. For a (6,3) linear block code, the number of check bits required is _________________.

Choose the correct Answer. 3x0.5=1.5

10. What is the bandwidth of QPSK [ ]


a. Fb b. 2Fb c. Fb/2 d. 3Fb

11. In a code word, the condition to find the maximum number of errors that can be detected is
__________. [ ]
a. dmin=l+1 b. dmin=2t+1 c. d min=l2 d. None

12. The process of representing two different carrier phase for two different binary symbols is called
_____________________Technique. [ ]
a. QPSK b. BPSK c. BFSK d. DPSK
ADITYA COLLEGE OF ENGINEERING
Punganur Road, Madanapalle – 517325 SET A
BRANCH: ECE III-B.Tech (R15) I Sem - II MID EXAMINATIONS –NOV 2017 Duration: 90 Min.
SUBJECT & Code: Digital Communication Systems & 15A04502 Type: Descriptive
Regd. No: Max. Marks: 30

Note:- Answer one question from each Part and Q.1 is Compulsory.

1. (a) Draw the block diagram of pass band data transmission?


(b) Find an encoded and decoded sequence for message sequence 10101 for DPSK system.
(c) Explain the Viterbi algorithm?
(d) Explain in brief about Burst errors?
(e) Find the impulse response for given convolution encoder circuit.

PART-A

2. a. Explain correlation receiver with neat block diagram? [4]


b. Explain the Gram Schmidt orthogonalization process in band pass digital transmission? [6]

3. a. Explain the coherent detection of signals in noise? [4]


b. Explain the generation and detection of coherent BFSK? Derive an expression of probability of
error? [6]

PART-B

4. a. Explain the generation and detection of QAM? Derive an expression of probability of error? [6]
b. Explain the operation of DPSK in brief with neat block diagrams? [4]

5. a. Consider a (6,3) systematic linear block code, the three parity check digits C4, C5 and C6 are
C4=d1+d2+d3, C5=d1+d2 and C6=d1+d3. Construct the appropriate generator matrix for this code
and find all possible code vectors? [6]
b. Explain FEC system in detail? [4]

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