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Code No: 07A5EC09 Set No. 3
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
III B.Tech. I Sem., II Mid-Term Examinations, November – 2010
DIGITAL COMMUNICATIONS
Objective Exam
Name: ______________________________ Hall Ticket No.
Answer All Questions. All Questions Carry Equal Marks.Time: 20 Min. Marks: 20.
I Choose the correct alternative:
1) Which of the following is a p(Y/X) matrix for a binary symmetric channel [ ]
a) b) c) d) None
2) Exchange between channel bandwidth and (S/N) ratio can be adjusted based on [ ]
a) Shannon’s limit b )Shanon’s source coding
c) Shannon’s channel coding d) Shannon Hartley theorem
3) For the data word 1110 in a (7, 4) non-systematic cyclic code with the generator
polynomial 1+x+x 3 , the code polynomial is [ ]
a) 1+x+x 3 +x 5 b) 1+x 2 +x 3 +x 5 c) 1+x 2 +x 3 +x 4 d) 1+x 4 +x 5
4) A source X with entropy 2 bits/message is connected to the receiver Y through a noise free
channel. The conditional probability of the source is H(X/Y) and the joint entropy of
the source and the receiver H(X, Y). Then [ ]
a) H(X,Y)= 2 bits/message b) H(X/Y)= 2 bits/message
c) H(X, Y)= 0 bits/message d) H(X/Y)= 1 bit/message
5) Which of the following is a p(Y/X) matrix for a binary Erasure channel [ ]
a) 11ppqq−⎡⎤⎢⎥−⎣⎦ b) c) d) None
6) The channel matrix of a noiseless channel [ ]
a)consists of a single nonzero number in each column.
b) consists of a single nonzero number in each row.
c) is an Identity Matrix. d) is a square matrix.
7 ) Information content of a message [ ]
a) increase with its certainty of occurrence. b) independent of the certainty of
occurrence.
c) increases with its uncertainty of occurrence. d) is the logarithm of its uncertainty of
occurrence.
8) The channel capacity of a BSC with the transition probability ½ is [ ]
a) 0 bits b) 1 bit c) 2 bits d) infinity
9) For the data word 1110 in a (7, 4) non-systematic cyclic code with the generator
polynomial 1+x 2 +x 3 , the code polynomial is [ ]
a) 1+x+x 3 +x 5 b) 1+x 2 +x 3 +x 5 c) 1+x 2 +x 3 +x 4 d) 1+x+x 5 Cont…..2