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Code No: 07A5EC09 :2: Set No.3
10) A source transmitting ‘m’ number of messages is connected to a noise free channel. The
capacity of the channel is [ ]
a) m bits/symbol b) m 2 bits/symbol c) log m bits/symbol d) 2m bits/symbol
II Fill in the blanks:
11) Assuming 26 characters are equally likely , the average of the information content of
English language in bits/character is________________
12) The distance between two vector c1 and c2 is defined as the no.of components in which
they are differ is called as____________________
13) The minimum distance of a linear block code is equal to____________________of any
non-zero code word in the code.
14) A linear block code with a minimum distance d min
can detect upto ___________________
15) For a Linear Block code Code rate =_________________
16) The information rate of a source is also referred to as entropy measured in
______________
17) H(X,Y)=______________ or __________________
18) Capacity of a noise free channel is _________________
19) The Shanon’s limit is ______________
20) The channel capacity with infinite bandwidth is not because ____________
-oOo-
Code No: 07A5EC09 Set No. 4
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) 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
2) 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
3) Which of the following is a p(Y/X) matrix for a binary Erasure channel [ ]
a) 11ppqq−⎡⎤⎢⎥−⎣⎦ b) c) d) None
4) 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.
5) 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.
6) The channel capacity of a BSC with the transition probability ½ is [ ]