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Code No: 56026 Set No. 4
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
III B.Tech. II Sem., II Mid-Term Examinations, April – 2012
DIGITAL COMMUNICATIONS
Objective Exam
Name: ______________________________ Hall Ticket No.
Answer All Questions. All Questions Carry Equal Marks.Time: 20 Min. Marks: 10.
I Choose the correct alternative:
1. A source emits messages A and B with probability 0.8 and 0.2 respectively. The
redundancy provided by the optimum source-coding scheme for the above Source is [
]
A) 27% B) 72% C) 55% D) 45%
2. A source X and the receiver Y are connected by a noise free channel. Its capacity is [ ]
A) Max H(Y/X) B) Max H(X) C) Max H(X/Y) D) Max H(X,Y)
3. Exchange between Band width and Signal noise ratio can be justified based on [ ]
A) Hartley - Shanon‘s Law B) Shanon‘s source coding Theorem
C) Shanon‘s limit D) Shanon‘s channel coding Theorem
4. Information rate of a source is [ ]
A) maximum when the source is continuous B) the entropy of the source measured in
bits/message
C) a measure of the uncertainty of the communication system
D) the entropy of the source measured in bits/sec.
5. The Hamming Weight of the (6,3) Linear Block coded word 101011 [ ]
A) 5 B) 4 C) 2 D) 3
6. Which of the following can be the generating polynomial for a (7,4) systematic Cyclic
code? [ ]
A) x 3 +x+1 B) x 5 +x 2 +1 C) x 4 +x 3 +1 D) x 7 +x 4 +x 3 +1
7. In a Linear Block code [ ]
A) the received power varies linearly with that of the transmitted power
B) parity bits of the code word are the linear combination of the message bits
C) the communication channel is a linear system
D) the encoder satisfies super position principle
8. The fundamental limit on the average number of bits/source symbol is [ ]
A) Mutual Information B) Channel capacity
C) Information content of the message D) Entropy of the source
9. A system has a band width of 3KHz and an S/N ratio of 29dB at the input of the receiver.
If the band width of the channel gets doubled, then [ ]
A) its capacity gets halved B) the corresponding S/N ratio gets doubled
C) the corresponding S/N ratio gets halved D) its capacity gets doubled
10. 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 a square Matrix
D) is an Identity Matrix
Cont…….2