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Code No: 56026 :2: Set No. 2
II Fill in the blanks
11. The source coding efficiency can be increased by using _______________________
12. The advantage of Spread Spectrum Modulation schemes over other modulations is
_________________
13. Entropy coding is a _____________________
14. A convolutional encoder of code rate 1/2 is a 3 stage shift register with a message word
length of 6.The code word length obtained from the encoder ( in bits) is
_____________
15. Relative to Hard decision decoding, soft decision decoding results in _____________
16. If T is the code vector and H is the Parity check Matrix of a Linear Block code, then the
code is defined by the set of all code vectors for which H T .T = ______________
17. The advantage of CDMA over Frequency hopping is ____________
18. The Parity check matrix of a linear block code is
1 0 1 1 0 0
0 1 1 0 1 0
1 1 0 0 0 1
Its Hamming distance is ___________________
19. The significance of PN sequence in CDMA is ________________
20. The cascade of two Binary Symmetric Channels is a __________________________
-oOo-
Code No: 56026 Set No. 3
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 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
2. 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
3. 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%
4. 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)
5. 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
6. Information rate of a source is [ ]