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Digital Communications MCQs set-8
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1. Orthogonal vectors are
Perpendicular to each other
Their dot product must be zero
One signal cannot interfere with the other
All of the mentioned
2. In orthogonal signalling as k increase there is
Improved error performance
Degraded error performance
Improved bandwidth
None of the mentioned
3. In non orthogonal signalling as k increases there is
Degraded error performance
Improved bandwidth efficiency
Increase in required Eb/N0
All of the mentioned
4. In orthogonal signal, all cross correlation coefficients are
One
Zero
Negative
None of the mentioned
5. The smaller the cross correlation, the ______ is the distance between the signal vectors.
More
Less
Double
Half
6. Biorthogonal set consists of
Orthogonal signals
Antipodal signals
Combination of orthogonal and antipodal
None of the mentioned
7. Which codes perform better?
Orthogonal
Biorthogonal
Orthogonal & Biorthogonal
None of the mentioned
8. Biorthogonal codes needs ________ bandwidth as orthogonal codes.
Equal
Double
Half
Triple
9. Transorthogonal code is obtained by
Deleting last digit of each orthogonal codeword
Deleting first digit of each orthogonal codeword
Doubling each digit of orthogonal codeword
Taking negative of each digit of orthogonal codeword
10. Which code requires minimum Eb/N0?
Orthogonal
Biorthogonal
Simplex
All of the mentioned
11. In binary symmetric channel, in the demodulator _____ decision is made.
Hard
Soft
Hard & Soft
None of the mentioned
12. In Gaussian channel demodulator ______ decision is made.
Hard
Soft
Hard & Soft
None of the mentioned
13. Which decoders are less complex?
Soft decision decoder
Hard decision decoder
Hard & Soft decision decoder
None of the mentioned
14. The ratio of redundant bits to data bits is called as
Code rate
Redundancy rate
Symbol rate
Transmission rate
15. If the parity bit takes value one then the summation of code-word gives
Even result
Odd result
Even & Odd result
None of the mentioned
16. The summation operation is performed using _____ logical operation.
EX-OR
AND
OR
EX-NOR
17. The probability of message error is written as
Block error
Word error
Block & Word error
None of the mentioned
18. In a real time communication system addition of redundant bits leads to
More bandwidth requirement
Faster rate of transmission
More bandwidth requirement & Faster rate of transmission
None of the mentioned
19. Coding gain is defined as
Reduction in Eb/N0
Increase in Eb/N0
Same as Eb/N0
None of the mentioned
20. The capacity per cell is ______ Eb/N0.
Directly proportional
Inversely proportional
Double the
Half the
21. Hamming distance can be given by the number of elements in which
They are same
They differ
Which are non zero
None of the mentioned
22. Code strength is characterized by its
Minimum distance
Maximum distance
Code weight
Code size
23. The distance between two code-words is equal to the _____ of the third code-word which is the sum of the first two code-words.
Size
Weight
Minimum distance
None of the mentioned
24. Error detecting capability is given as
Dmin + 1
Dmin -1
Dmin
Dmin/2
25. The minimum distance Dmin can also be given as
Dmin >= α + β + 1
Dmin <= α + β + 1
Dmin >= α + β – 1
Dmin <= α + β + 1
26. The number of errors that can be corrected without erasure information is
Dmin+1
Dmin – 1
(Dmin+1)/2
(Dmin – 1)/2
27. For better efficiency and simplicity, n should be
Maximum
Minimum
Zero
Infinity
28. Nyquist frequency is given by
fs
2fs
fs/2
none of the mentioned
29. Some various types of distortion are
Jitter
Noise
Aperture error
All of the mentioned
30. Noise which can affect sampling are
Thermal sensor noise
Analog circuit noise
Thermal sensor & Analog circuit noise
None of the mentioned
31. Oversampling can completely eliminate
Aperture error
Non linearity
Quantization error
All of the mentioned
32. Sampling can be used in
Audio
Speech
Video
All of the mentioned
33. What is the bit depth used for audio recording?
8 bit
16 bit
24 bit
All of the mentioned
34. Which factors are measured using the units of lines per picture height?
Resolution
Sampling rate
Resolution & Sampling rate
None of the mentioned
35. Sampling of simultaneously two different but related wave-forms is called as
Over sampling
Complex sampling
Inter sampling
None of the mentioned
36. Sampling can be done for functions varying in
Space
Time
Space & Time
None of the mentioned
37. Reconstruction of continuous signals is done using
Decimation algorithm
Interpolation algorithm
Decimation & Interpolation algorithm
None of the mentioned View Answer
38. The cyclic codes are designed using
Shift registers with feedback
Shift registers without feedback
Flipflops
None of the mentioned
39. A cyclic code can be generated using
Generator polynomial
Generator matrix
Generator polynomial & matrix
None of the mentioned
40. The feedback shift register circuit is called as
Multiplying circuit
Dividing circuit
Feedback circuit
Shifting circuit
41. In the dividing circuit, the parity polynomial is obtained by the
Quotient
Remainder
Dividend
Divisor
42. The received code contains an error if the syndrome vector is
Zero
Non zero
Infinity
None of the mentioned
43. Block codes are generated using
Generator polynomial
Generator matrix
Generator polynomial & matrix
None of the mentioned
44. Extended go-lay code is formed by
Adding overall parity bit to perfect go-lay code
Ex-oaring overall parity bit with perfect go-lay code
Ex-oaring each bit of go-lay code
Dividing the overall parity bit with perfect go-lay code
45. Block length is the _____________ in the code word.
Number of elements
Distance between elements
Number of parity bits
None of the mentioned
46. The rate of a block code is the ration of
Block length to message length
Message length to block length
Message weight to block length
None of the mentioned
47. Linear codes are used for
Forward error correction
Backward error correction
Forward error detection
Backward error detection
48. The k-bit message forms ____ distinct messages which is referred to as k-tuples.
2k
K2
2k
21/k
49. The sum of any two vectors in subset S is also in S. This is called as
Addition property
Subset property
Closure property
Similarity property
50. To avoid corruption during transmission, the code-word should be
Near
Far apart
Far
None of the mentioned
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