1. Alternate Mark Inversion (AMI) is also known as
Correct : A. pseudo ternary coding
2. The process of coding multiplexer output into electrical pulses or waveforms for transmission is called
Correct : A. line coding
3. Eye pattern is
Correct : D. all of the above
4. The criterion used for pulse shaping to avoid ISI is
Correct : A. nyquist criterion
5. TDM is
Correct : B. digital multiplexing
6. Random variables give relationship between _
Correct : C. random event and a real number
7. The distribution function of random variable is
Correct : A. p(x less than or equal to x)
8. The value of the probability density function of random variable is
Correct : A. positive function
9. Which gives the measure of randomness of the random variable?
Correct : B. variance
10. Random process is a function of
Correct : A. random event and time
11. A random process is called as stationary in strict sense if
Correct : A. its statistics vary with shift in time origin
12. For a stationary process, autocorrelation function depends on
Correct : B. time difference
13. The autocorrelation function is maximum at
Correct : A. origin
14. Standard deviation is _
Correct : B. rms value or ac
15. The average power of white noise is
Correct : C. infinity
16. he distribution function of -(infinity) and (infinity) is
Correct : A. 0 and 1
17. White noise has mean and _ variance.
Correct : C. zero and finite
18. Power spectral density function is a?
Correct : D. all of the mentioned
19. Energy spectral density defines
Correct : B. signal energy per unit bandwidth
20. Power spectrum describes distribution of under frequency domain.
Correct : B. variance
21. How can power spectral density of non periodic signal be calculated?
Correct : B. by truncating
22. What is Wiener-Khinchin theorem?
Correct : B. spectral density and auto-correlatioon makes a fourier transform pair
23. According to Parseval’s theorem the energy spectral density curve is equal to?
Correct : B. area under square of the magnitude of the signal
24. Autocorrelation is a function which matches
Correct : C. one signal with its delayed version
25. Autocorrelation is a function of
Correct : C. time difference
26. Autocorrelation is maximum at
Correct : B. origin
27. Autocorrelation function of periodic signal is equal to
Correct : B. power of the signal
28. Autocorrelation function of white noise will have?
Correct : A. strong peak
29. Thermal noise in the communication system due to thermal electrons
Correct : B. cannot be eliminated
30. White noise has power spectral density.
Correct : A. constant
31. The average noise power of white noise is
Correct : B. infinity
32. The channel may be affected by
Correct : C. thermal noise & interference from other signals
33. In Random Variable we have
Correct : C. sample space & sample points
34. In Random Process we have
Correct : D. sample function & ensemble of sample function
35. The detection method where carrier’s phase is given importance is called as
Correct : A. coherent detection
36. The coherent modulation techniques are
Correct : D. all of the mentioned
37. The real part of a sinusoid carrier wave is called as
Correct : A. inphase
38. The FSK signal which has a gentle shift from one frequency level to another is called as
Correct : B. continuous psk
39. Which modulation scheme is also called as on-off keying method?
Correct : A. ask
40. In differential PSK the date is
Correct : A. encoded differentially
41. Envelope detector consists of
Correct : B. rectifier and low pass filter
42. M-ary signaling produces error performance with orthogonal signaling and error performance with multiple phase signalling.
Correct : B. improved, degraded
43. Which is more vulnerable to noise?
Correct : B. 4-ary system
44. In which system, bit stream is portioned into even and odd stream?
Correct : C. qpsk
45. The error performance of MPSK as M or k increases.
Correct : B. decreases
46. In MPSK adding new signals make it vulnerable to noise and in MFSK make it vulnerable.
Correct : A. does, does not
47. In orthogonal signalling with symbols containing more number of bits we need power.
Correct : A. more
48. Energy per symbol Es is given as
Correct : A. es=eb(log2m)
49. The relation between the probability of bit error and probability of symbol error in M-ary orthogonal signalling is
Correct : C. (m/2)/m-1
50. Performance of BFSK signal is than BPSK.
Correct : A. 3db worse
51. The non coherent FSK needs Eb/N0 than coherent FSK.
Correct : A. 1db more
52. The DPSK needs Eb/N0 than BPSK.
Correct : A. 1db more
53. Which is easier to implement and is preferred?
Correct : B. non coherent system
54. Which is the main system consideration?
Correct : D. all of the mentioned
55. In the frequency of the carrier signal is varied based on the information in an a digital signal
Correct : C. fsk
56. In the amplitude of the carrier signal is varied based on the information in an a digital signal
Correct : A. ask
57. In modulation , the bit rate is 8 times the baud rate
Correct : C. 256-qam
58. In modulation , the baud rate is 1/4 times the bit rate
Correct : D. none of above
59. Which of the following is not a characteristic of PN sequence?
Correct : D. non deterministic
60. symbols.
Correct : D. 2m-1
61. PN sequence can be generated using .
Correct : A. sequential logic circuits
62. DSSS system spreads the baseband signal by the baseband pulses with a pseudo noise sequence.
Correct : C. multiplying
63. Frequency hopping involves a periodic change of transmission
Correct : B. frequency
64. What is the set of possible carrier frequencies in FH-SS?
Correct : A. hopset
65. The bandwidth of the channel used in the hopset is called
Correct : C. instantaneous bandwidth
66. The processing gain of FH systems is given by ratio of
Correct : D. total hopping bandwidth and instantaneous bandwidth
67. Pseudorandom signal predicted.
Correct : A. can be
68. In FH-SS which of the following Modulation Demodulation Technique has been used
Correct : B. fsk
69. In DS-SS which of the following Modulation Demodulation Technique has been used
Correct : A. bpsk
70. Frequency division multiple access (FDMA) assigns channels to users.
Correct : A. individual, individual
71. The FDMA channel carries phone circuit at a time.
Correct : C. one
72. The bandwidth of FDMA channel is
Correct : B. narrow
73. The symbol time in FDMA systems is thus intersymbol interference is
Correct : D. large, low
74. Due to transmission scheme bits are needed for overhead in FDMA systems.
Correct : A. continuous, few
75. is based on FDMA/FDD.
Correct : D. amps
76. Which of the following is not true for TDMA?
Correct : A. single carrier frequency for single user
77. Because of transmissions in TDMA, the handoff process in
Correct : D. discontinuous, simple
78. synchronization overhead is required in TDMA due to transmission.
Correct : A. high, burst
79. of TDMA system is a measure of the percentage of transmitted data that contains information as opposed to providing overhead for the access scheme.
Correct : A. efficiency
80. A TDMA system uses 25 MHz for the forward link, which is broken into radio channels of 200 kHz. If 8 speech channels are supported on a single radio channel, how many simultaneous users can be accommodated?
Correct : D. 1000
81. US digital cellular system based on CDMA was standardized as