Computer Networks - Computer Networks Section 2

76. Phase shift keying (PSK.) method is used to modulate digital signals at 9600 bps using 16 levels. The line signals speed (i.e. modulation rate) will be

  • Option : A
  • Explanation : 9600 corresponds to bits per second and the level is 16. For a 16-PSK, given the baud rate N, the bit rate would be 4N. Here bps is provided which is 9600.
    In order to calculate the baud rate we have to divide bps/4, because the signal level is 16.So the answer would be 9600/4=2400 baud. Option is (A).
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77. Television channels are 6 MHz. How many bits can be sent if four level digital signals are used (assume a noiseless channel)?

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78. What is the maximum burst length on an 155.52 Mbps ATM ABR connection whose PCR value 200,000 and whose L value is 25 msec ?

  • Option : B
  • Explanation : Given : T = 5 μ sec
    L = 25 μ sec
    d = 2.73 μ sec.
    N = (1 + L) / (T - δ) = 12.01 i.e. 12 cells.
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79. Poll/select line discipline requires what to identify the packet recipient ?

  • Option : C
  • Explanation : In Poll / select method, every device on a link has an address that can be used for identification
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80. In sliding window flow control, if window size is 63, what is the range of sequence numbers ?

  • Option : A
  • Explanation : In sliding window flow control the window size is 63, the range of sequence numbers are 0 to 63 { 0.....63}.
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