Digital Communication - Study Mode
[#186] During transmission over a certain binary communication channel, bit errors occur independently with probability p. The probability of AT MOST one bit in error in a block of n bits is given by
Correct Answer
(C) np (1 - p) n - 1 + (1 - p) n
[#187] The message bit sequence to a DPSK modulator is 1, 1, 0, 0, 1, 1. The carrier phase during the reception of the first two message bits is π, π. The carrier phase for the remaining four message bits is
Correct Answer
(C) 0, π, π, π
[#188] A deterministic signal has the power spectrum given in figure. The minimum sampling rate needed to completely represent signal is
Correct Answer
(C) 3 kHz
[#189] In binary frequency shift keying (FSK), the given signal waveforms are u 0 (t) = 5cos(20000πt)
0 ≤ t ≤ 7 and u 1 (t) = 5cos(22000πt)
0 ≤ t ≤ T, where T is the bit-duration interval and t is in seconds. Both u 0 (t) and u 1 (t) are zero outside the interval 0 ≤ t ≤ T. With a matched filter
(correlator) based receiver, the smallest positive
value of T (in milliseconds) required to have u 0 (t) and u 1 (t) uncorrelated is
Correct Answer
(B) 0.5 ms
[#190] A source emits bit 0 with probability $$frac{1}{3}$$xa0 and bit 1 with probability $$frac{2}{3}.$$xa0 The emitted bits are communicated to the receiver. The receiver decides for either 0 or 1 based on the received value R. It is given that the conditional density functions of R as [x08egin{gathered}
{f_{R|0}}left( r
ight) = left{ {x08egin{array}{*{20}{c}}
{frac{1}{4},}&{ - 3 leqslant r leqslant 1} \
{0,}&{{ ext{otherwise
}}}
end{array}}
ight. hfill \
{f_{R|1}}left( r
ight) = left{ {x08egin{array}{*{20}{c}}
{frac{1}{6},}&{ - 1 leqslant r leqslant 5} \
{0,}&{{ ext{otherwise
}}}
end{array}}
ight. hfill \
end{gathered} ] The minimum decision error probability is
Correct Answer
(D) $$frac{1}{6}$$