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GATE EC : Communications Champion Quiz 3
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Question 1
A source alphabet consists of N symbols with the probability of the first two symbols being the same. A source encoder increases the probability of the first symbol by a small amount ε and decreases that of the second by ε. After encoding, the entropy of the source
Question 2
A fair coin is tossed repeatedly until a ‘Head’ appears for the first time. Let L be the number of tosses to get this first ‘Head’. The entropy H(L) in bits is ________.
Question 3
The capacity of a Binary Symmetric Channel (BSC) with cross-over probability 0.5 is ________
Question 4
Weak components of a signal with non-flat psd can be protected against channel noise and frequency dependent channel response by a pair of spectral operations. These components can be amplified before transmission and attenuated after reception leading to both flat end-to-end channel response and higher SNR. What are the names of these operations
Question 5
What would be the bandwidth of the output signal of SSB-AM (USB) modulator illustrated below when the bandwidth of the baseband message signal is 3 kHz and c(t) = 2sin(200 * 103 πt).
Question 6
A memory less source limits n symbols each with a probability p. The entropy of the source as a function of n
Question 7
A zero memory source emits six messages with probabilities 0.3, 0.25, 0.15, 0.12, 0.1and 0.08. If binary Huffman coding is used, what will be the average code length?
Question 8
A communication channel with AWGN operating at a signal to noise ratio SNR>>1 and bandwidth B has capacity C1. If the SNR is doubled keeping B constant, the resulting capacity C2 is given by
Question 9
A source generates three symbols with probabilities 0.25, 0.25, 0.50 at a rate of 3000 symbols per second. Assuming independent generation of symbols, the most efficient source encoder would have average bit rate as
Question 10
The AM signal gets added to a noise with Power Spectral Density Sn(f) given in the figure below. The ratio of average sideband power to mean noise power would be:
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Jun 7ESE & GATE EC
