# Soln05 - ECE 342 Communication Theory Fall 2005 Solutions...

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Unformatted text preview: ECE 342 Communication Theory Fall 2005, Solutions to Homework 5 Prof. Tiffany J Li www: http://www.eecs.lehigh.edu/ ∼ jingli/teach email: [email protected] Problem 6.1 H ( X ) =- 6 X i =1 p i log 2 p i =- (0 . 1 log 2 . 1 + 0 . 2 log 2 . 2 +0 . 3 log 2 . 3 + 0 . 05 log 2 . 05 + 0 . 15 log 2 . 15 + 0 . 2 log 2 . 2) = 2 . 4087 bits/symbol If the source symbols are equiprobable, then p i = 1 6 and H u ( X ) =- 6 X i =1 p i log 2 p i =- log 2 1 6 = log 2 6 = 2 . 5850 bits/symbol As it is observed the entropy of the source is less than that of a uniformly distributed source. Problem 6.6 The entropy of the source is H ( X ) =- 6 X i =1 p i log 2 p i = 2 . 4087 bits/symbol The sampling rate is f s = 2000 + 2 · 6000 = 14000 Hz This means that 14000 samples are taken per each second. Hence, the entropy of the source in bits per second is given by H ( X ) = 2 . 4087 × 14000 (bits/symbol) × (symbols/sec) = 33721 . 8 bits/second Problem 6.9 The marginal probabilities are given by p ( X = 0) = X k p ( X = 0 , Y = k ) = p ( X = 0 , Y = 0) + p ( X = 0 , Y = 1) = 2 3 p ( X = 1) = X k p ( X = 1 , Y = k ) = p ( X = 1 , Y = 1) = 1 3 p ( Y = 0) = X k p ( X = k, Y = 0) = p ( X = 0 , Y = 0) = 1 3 p ( Y = 1)...
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Soln05 - ECE 342 Communication Theory Fall 2005 Solutions...

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