# Prob4 - ECE 1520 Data Communications Fall 2011 Problem Set...

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Unformatted text preview: ECE 1520 Data Communications Fall 2011 Problem Set 4 Due in class, Wednesday, Oct. 26th, 2011. 1. Consider the carrier given by c ( t ) = radicalbig (2 /T ) cos (2 πf c t + φ ) , ≤ t < T . A joint ASK-PSK signal set is defined using two indices p and q : s p,q ( t ) = q radicalbig (2 E/T ) cos parenleftBig 2 πf c t + p π 4 parenrightBig , ≤ t < T, where p = 0 , 1 , . . . , 7; q = 1 , 2 Plot the signal constellation of this scheme using the low-pass equivalent. 2. (Related to Q3.10 of Proakis and Salehi (5th ed.)) A speech signal is sampled at a sampling rate of 8kHz and then quantized to 8 levels. The probabilities of the 8 levels are (The probabilities are the same as in Prob set 2.): p 1 = 0 . 25 , p 2 = 0 . 20 , p 3 = 0 . 15 , p 4 = 0 . 12 , p 5 = 0 . 10 p 6 = 0 . 08 , p 7 = 0 . 05 , p 8 = 0 . 05 Determine a binary Huffman code for this source. If the transmission uses QPSK, what is the signalling interval for his source? What would the interval have been if we did not use Huffman coding?if we did not use Huffman coding?...
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