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Unformatted text preview: ECE 5670 : Digital Communications (Spring 2011) Homework 9 Due April 14 in class Instructor: Salman Avestimehr Office 325 Rhodes Hall 1. In Lecture, we discussed the various reasons why the channel gains h [ m ] vary in time (as a function of m ) and how the various dynamics operate at different time scales. All of this analysis is based on the assumption that communication occurs over a bandwidth W centered around a carrier frequency f c with f c W. (1) This assumption is not valid in ultra wideband systems (UWB) which have transmission bandwidth ranging from 3.1 GHz to 10.6 GHz (with center frequency around 6.85 GHz). Redo the analysis for this new scenario. Specifically: (a) What is the main physical mechanism that causes the channel tap gains to change at the fastest time-scale? (b) What is the fastest time-scale determined by? 2. In class we studied the performance of BPSK over Rayleigh fading channel. In par- ticular we saw that the error probability p e decays like 1 SNR . In this question we study a deeper characterization of the behavior of p e with increasing SNR...
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This note was uploaded on 10/02/2011 for the course ECE 5670 taught by Professor Scaglione during the Spring '11 term at Cornell University (Engineering School).
- Spring '11