Channel characterization of time reversal UWB communication systems
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An ultra wideband (UWB) communications system that applies time reversal to transmit the desired signal is investigated. Exact expressions for the first- and second-order moments, cross-correlation, intersymbol interference metric, and correlation coefficient of time reversal (TR) UWB equivalent channel are derived in terms of the physical channel parameters such as delay spread and mean excess delay. These expressions are verified by simulated and experimental results. It is shown that TR-UWB excess delay is very smaller than UWB and its delay spread decreases as signaling bandwidth increases. Semi-analytical results show that the time reversal UWB delay spread is approximately the same as UWB. Furthermore, an ISI metric is derived for TR-UWB channel based on transmitted signal and UWB channel parameters. Moreover, correlation coefficient of two TR-UWB received signals with different power delay profile is computed analytically. Simulation and analytical results show that for τ > 0.3T w correlation coefficient is below 0.25 and for τ > T w correlation coefficient is zero, where T w is the transmitted pulse width. Finally, theoretical performance of a receiver with one tap matched filter is computed and compared with measured and simulated result.
KeywordsTime reversal Correlation coefficient Autocorrelation ISI UWB Delay spread
The authors would like to thank ITRC (Iran telecommunication Research Center) for their invaluable assistance and funding for this research.
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