Abstract
It has been shown that time-reversal (TR) techniques focus energy back to the dominant scatters, lead to super-resolution focusing, and gains in detection. Time reversal has so far mainly been studied when the channel remains invariant between the initial and time-reversed signal transmission times. In this letter, we relax this assumption and study the benefits of TR over time-varying channels. To do so, we compare a time-reversed and a non time-reversed system by comparing the mutual information between the channel impulse response and channel outputs given the transmitted signals. We present analytical results for a simple scalar problem which illustrates the impact of nonstationary channels on TR, and for general channels, numerically evaluate the difference in mutual informations, which demonstrate that, if the channels are nonstationary yet correlated, TR may still provide mutual information gains over non time-reversed systems.
Highlights
I N this letter, we analyze radar-based time reversal (TR) over time-varying channels using mutual information as comparison metric
Most of these important contributions in TR were derived assuming the channel to be invariant from the initial signal transmission to the time-reversed re-transmission [1]–[6]
We introduce the relevant mutual information quantity for these models in Section III, before analytically comparing the difference in mutual information for TR and conventional channels in Section IV, where we analytically work out an intuitive special scalar case which illustrates the effect of channel correlation between the two stages on the mutual information
Summary
I N this letter, we analyze radar-based time reversal (TR) over time-varying channels using mutual information as comparison metric. TR may lead to super-resolution spatio-temporal focusing using multiple antennas, and detection gains for single and multiple antennas [1]–[6] Most of these important contributions in TR were derived assuming the channel to be invariant from the initial signal transmission to the time-reversed re-transmission [1]–[6]. We make analytical progress by introducing and analyzing the mutual information in TR systems as compared to conventional systems for time-varying channels. A single antenna transceiver first probes the channel It subsequently transmits the time-reversed signal it received from the initial probe. Our central contributions are 1) analyzing TR using information theoretic metrics for the first time, and 2) using this framework to quantitatively analyze the impact of time-varying channels on TR as compared to conventional systems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
