Time Reversal Based Localization and Tracking

Abstract

• Time reversal (TR) is a fundamental physical phenomenon that takes advantage of an unavoidable but rich multipath radio propagation environment to create a spatial-temporal resonance effect, the so-called focusing effect (refer to Why Time Reversal).
• Mathematically, the TR effect is simply for the environment to serve as the computer to perform a perfect deconvolution that is, the environment behaves like a matched filter!.

• As stated, TR takes adavatage of the environment to constructively add all the radio signal components (both LoS and multipath) in a specific location at a specific timestamp (focusing effect). We design the transimitting signal as the TR version of the Forward-Echo. As a result, the transmitting signal will focus on the target and thus improving the SNR greatly. In this sense, TR works like a waveguide which navigates the transimitting power to illuminate on the target. As the focusing effect is constructed by the massive signal components, the more the multipath component is, the better the focusing effect will be.

• It is hard to quantilize the SNR improvement since it is also related to the bandwidth, multipath power profile…(TR focusing). However, when we applied TR for DOA estimations with rich multipath distortions, the TR based algorithm can achieve the same performace as the traditional ones with lower SNR up to 5dB, which implicitly indicates the superiority of TR in dealing multipath.
  

For more details. please refer to our paper (PDF）

Key words: Time Reversal, Multipath, Focusing Effect, DOA, Match Filter.