Superimposed training passive time reversal for low SNR communications

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Ref.: IEEE Access, Vol.14, pp.92100, July 2026

Abstract:
This paper presents a superimposed training passive time-reversal (STpTR) approach to deal with the passive time-reversal (pTR) environmental mismatch between the probe and the message transmissions. The probe is superimposed on the message and therefore, the probe and the message use the same sound channel. The proposed method uses a real-time Doppler-corrected probe to estimate the channel and perform pTR. The method compares 3 alternative strategies: the temporal diversity provided by repetitions of the same signal, the spatial diversity provided by two different geometry arrays of 4 hydrophones, and a combination of both with 8 hydrophones. STpTR mitigates multipath and performs error correction through coherent averaging. Residual intersymbol interference is removed by a Wiener filter. Results from a low signal-to-noise ratio (SNR) shallow-water experiment indicate the suitability of STpTR for both single and multichannel combining. STpTR combined with a Wiener filter provided an average mean-square error gain of up to 2.92 dB for single channels and 4.17 dB for multichannel combining, compared to a Wiener filter alone. The proposed method achieved a BER< 10−2, for an in-band input SNR as low as −8 dB.

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