OFDM demodulation using virtual time reversal processing in underwater acoustic communication

TL;DR

This paper introduces a virtual time reversal processing method for OFDM in underwater acoustic communication, reducing interference and improving performance over traditional passive time reversal processing through channel convolution with estimated channel response.

Contribution

The paper proposes a novel VTRP method that replaces probe signal convolution with channel response convolution, enhancing underwater OFDM communication performance.

Findings

VTRP outperforms PTRP in simulations and experiments.

VTRP effectively reduces ISI in underwater channels.

Sparse channel estimation methods improve VTRP accuracy.

Abstract

The extremely long underwater channel delay spread causes severe inter-symbol interference (ISI) for underwater acoustic communications. Passive time reversal processing (PTRP) can effectively reduce the channel time dispersion in a simple way via convolving the received packet with a time reversed probe signal. However the probe signal itself may introduce extra noise and interference (self-correlation of the probe signal). In this paper, we propose a virtual time reversal processing (VTRP) for single input single output (SISO) Orthogonal Frequency Division Multiplexing (OFDM) systems. It convolves the received packet with the reversed estimated channel, instead of the probe signal to reduce the interference. Two sparse channel estimation methods, matching pursuit (MP), and basis pursuit de-noising (BPDN), are adopted to estimate the channel impulse response (CIR). We compare the performance of VTRP with the PTRP and without any time reversal processing through MATLAB simulations and the pool experiments. The results reveal that VTRP has outstanding performance over time-invariant channels.