Joint time reversal precoding and spatial diversity technique for acoustic communication in shallow water environment

Intersymbol interference (ISI) is one of the main issues in underwater acoustic communication (UAC) link development. Meanwhile, Time Reversal (TR) precoding is a promising method to mitigate ISI by means of its inherent property of spatial-temporal focusing. For the ISI problem solution and a reliable UAC link achievement, the authors propose the combination of TR precoding and maximum ratio combining (TR-MRC) techniques applied to a single-input-multi-output-OFDM (SIMO-OFDM) scheme. The system performance is observed based on Monte Carlo simulations and the analytical expressions in terms of bit-error-rate (BER) are presented to support the simulation results. There are three schemes compared, i.e.: proposed method (TR-MRC), TR-equally gain combining (TR-EGC) and simple TR. The three schemes are compared in three conditions of water depth. The analytical performance and simulation results show that the proposed method has the best performance between the other two schemes in three water depths of the towing tank. By using 2 hydrophones as a receiver array, the proposed method is proven to be superior to the simple TR. The superior performance produced up to 6 dB compared to the TR-EGC scheme and 8 dB over simple TR when the BER value is 0.1.