49 / 2019-12-10 02:00:00

Spatial diversity of underwater acoustic channels and its application for robust communications

underwater acoustic communication; spatial diversity; time reversal; decision feedback equalizer

IEEE SAM 2020: Special Sessions > Multi-Sensor Data Fusion for Underwater Application

Underwater acoustic (UWA) channel is regarded as one of the most difficult wireless channels. It is characterized by large multipath spread which can easily reach tens of milliseconds or even hundreds of milliseconds, resulting in severe inter symbol interference (ISI). However, the performance of UWA communication, especially coherent UWA communication greatly depends on how well the receiver can suppress the ISI. In UWA waveguides, the channels from the source to receivers at different depths can be very different (i.e. non-coherent) when the receivers are separated in vertical by several wavelengths (i.e. >4) corresponding to the signal frequency. Therefore, a vertical array with multiple receivers is often used in order to realize robust UWA communications which makes full use of the spatial diversity of UWA channels. This paper will briefly introduce the spatial diversity of UWA channels using experimental data and review two commonly used channel equalizers, passive time reversal cascaded with single channel decision feedback equalizer (PTR-DFE) and multichannel DFE (M-DFE). The performance of these two equalizers is also compared using experimental data. This paper also introduces the recent advances of these two equalizers, for example mobile UWA communication, sparse direct adaptive equalization, and robust UWA communication under impulsive noise.