Underwater MIMO Communications by RF Signals: Capacity Analysis, Simulations, and Experiment

摘要

This paper gives an analysis on channel capacity of MIMO communications in seawater, in which zero-forcing (ZF) is introduced in order to mitigate interference among transmitted data streams. It is shown that, by setting the antenna spacing of both the transmit and receive sides to more than 0.33 of the wavelength determined by electrical characteristics of seawater, MIMO communications brings channel capacity close to upperbound. Also, it is derived that the MIMO communications is robust on the variance of the electrical conductivity of seawater through evaluation on the channel capacity. Experiment on 2 × 2 MIMO communications has been conducted in the shallow water. The results of the experiment show that MIMO transmission with bitrate of 1 Mbps at payload has been demonstrated with 64 QAM communications in carrier frequency of 1 MHz in distance of 1.0m when the transmit power per antenna is +34 dBm.