Capacity analysis of underwater acoustic MIMO communications

First introduced in the field of radio communications, Multi-Input Multi-Output (MIMO) principle consists of transmitting digital data from N
_t
transmitters to N
_r
receivers within the same frequency band. During the last decade, theoretical works and real-life experiments in wireless local area and cellular networks have demonstrated and confirmed that MIMO was a breakthrough in digital communications. Recently, MIMO principle has been applied to underwater acoustic communications (UAC) with promising results. However, only few work have been already done on the expected gain of MIMO over underwater channel. Main objective of our paper is on the one hand to quantify theoretically the MIMO gain in underwater acoustic channel by using Shannon capacity analysis and on the other hand to give guidelines to optimize MIMO underwater system with respect to capacity maximization.