Multiple Input and Multiple Output Configuration for Full-duplex Cognitive Underwater Acoustic Communications: Benefits and Costs

As a new one of underwater wireless data exchange families, full-duplex cognitive underwater acoustic communications (FDCUACs) play an important role not only for improving the performance of the underwater acoustic communications, but also for protecting the normal communications among the halobios simultaneously, which has been attracted widely attention and deeply research. Since the configuration on multiple input and multiple output (MIMO) is employed in the FDCUACs, it has the potential to improve the performance such as channel capacity, interference cancellation based on beamforming, and spectrum sensing according to transmitted direction significantly. However, there are some costs such as how to overcome the co-channel interference, how to synchronize all channels, and how to provide simple detection. In order to stimulate new research, this paper first reviews the benefits, then discusses the costs, and presents a benefit-cost analysis for the MIMO configuration deployed in the FDCUACs. Based on the above overview, the paper is also concluded by outlining a range of future research topics that may find their way into the FDCUAC or next-generation underwater wireless systems.