Performance evaluation of Multi-User MIMO Underwater Acoustic Communications

This paper presents a study of Multiuser Multiple Input Multiple Output (MU-MIMO) as a multi-access method for underwater acoustic communications. Traditional multi-access schemes such as Time Division Multiple Access (TDMA) suffer from limited data rates due to an inefficient sharing of communication resources. In a MU-MIMO systems, each user can be viewed by the receiver as an input of a conventional MIMO channel. The receiver can then exploit the spatial diversity to decode the input streams of each users. Achievable rates of MU-MIMO with Successive Interference Cancellation (SIC) are studied in a first place, and compared with single user and TDMA theoretical performance. The theoretical rates are computed on channels sounded at-sea for a two-user configuration so as to evaluate what gains can be expected from the MU-MIMO approach. Finally, comparisons with the effective rates obtained from simulations of full modulation and demodulation stages using measured channels and the underWater AcousTic channEl Replay benchMARK (WATERMARK) are provided.