Joint Beamforming and Tracking for Multi-user Acoustic Communications

We address the design of a multi-user communication system over broadband acoustic channels in the context of orthogonal frequency division multiplexing (OFDM). The framework consists of multiple users transmitting to a common base station equipped with a uniform linear array. We propose a beamforming technique that exploits the spatial separation of the users, such that the base station steers a beam to each user's propagation path while placing nulls in the direction of other paths. The spatially-filtered path components of each user are recombined before data detection. Additionally, we develop an adaptive algorithm for tracking the path angles that can reduce the computational complexity of the system. The performance is demonstrated using a simulated underwater channel.