Beamforming and DOA Estimation Enabled by Active IRS in Maritime Environments

This paper investigates a system design that leverages active intelligent reflecting surfaces (AIRS) to enable dynamic beamforming and enhance the direction of arrival (DOA) estimation at airborne base stations (BS) in complex sea-surface multipath environments. By deploying active IRS on the sea surface, signals from maritime targets are amplified and continuously reflected to the airborne BS. This approach not only significantly improves signal transmission rates but also effectively mitigates the adverse impact of sea-surface multipath reflections on long-range airborne DOA estimation. Using prior information comprising coarse DOA estimates of maritime targets and realtime BS coordinates, we optimize the IRS phase-shift matrix to achieve its single-beam-forming requirement through a genetic algorithm. By controlling the scanning of the IRS reception mainlobe within the prior estimation region, high-precision DOA estimation is realized. The simulation results demonstrate that the proposed scheme significantly improves the performance of the DOA estimation.