Multi-user leo-satellite receiver for robust space detection of AIS messages

The coverage of the terrestrial automatic identification system (AIS) is limited to close areas off the coast. Low earth orbit (LEO) satellites can expand the service of AIS to a global range but it brings large variance in Doppler shift, path loss and propagation delay. The communication between ships and LEO satellites becomes asynchronous. The collision of AIS messages from thousands of ground cells results in loss of all collided messages. Previous papers discussed the use of a single user receiver to detect AIS messages under heavy co-channel interference but the problem was never well solved. In this paper, we present a multi-user receiver equipped with an antenna array on LEO satellites, which explores the spatial multiplexing in space detection of AIS messages and significantly improves the detection performance. The proposed receiver performs rank tracking and subspace intersection based on the signed URV decomposition ahead of blind source separation to provide robust separation of user data for single user receivers. The proposed receiver is tested in an exact dynamic AIS model.