Separation of AIS Transponder Signals (AIS)

Themes: Signal processing for communication

Ships use the AIS transponder system to transmit their own location/speed/bearing and receive locations from neighboring ships, for safety purposes. Basestations in harbors track the ships as well, and the results are available in public databases.

From a tower or a satellite, many more messages are seen and often these messages (partially) overlap, currently resulting in fatal interference and causing delays in the tracking the location. In this project, we aim to use source separation algorithms to separate the messages and individually decode them. The algorithms are based on blind beamforming techniques such as the constant modulus algorithm and subspace intersection algorithms. Existing algorithms are not directly suitable due to the partial overlap and short data blocks.

To test the algorithms, we built a 3-antenna receiver system for receiving and separating transponder messages. Online tracking of ships as seen from the EWI building, 17th floor, looking South-West.