Separation of AIS Transponder Signals (AIS)

Themes: Signal processing for communication

AIS is a VHF communication system for ship transponders. Seen from a satellite, transponder messages overlap. The aim is to separate these using an antenna array.
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.

Received and decoded AIS locations plotted on a map

Project data

Researchers: Alle-Jan van der Veen, Mu Zhou
Starting date: October 2010
Closing date: May 2014
Contact: Alle-Jan van der Veen

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