On the characterization of AIS traffic at the satellite

Satellite-aided Automatic Identification System (AIS) has drawn the attention from the maritime community for worldwide vessel tracking and monitoring. The satellite reception of AIS packets is viable, although the standard has been designed for inter-vessel communication and vessel collision avoidance. A model and an extensive analysis of the Medium Access (MAC) protocol performance of AIS can on the one hand shed light on possible protocol improvements and on the other hand help satellite operators to design satellite-aided AIS reception systems. The objective of the paper is to analytically model the AIS Self-Organized Time Division Multiple Access (SOTDMA) traffic pattern at the satellite and to investigate the realistic behavior of SOTDMA via simulations. In the paper we demonstrate that SOTDMA can be seen as a slotted random access protocol at the satellite which noteworthy simplifies the analysis of the protocol performance. Exploiting this connection, an optimization on the frequency of AIS packets generation is derived here, which maximizes the vessel tracking frequency.