A study of problem evaluation of AIS protocol with standpoint of safety of navigation and its avoidance using spacial methods

摘要

In recent years, maritime intelligent transport systems, that is ITS in an ocean, have been researched and developed. Application of radio communications and standardization for the vessels has been proceeded rapidly. In these maritime ITS, in particular, AIS broadcasts navigational data among ships, thereby can be used for safety of navigation. This system broadcast messages using self -organised TDMA so that each ship can managed slot reservation of packets autonomously. This paper investigates problems in such slot reservation procedures with traffic models of ship's location and mobility. Consequently, from the viewpoint of safe navigation, we note that there are worst cases of slot collision which has been neglected in a usual protocol of AIS. In order to avoid such worst cases, we propose modification of the protocol using the transmission power control and the signal selection based on sector antennas of standard AIS protocol. The performance improvement is evaluated by computer simulation.