Designing and improving the access to the channel in the automatic ships identification system based on satelite

Automatic Identification System (AIS) is a marine equipment that provides monitoring of vessels using satellite. AIS system uses satellites as a platform to send and receive information. Ships send their AIS signals to satellites, and the satellites receive these signals and transmit them to associated ground bases. Ground bases then process and analyze the received information to determine the position, speed, direction and other information about the ships. When sending messages by vessels, the vessels may choose the same time slot, which causes collisions in the channel. To prevent collision, AIS system uses SOTDMA algorithm. One of the problems of this algorithm is the problem of high delay in the AIS system compared to the selection interval and the number of sent packets. To overcome this problem, three solutions are proposed: reducing the distance between central gaps in SI, reducing the distance between NIs, and reducing the candidate selection distance. In this article, the method of reducing the distance between the central gaps is used. Also, another feature mentioned in this article is reducing the error rate depending on the reference algorithm. The simulation results of the proposed algorithm show its proper performance in reducing the delay of about 19 seconds of sent packets.