A Novel Feedback-based MAC Protocol Design for Cognitive VDES towards E-navigation

VHF Data Exchange System (VDES) has tremendous potential in developing the E-navigation strategy and guaranteeing navigation safety. Different from the traditional Automatic Identification System (AIS), VDES enables various maritime applications by incorporating the functions of Application Specific Messages (ASM) and VHF Digital Exchange (VDE). Due to determining the access method, the media access control (MAC) protocol plays a critical role in VDES for vessels. However, the only Slot-Aloha protocol recommended by ITU-R 2092-1 results in a relatively low channel utilization rate that cannot meet the communication demands. Therefore, in this paper, we propose a feedback-based with an improved Hexslot structure (FIH) MAC protocol by employing the tools of cognitive radio to improve the channel utilization ratio. By reallocating the functions of the Hexslot structure, the FIH-MAC protocol reserves a feedback bit in the primary user’s date packet to inform the occupancy status of the time slot in the next frame. Other vessels dynamically select the optimal time slot to access the channel according to the information in the feedback bit. Simulation results show that our proposed MAC protocol outperforms the traditional Slot-Aloha protocol in terms of transmission collisions and channel utilization rate. The proposed FIH-MAC protocol can support the development of VDES and the E-navigation strategy.