Multiple Access Protocol for ad-hoc networks in VHF Data Exchange System

Very High Frequency (VHF) Data Exchange System (VDES) will provide enhanced data exchange capabilities for maritime VHF bands worldwide, supporting future e-Navigation and Global Maritime Distress and Safety System (GMDSS) modernization and protecting the current Automatic Identification System (AIS) system from heavy load. Based on the preliminary Recommendations for VDES, this paper focuses on the principle, process and algorithm implementation of Self-Organized Time Division Multiple Access (SOTDMA) channel access schemes for ad-hoc networks (ship-to-ship) in VDES, which is based on traditional TDMA and specified for marine scene. Furthermore, due to the self-organizing behavior of ad-hoc networks, slot reservation is not without potential conflicts, we thus analyze the collision probabilities of SOTDMA for two or more ships and their effects on the performance of ad-hoc networks in VDES.