Distributed Adaptive Time Slot Allocation for WiMAX Based Maritime Wireless Mesh Networks

We envisage extending radio coverage of the existing terrestrial wireless broadband networks to the sea to provide ships with cost-efficient high-speed connection to the Internet. This is achieved by forming a WiMAX based maritime wireless mesh network where ships are network nodes connected to the land station across multiple hops. In such a maritime wireless mesh network, time slot allocation is an important issue as it affects the performance in terms of throughout and delay. This papers proposes a distributed adaptive time slot allocation (DATSA) scheme for WiMAX mesh MAC protocol. DATSA is a distributed scheme that allocates time slots robustly by taking into consideration difference between radio reception range and interference range, and latency in scheduling control messages. DATSA has a method to monitor reception quality of an allocated time slot, in order to detect the effect of topology changes due to ship mobility, etc. Based on the monitoring outcome, the method adaptively changes the time slot allocation if necessary. We have evaluated DATSA through random event simulation using QualNet. The simulation results confirm that DATSA outperforms the original WiMAX mesh MAC protocol that has no adaptive time slot allocation, in terms of throughput, average packet delay, and packet delivery ratio.