Medium access control with mobility-adaptive mechanisms for wireless sensor networks

Mobility in wireless sensor networks poses unique challenges to the Medium Access Control (MAC) protocol design. Previous MAC protocols for sensor networks assume static sensor nodes and focus on energy-efficiency. In this paper, we present MMAC, a mobility-adaptive, collision-free MAC protocol for mobile sensor networks. MMAC caters for both weak mobility (e.g. topology changes, node joins and node failures) and strong mobility (e.g. concurrent node joins and failures, and physical mobility of nodes). When using MMAC, nodes are allowed to transmit at particular time-slots, based on the traffic information and mobility pattern of the nodes. Allowing transmission at particular time-slots makes MMAC a schedulingbased protocol, thereby guaranteeing collision avoidance. Simulation results indicate that the performance of MMAC is equivalent to that of TRAMA in static sensor network environments. In sensor networks with mobile nodes or high network dynamics, MMAC outperforms existing MAC protocols, including TRAMA and S-MAC, in terms of energy-efficiency, delay and packet delivery.