Addressing mobility in wireless sensor media access protocol

Handling mobility in wireless sensor networks presents several new challenges. Techniques developed for other mobile networks, such as mobile phone or mobile ad hoc networks are not applicable, as in these networks energy is not a very critical resource. The paper presents a new adaptive mobility-aware sensor MAC protocol (MS-MAC) for mobile sensor applications. In MS-MAC protocol, a node detects its neighbor´s mobility based on a change in received signal level from the neighbor, or a loss of connection with this neighbor after a timeout period. By propagating mobility presence information, and distance from nearest border node, each node learns its relative distance from the nearest mobile node and from nearest border node. Depending on the mobile node movement direction and the distances from mobile and border nodes, a node may trigger its neighbor search mechanism to quicken the connection setup time. Simulation results show that the new mobility-aware MAC protocol can work very energy-efficiently when the network is stationary, whereas it performs much better in terms of throughput than the existing sensor MAC (SMAC) protocol in scenarios involving mobile sensors.