Versatile medium access control (VMAC) protocol for mobile sensor networks

In this paper, the problem of mobility handling in wireless sensor network (WSN) is studied with a simple priority backoff technique. To incorporate this technique for stationary and mobile sensor nodes, a novel hybrid MAC protocol called VMAC is designed with a fixed frame length. VMAC combines the advantages of schedule-based MAC for energy savings and contention-based MAC for short transmission delays. To exploit the bandwidth in the network, channel reuse is encouraged and is readily integrated into the protocol. Simulation results using ns2 demonstrate that VMAC with certain frame lengths are suited for selected topologies, but the frame length of one provides sufficient performance. It is also shown that the energy consumption of VMAC is roughly one-third lower compared to pure schedule-based protocol while the average delay is about two-fold less than that of contention-based protocol in one-hop communication scenarios with frame length of one; meaning that VMAC performs very well in short-range communication. The backoff technique is also shown to be fair when nodes contend for medium access and it is even resourceful in speeding up hardware address resolution and routing.