SPEED-MAC: speedy and energy efficient data delivery MAC protocol for real-time sensor network applications

Although existing wakeup scheduling techniques suggest end-to-end delay guarantees for real-time applications, their fixed wakeup schedules may not meet such constraints when multiple sensors compete for the event delivery at the same time. In this paper we propose a new MAC protocol called SPEED-MAC that can provide real-time delay guarantees with much lower energy consumption for both single-source and multi-source events. The main ideas underlying the protocol are twofold. First, we introduce a novel wakeup technique called signaling wakeup, which is small only enough to detect the event occurrence. By employing the signaling wakeup we can minimize the event report latency as well as the idle listening. Second, to resolve the collisions and contentions incurred by multi-source events, the protocol employs adaptive wakeup that combines static scheduling with contention-based media access control depending on the type of traffic. The result of our analytic evaluation confirms that SPEED-MAC can provide real-time delay guarantees even for a large-scale network assuming a low event rate. We have implemented SPEED-MAC on both NS-2 and MICA2 platforms, and evaluated both the energy and the network performance of the protocol for various scenarios including multi-source, multi-sink, source-to-sink, sink-to-source, multi-cast and broadcast traffic. Our experimentation results show that SPEED-MAC can achieve an order of magnitude energy savings while providing near optimal latency compared to the existing solutions.