2.2 Wireless Sensor Network Operating Systems............................ 4

Wireless sensor “motes”—small embedded systems equipped with radios for wireless communication—are almost always expected to operate unattended for long periods of time, relying upon batteries as a power source. As the vast majority of energy consumed by motes can be attributed to radio usage, the development of medium access control (MAC) protocols which seek to minimize energy consumption is an important area of wireless sensor network research. Recent MAC protocols reduce energy usage by placing the radio in a low-power sleep state when not sending or receiving transmissions. This project investigates energy usage in three such protocols—AS-MAC, SCP-MAC, and Crankshaft–on physical sensor hardware. It additionally presents BAS-MAC, an energy-efficient protocol of our own design. We evaluate our implementation of these four protocols on TelosB motes over multiple sensor network topologies. Our evaluations show that in single-hop networks with large send intervals and staggered sending, AS-MAC is best in the local gossip and convergecast scenarios, while SCP-MAC is best overall in the broadcast scenario. We conjecture that Crankshaft would perform best in extremely dense hybrid (unicast and broadcast) network topologies, especially those which broadcast frequently. Finally, BAS-MAC would be optimal in networks which utilize hybrid traffic with infrequent broadcasts, and where broadcasting is performed by motes that do not have an unlimited power source.