Wireless MAC layer flexibility for extending effective system lifetime

Abstract

The scenario of wireless devices deployed in an ad hoc network is a compelling one. For the system to support its assigned tasks, nodes must cooperate to forward data packets through the network. The act of forwarding, however, is directly linked to node lifetime. The more a node forwards data packets, the sooner it depletes its battery through use of its high energy-consuming radio. Once forwarding nodes deplete their batteries, the network may partition and fail to provide its designated services. To reduce the burden on nodes maintaining network connectivity, we propose to balance energy consumption among all participating networked nodes, so they all fail at approximately the same time. We do this through our Medium Access Control (MAC) layer protocol, SEESAW, which offloads communication control overhead from heavily loaded nodes to more lightly loaded neighbors. SEESAW'S unique combination of asynchrony, asymmetry and batching allow probabilistic communication with reliable delivery, while both reducing and balancing energy consumption. We present SEESAW and an accompanying online, distributed, self-tuning algorithm. We evaluate SEESAW through simulation using our detailed energy modeling simulator, SENSIM, and implementation on Mica2 Motes in TinyOS. Our results show SEESAW is competitive in terms of energy consumption and delivery performance with related protocols, despite additional overhead needed for an asynchronous and asymmetric protocol. Additionally, we show SEESAW successfully balances consumption among networked nodes while providing acceptable delivery performance with static random topologies and static, random, and bursty application workloads.