Low power TDMA in large wireless sensor networks

In this paper we present a novel TDMA scheme for a large population of sensors interconnected by a wireless multihop network. Applications of this wireless sensor network include battlefield surveillance, space exploration and condition based monitoring. Key characteristics of this system are the large number of sensor nodes and the need to rely on battery operation for a long period of time. Since communication is a major consumer of energy, low power communication protocols play a critical role in wireless sensor networks and have significant impact on the overall energy dissipation of these networked systems. This paper focuses on an energy efficient TDMA protocol, power aware clustered TDMA (PACT), that adapts the duly cycle to the user traffic. In other words, the radio is powered off if the network is inactive. Moreover, we apply passive clustering to take advantage of the redundant dense topology and prolong the lifetime of the entire network even further. At a given time, only a subset of network nodes (i.e., cluster heads and gateways) participates in the communication. The role of cluster heads and gateways is rotated according to their energy levels. The clustering requires no explicit control messages and therefore incurs negligible energy overhead. Using the proposed protocol, simulation and analytical results show significant improvement in energy saving and network lifetime.