On the use of channel state for energy efficient information retrieval in sensor networks

We consider distributed information retrieval for sensor networks with cluster heads or mobile access points. The performance metric used in the design is energy efficiency defined as the ratio of the average number of bits reliably retrieved by the access point and the total amount of energy consumed. We demonstrate that opportunistic strategies that use channel state information may not be optimal when channel acquisition at individual sensors consumes substantial energy. We then propose a distributed opportunistic transmission protocol using a combination of carrier sensing and backoff strategy that incorporates channel state information of individual sensors. By selecting a set of sensors with the best channel states to transmit, the proposed protocol achieves the upper bound on energy efficiency when the signal propagation delay is negligible. This protocol provides a distributed solution to the general problem of finding maximum/minimum. It can also be extended to solve the problem of network lifetime maximization.