Distributed opportunistic transmission for wireless sensor networks

We consider protocol design for extracting information from sensors by a mobile access point. Energy efficiency, defined as the expected number of bits reliably received for each unit of energy consumed, is used as the performance measure. A distributed opportunistic information retrieval protocol which exploits channel state information (CSI) is proposed. Referred to as the CSI-based carrier sensing, this protocol encodes the channel state into the backoff strategy of carrier sensing. When the propagation delay is negligible, CSI-based carrier sensing achieves the highest energy efficiency of the opportunistic strategy. For significant propagation, we construct the backoff function which maps the channel state to backoff time to minimize the performance loss. The CSI-based carrier sensing with the constructed backoff strategy is shown to be robust to propagation delay.