A polling MAC with reliable RF recharging of sensor nodes

We describe a wireless sensor network with a medium access control (MAC) protocol that supports wireless recharging of nodes. The MAC protocol uses round-robin scheduling with 1-limited service for simplicity. Nodes that are running out of energy may request a recharge through a radio-frequency pulse. To reduce the likelihood of energy outage, we propose a collaborative protocol in which nodes that hear another node´s recharge request will repeat it until the master node responds with a recharge pulse. Performance of the proposed protocol is evaluated using a probabilistic energy expenditure model. Our results indicate that the collaborative protocol can ensure uninterrupted network operation under a widely varying range of parameter values.