In this paper, we proposed the RF-MAC protocol that specifically
addresses the problems of the joint selection of energy
transmitters and their frequencies based on the collective impact
on charging time and energy interference, setting the maximum
energy charging threshold, requesting and granting energy,
and energy-aware access priority. The grouping of the ETs
into two sets with varying transmission frequencies, and the
minimal control overhead are both geared to keep the hardware
requirements simple, and the protocol easier to implement. Our
protocol delves on the important issue of how to determine
the energy vs. data communication tradeoff, especially as one
occurs as the cost of the other.