Optimal Resource Allocation for Wireless Powered Sensors: A Perspective from Age of Information

We investigate a wireless powered sensor network, in which multiple sensors generate data and send their data to a base station (BS) periodically. Each sensor first harvests energy from the BS via wireless power transfer and then uses its available energy to transmit to the BS its data. We target minimal average age of information, by optimizing the energy harvesting time and the bandwidth allocation during the sensors' transmissions. The research problem is hard to solve, as some notations in the problem do not have a closed-form expression. To optimally solve the problem, we first show that there is a one-to-one mapping from the energy harvesting time to the bandwidth allocation. We also develop a method to obtain the bandwidth allocation vector corresponding to each value of the energy harvesting time. Then we get the optimal energy harvesting time by investigating and comparing different sub-regions of energy harvesting time. Numerical results show optimality of our solution and its performance gain over a benchmark scheme based on the traditional threshold-based method.