Age of Information in Two-way Updating Systems Using Wireless Power Transfer

Abstract

We consider a two-way updating system with a master node and a slave node. In each block, the master node transfers energy and updates to the slave node alternatively. The slave node performs transmission to the master node if it has sufficient energy for current block, i.e., using best-effort policy. Moreover, the slave node generates a new update immediately after the completion of previous update. We examine the freshness of the updates received by the master node in terms of \textit{age of information} (AoI), which is defined as the time elapsed after the generation of the latest received update. We derive average uplink AoI and uplink update rate as functions of downlink update rate in closed form. The obtained results illustrate the performance limit of the unilaterally powered two-way updating system in terms of timeliness and efficiency. The results also specify the achievable tradeoff between the update rates of the two-way updating system.