Achieving the Age-Energy Tradeoff with a Finite-Battery Energy Harvesting Source

TL;DR

This paper investigates how to optimally manage energy and update timing in energy-harvesting systems with finite batteries to minimize information age, extending previous results to larger battery capacities.

Contribution

It generalizes the threshold-based optimal policy structure for any integer battery capacity, providing tools to derive optimal policies for arbitrary battery sizes.

Findings

Optimal policies have a threshold structure for any battery size.

Minimum average AoI equals the threshold at the highest energy state.

Explicit characterization of the threshold structure for finite batteries.

Abstract

We study the problem of minimizing the time-average expected Age of Information for status updates sent by an energy-harvesting source with a finite-capacity battery. In prior literature, optimal policies were observed to have a threshold structure under Poisson energy arrivals, for the special case of a unit-capacity battery. In this paper, we generalize this result to any (integer) battery capacity, and explicitly characterize the threshold structure. We obtain tools to derive the optimal policy for arbitrary energy buffer (i.e. battery) size. One of these results is the unexpected equivalence of the minimum average AoI and the optimal threshold for the highest energy state.