# Scheduling Status Updates to Minimize Age of Information with an Energy Harvesting Sensor

## TL;DR

This paper investigates optimal scheduling policies for energy-harvesting sensors to minimize the age of information, considering energy constraints and channel unreliability, and derives bounds on the average age.

## Contribution

It formulates an age-optimal threshold policy considering energy state and current age, and analyzes average age under various energy arrival scenarios.

## Key findings

- Existence of a positive age threshold for transmission at any finite energy arrival rate.
- Derived a lower bound on average age for general battery sizes.
- Identified that transmission occurs at a rate lower than energy arrival rate under optimal policies.

## Abstract

Age of Information is a measure of the freshness of status updates in monitoring applications and update-based systems. We study a real-time remote sensing scenario with a sensor which is restricted by time-varying energy constraints and battery limitations. The sensor sends updates over a packet erasure channel with no feedback. The problem of finding an age-optimal threshold policy, with the transmission threshold being a function of the energy state and the estimated current age, is formulated. The average age is analyzed for the unit battery scenario under a memoryless energy arrival process. Somewhat surprisingly, for any finite arrival rate of energy, there is a positive age threshold for transmission, which corresponding to transmitting at a rate lower than that dictated by the rate of energy arrivals. A lower bound on the average age is obtained for general battery size.