# Age of Information With Prioritized Streams: When to Buffer Preempted Packets?

## TL;DR

This paper analyzes the Age of Information in prioritized streams sharing a service, revealing that discarding preempted packets can sometimes improve AoI, with theoretical and numerical insights into when to buffer or discard.

## Contribution

It introduces a stochastic hybrid systems model for AoI with prioritized streams and compares buffering versus discarding preempted packets, identifying conditions favoring each approach.

## Key findings

- Buffering preempted packets can sometimes worsen AoI.
- Discarding preempted packets may be optimal in certain scenarios.
- Numerical results confirm the theoretical trade-offs.

## Abstract

In this paper, we consider N information streams sharing a common service facility. The streams are supposed to have different priorities based on their sensitivity. A higher priority stream will always preempt the service of a lower priority packet. By leveraging the notion of Stochastic Hybrid Systems (SHS), we investigate the Age of Information (AoI) in the case where each stream has its own waiting room; when preempted by a higher priority stream, the packet is stored in the waiting room for future resume. Interestingly, it will be shown that a "no waiting room" scenario, and consequently discarding preempted packets, is better in terms of average AoI in some cases. The exact cases where this happen are discussed and numerical results that corroborate the theoretical findings and highlight this trade-off are provided.