On the Role of Early-Termination for Age of Information in Tree-Based Random Access Protocols

TL;DR

This paper analytically characterizes the average Age of Information in tree-based random access protocols, examining the impact of early termination on data freshness and reliability in IoT systems.

Contribution

It provides the first analytical model for AoI in the Capetanakis tree-based algorithm with early termination, highlighting the trade-offs between reliability and timeliness.

Findings

Early termination can improve AoI by dropping stale packets.

The model captures the dynamics of sporadic traffic and collision resolution.

Trade-offs exist between protocol reliability and data freshness.

Abstract

Age of Information (AoI) has emerged as a key metric for assessing data freshness in IoT applications, where a large number of devices report time-stamped updates to a monitor. Such systems often rely on random access protocols based on variations of ALOHA at the link layer, where collision resolution algorithms play a fundamental role to enable reliable delivery of packets. In this context, we provide the first analytical characterization of average AoI for the classical Capetanakis tree-based algorithm with gated access under exogenous traffic, capturing the protocol's dynamics, driven by sporadic packet generation and variable collision resolution times. We also explore a variant with early termination, where contention is truncated after a maximum number of slots even if not all users are resolved. The approach introduces a fundamental trade-off between reliability and timeliness, allowing stale packets to be dropped to improve freshness.