AstroTimer: Rethinking Non-Access Stratum Timers in LEO Constellations

TL;DR

AstroTimer offers an adaptive, low-cost timer framework tailored for LEO satellite networks, significantly improving registration efficiency and reducing signaling overloads in non-terrestrial 5G/6G systems.

Contribution

It introduces a novel, closed-form timer model specifically designed for LEO constellations, addressing limitations of existing 3GPP timers in dynamic satellite environments.

Findings

Reduces registration time and retry frequency

Decreases user equipment energy consumption

Prevents signaling overloads

Abstract

Low-Earth Orbit (LEO) constellations expand 5G coverage to remote regions but differ fundamentally from terrestrial networks due to rapidly changing topologies, fluctuating delays, and constrained onboard resources. Existing 3GPP Non-Access Stratum (NAS) timers, inherited from terrestrial and geostationary (GEO) or medium Earth orbit (MEO) systems, fail to accommodate these dynamics, leading to signaling storms and inefficiency. This paper introduces AstroTimer, a lightweight, adaptive framework for sizing NAS timers based on LEO-specific parameters such as link variability, processing delays, and network-function placement. AstroTimer derives a closed-form timer model with low computational cost and optimizes both watchdog and backoff timers for the 5G registration procedure. Simulation results demonstrate that AstroTimer significantly reduces registration time, retry frequency, and user equipment (UE) energy consumption compared to 3GPP defaults, while preventing signaling overloads. The proposed approach provides an operator-ready foundation for reliable, efficient, and scalable non-terrestrial 5G/6G deployments.