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.

翻译：低地球轨道（LEO）星座将5G覆盖扩展至偏远地区，但由于拓扑结构快速变化、延迟波动以及星载资源受限，其与地面网络存在根本性差异。现有的3GPP非接入层（NAS）定时器继承自地面及地球静止轨道（GEO）或中地球轨道（MEO）系统，无法适应这些动态特性，导致信令风暴和效率低下。本文提出AstroTimer，一种基于LEO特有参数（如链路可变性、处理延迟和网络功能部署）进行NAS定时器设置的轻量级自适应框架。AstroTimer以较低计算成本推导出闭式定时器模型，并针对5G注册流程同时优化看门狗定时器和退避定时器。仿真结果表明，与3GPP默认设置相比，AstroTimer显著降低了注册时间、重试频率和用户设备（UE）能耗，同时防止了信令过载。所提出的方法为可靠、高效且可扩展的非地面5G/6G部署提供了可供运营商直接应用的基础。