Low-Earth Orbit (LEO) Satellite Networks (LSNs) offer a promising solution for extending connectivity to areas not covered by Terrestrial Networks (TNs). However, the rapid movement, broad coverage, and high communication latency of LEO satellites pose significant challenges to conventional handover mechanisms, resulting in unacceptable signaling overhead and handover latency. To address these issues, this paper identifies a fundamental difference between the mobility patterns in LSNs and TNs: users are typically stationary relative to the fast- moving satellites, and channel states in LSNs are often stable and predictable. This observation enables handovers to be planned in advance rather than triggered reactively. Motivated by this insight, we propose PreHO, a predictive handover mechanism tailored for LSNs that proactively determines optimal handover strategies, thereby simplifying the handover process and enhancing overall efficiency. To optimize the pre-planned handover decisions, we further formulate the handover planning problem and develop an efficient iterative algorithm based on alternating optimization and dynamic programming. Extensive evaluations driven by real-world data demonstrate that PreHO significantly outperforms traditional handover schemes in terms of signaling overhead, handover latency, and user experience.

翻译：低地球轨道（LEO）卫星网络（LSNs）为扩展地面网络（TNs）未覆盖区域的连接提供了一种前景广阔的解决方案。然而，LEO卫星的高速运动、广域覆盖及高通信延迟对传统切换机制构成了显著挑战，导致不可接受的信令开销与切换时延。为解决这些问题，本文揭示了LSNs与TNs在移动性模式上的根本差异：用户相对于高速运动的卫星通常处于静止状态，且LSNs中的信道状态往往稳定且可预测。这一观察使得切换能够被预先规划，而非被动触发。基于此洞见，我们提出了PreHO——一种专为LSNs设计的预测性切换机制，该机制主动确定最优切换策略，从而简化切换流程并提升整体效率。为优化预先规划的切换决策，我们进一步形式化了切换规划问题，并基于交替优化与动态规划开发了一种高效的迭代算法。基于真实数据的大量实验评估表明，PreHO在信令开销、切换时延和用户体验方面均显著优于传统切换方案。