基于用户分群的低轨卫星系统切换管理策略

低轨（LEO）卫星系统具有通信距离远、覆盖范围广等诸多优势，在应急通信、灾害预警等领域发挥着重要作用，尤其能有效弥补地面基站无法服务偏远山区、海洋等盲区的缺陷。然而，LEO卫星高速移动会导致用户终端频繁切换，同时在用户聚集场景下，用户群组并发切换将导致LEO卫星系统发生网络拥塞问题。为此，提出一种基于用户分群的多波束LEO卫星系统切换管理策略。建立多波束覆盖模型，基于该模型设计群组切换管理机制，在成员选择的过程中考虑切换触发时刻和最佳波束小区2个因素，将具有相似切换行为的用户分为一组，以此降低系统的信令开销。在此基础上，从分群处理、群组切换、资源释放3个方面设计完整的切换流程以及切换信令交互机制，并基于OPNET软件搭建LEO卫星系统仿真平台。测试结果表明，该策略能够简化切换管理过程中的重复操作，降低系统信令开销和平均切换时延，提高切换成功率，且用户聚集数目越多，其性能相对传统用户独立切换方案的提升效果越明显。

Handover Management Strategy Based on User Grouping for LEO Satellite System

Low Earth Orbit(LEO)satellite system has many advantages such as long communication distance and wide coverage. It plays an important role in emergency communication,disaster early warning and other fields. In particular,it can effectively make up for the defect that the ground base station can not serve the blind areas such as remote mountainous areas and oceans. However,the high-speed movement of LEO satellite will lead to frequent switching of user terminals. At the same time,in the scenario of user aggregation,concurrent handover of user groups will lead to network congestion in LEO satellite system.Therefore,a handover management strategy of multi-beam LEO satellite system based on user grouping is proposed.A multi-beam coverage model is established,and the group handover management mechanism is designed based on this model.In the member selection process,the two factors considered are handover trigger time and optimal beam cell.Users with similar handover behavior are assembled into a group,to reduce the signaling overhead of the system. On this basis,a complete handover process and handover signaling interaction mechanism are designed considering three aspects:cluster processing,group handover,and resource release. The LEO satellite system simulation platform is built based on OPNET software. The test results show that this strategy can simplify the repeated operation in the handover management process,reduce the system signaling overhead and average handover delay,and improve the handover success rate. The more the number of users,the more obvious the improvement effect of the performance is compared with the traditional user independent handover scheme.