Related Work

Handover schemes in LEO satellite systems. The inherent mobility in LEO satellites results in limited connection time between the GS and satellite. To hold the constant communication between them, handover schemes in LEO satellite systems, including the selection of the first satellite and the next satellite, have been widely studied. Authors in [14], [40], [41], [49] propose to select the satellite with the longest remaining service time which can reduce the change frequency between the GS and satellites. Prior efforts in [14], [32], [40], [41] propose to select the satellite with the closest distance to guarantee the link quality as high as possible. Works in [31], [33] propose to select the satellite with the least traffic load which can achieve the load balance on the satellites as much as possible, thus reducing the occurrence of network congestion. However, these studies only focus on the performance of one hop between the GS and satellite, such as handover times, blocking probability, forced termination probability, link using different satellite-ground interconnection algorithms. failure probability, etc., without considering the impact on the entire network.

低轨（LEO）卫星系统中的切换方案。LEO卫星固有的移动性导致了地面站（GS）与卫星之间的连接时间有限。为了维持它们之间的持续通信，LEO卫星系统中的切换方案，包括初始卫星和下一个卫星的选择，已被广泛研究。文献[14], [40], [41], [49]的作者提出选择剩余服务时间最长的卫星，这可以降低GS与卫星之间的切换频率。先前在[14], [32], [40], [41]中的工作提出选择距离最近的卫星，以尽可能保证链路质量。文献[31], [33]的工作则提出选择业务负载最轻的卫星，以尽可能实现卫星间的负载均衡，从而减少网络拥塞的发生。然而，这些研究仅仅关注GS与卫星之间单跳的性能，如切换次数、阻塞率、强制中断率、链路失败率等，而未考虑其对整个网络的影响。

LEO当前链路设置的依据

这一部分跟本文最开始说的一样:

1. 选 “剩余服务时间最长的”
2. 选 “距离最近的”
3. 选 “业务负载最轻”

Topology design in LEO mega-constellations. With the great potential of emerging LEO SNs to compete with today’s ISPs, many unique challenges have been given attention and discussed. A recent work [11] lists topology design as an interesting problem, but without a concrete analysis. Work in [13] gives a network topology design in inter-satellite network and assumes that as long as a GS is within range of a satellite, it can connect to it. However, no one has studied the satelliteground topology in such constellations as far as we know.

低轨（LEO）巨型星座中的拓扑设计。随着新兴LEO卫星网络（SNs）展现出与当今互联网服务提供商（ISPs）竞争的巨大潜力，许多独特的挑战已获得关注和讨论。近期一篇工作[11]将拓扑设计列为一个有趣的问题，但未进行具体分析。文献[13]给出了一种星间网络的拓扑设计，并假设只要GS处于卫星的覆盖范围内，便可以与之连接。然而，据我们所知，目前尚无人研究此类星座中的星地拓扑。

Routing protocols for LEO SNs. In view of the high dynamic but predictable characteristics of topology in LEO SNs, several routing protocols have been proposed specially for them. Routing based on virtual topology [15], [16], [22], [23], [25], [44]–[47] tackles the dynamic topology by discretetime network structure. The network topology is regarded as static at each time interval and the predicted topology or routing table calculated on the GS is uploaded to the satellite. Routing based on virtual node [21], [29], [30], [36], [37] calculates the next hop based on the pre-calculated relative position information between the satellites. Routing based on link state [39], [48] reduces the cost of link state flooding and the time of convergence using the predictability of satellite movement, based on the traditional link state routing protocol. However, these works pay more attention to the routing between satellites and have not explicitly proposed the setting of the satellite-ground topology.

适用于低轨（LEO）卫星网络的路由协议。 鉴于LEO卫星网络中拓扑高动态但可预测的特性，已有数种专门为其设计的路由协议被提出。基于虚拟拓扑的路由[15], [16], [22], [23], [25], [44]–[47]通过离散时间的网络结构来应对动态拓扑。网络拓扑在每个时间间隔内被视为静态，并在地面站上计算好预测的拓扑或路由表后上传至卫星。基于虚拟节点的路由[21], [29], [30], [36], [37]根据预先计算好的卫星间相对位置信息来计算下一跳。基于链路状态的路由[39], [48]在传统链路状态路由协议的基础上，利用卫星运动的可预测性来降低链路状态泛洪的成本和收敛时间。然而，这些工作更关注卫星间的路由，并未明确提出关于星地拓扑的设置。