The Ka inter-satellite link (ISL) has been applied in the new generation of the BeiDou Navigation Satellite System. The next move is to supplement laser ISLs to improve the communication rate and ranging accuracy. A key challenge of the hybrid inter-satellite link network is how to properly schedule the two kinds of inter-satellite links to achieve better system performance, such as robustness, short transmission delay, and the position dilution of precision (PDOP). To solve this problem, we propose a compatible scheme of the laser/radio inter-satellite link network. The topology of the laser network is optimized based on maximum connectivity and minimum time delay through a multi-objective simulated annealing algorithm. Thereafter, a two-step algorithm optimizing the downlink delay and the PDOP is presented to arrange radio inter-satellite links. The proposed method was tested in a simulated case of the BeiDou Navigation Satellite System. The optimized topologies of the laser network reached the upper limit of connectivity, which was 2 in the simulated case, and downlink delay less than 0.3 s. Compared to the radio inter-satellite link network, the hybrid one enabled higher throughput of laser satellites (more than 125 Mbps), less downlink delay (less than 10 s), and smaller average weighted position dilution of precision (WPDOP) of laser satellites (less than 1.5 for IGSOs and less than 1 for MEOs).

中文翻译：

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导航卫星系统中激光/无线电混合网络的卫星间链路分配

Ka星际链接（ISL）已应用于新一代北斗导航卫星系统。下一步是补充激光ISL，以提高通信速率和测距精度。混合星际链路网络的关键挑战是如何正确调度两种星际链路，以实现更好的系统性能，例如鲁棒性，短传输延迟和精确位置稀释（PDOP）。为了解决这个问题，我们提出了一种激光/无线电卫星间链路网络的兼容方案。通过多目标模拟退火算法，基于最大的连接性和最小的时间延迟来优化激光网络的拓扑。此后，提出了一种优化下行链路延迟和PDOP的两步算法，以安排无线卫星间链路。该方法在北斗导航卫星系统的模拟情况下进行了测试。激光网络的优化拓扑达到了连接的上限，在模拟情况下为2，下行链路延迟小于0.3 s。与卫星之间的无线电链路网络相比，混合卫星可实现更高的激光卫星吞吐量（大于125 Mbps），更少的下行链路延迟（小于10 s）以及较小的激光卫星平均加权位置精度稀释（WPDOP） （对于IGSO，小于1.5，对于MEO，小于1）。