Abstract Satellite range scheduling with the priority constraint is one of the most important prob lems in the field of satellite operation. This paper proposes a station coding based genetic algorithm to solve this p...Abstract Satellite range scheduling with the priority constraint is one of the most important prob lems in the field of satellite operation. This paper proposes a station coding based genetic algorithm to solve this problem, which adopts a new chromosome encoding method that arranges tasks according to the ground station ID. The new encoding method contributes to reducing the complex ity in conflict checking and resolving, and helps to improve the ability to find optimal resolutions. Three different selection operators are designed to match the new encoding strategy, namely ran dom selection, greedy selection, and roulette selection. To demonstrate the benefits of the improved genetic algorithm, a basic genetic algorithm is designed in which two cross operators are presented, a singlepoint crossover and a multipoint crossover. For the purpose of algorithm test and analysis, a problemgenerating program is designed, which can simulate problems by modeling features encountered in realworld problems. Based on the problem generator, computational results and analysis are made and illustrated for the scheduling of multiple ground stations.展开更多
为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通...为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通信钟差干扰;根据校正的需求,求解接收信道的最优方向角,优化用户接收终端的接收信道;在此基础上,结合OFDM信号特点,根据通信信号的发射周期,将信号划分为不同的时间窗;建立同步校正的度量函数,估计OFDM信号的符号起始位置,通过预估误差补偿实现了对钟差的同步校正。经过实验测试可知,应用该方法进行OFDM信号校正处理后,通信信号波形更加规律;应用该方法进行钟差校正后钟差值较小,提升了星地一体化通信用户接收终端钟差同步校正的准确度。展开更多
在设计拓扑时,如何分配每颗卫星上有限的通信终端建立通信链路,构建一个性能良好的网络拓扑,成为了一个重要的研究问题。以平均月球中继卫星到地面站路径距离最小为优化目标,以卫星携带的通信终端数目、月球中继卫星与地面站的连通性为...在设计拓扑时,如何分配每颗卫星上有限的通信终端建立通信链路,构建一个性能良好的网络拓扑,成为了一个重要的研究问题。以平均月球中继卫星到地面站路径距离最小为优化目标,以卫星携带的通信终端数目、月球中继卫星与地面站的连通性为约束条件,提出了基于竞争决策思想的链路分配算法(Link Assignment Algorithm based on Competitive Decision, LAA-CD)和基于模拟退火法的链路分配算法(Link Assignment Algorithm based on Simulated Annealing,LAA-SA),并与贪婪算法进行对比。仿真结果表明,LAA-CD和LAA-SA算法下所得拓扑的平均月球中继卫星到地面站距离均小于贪婪算法,且LAA-CD算法能够有效降低算法的时间复杂度。进一步对比了两种星座,发现相比拉格朗日轨道卫星星座,在月球极轨道卫星星座下所得拓扑具有更小的平均距离,为空间信息网络分配提供技术支撑。展开更多
As a result of the exponential growing rate of worldwide Internet usage, satellite systems are required to support broadband Internet applications. The transmission control protocol （TCP） which is widely used in the...As a result of the exponential growing rate of worldwide Internet usage, satellite systems are required to support broadband Internet applications. The transmission control protocol （TCP） which is widely used in the Internet, performs very well on wired networks. However, in the case of satellite channels, clue to the delay and transmission errors, TCP performance degrades significantly and bandwidth of satellite links can not be fully utilized. To improve the TCP performance, a new idea of placing a TCP spoofing proxy in the satellite is considered. A Novel Satellite Transport Protocol （NSTP） which takes advantage of the special properties of the satellite channel is also proposed. By using simulation, as compared with traditional TCPs, the on-board spoofing proxy integrated with the special transport protocol can significantly enhance throughput performance on the high BER satellite link, the time needed to transfer files and the bandwidth used in reverse path are sharply reduced.展开更多
文摘Abstract Satellite range scheduling with the priority constraint is one of the most important prob lems in the field of satellite operation. This paper proposes a station coding based genetic algorithm to solve this problem, which adopts a new chromosome encoding method that arranges tasks according to the ground station ID. The new encoding method contributes to reducing the complex ity in conflict checking and resolving, and helps to improve the ability to find optimal resolutions. Three different selection operators are designed to match the new encoding strategy, namely ran dom selection, greedy selection, and roulette selection. To demonstrate the benefits of the improved genetic algorithm, a basic genetic algorithm is designed in which two cross operators are presented, a singlepoint crossover and a multipoint crossover. For the purpose of algorithm test and analysis, a problemgenerating program is designed, which can simulate problems by modeling features encountered in realworld problems. Based on the problem generator, computational results and analysis are made and illustrated for the scheduling of multiple ground stations.
文摘为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通信钟差干扰;根据校正的需求,求解接收信道的最优方向角,优化用户接收终端的接收信道;在此基础上,结合OFDM信号特点,根据通信信号的发射周期,将信号划分为不同的时间窗;建立同步校正的度量函数,估计OFDM信号的符号起始位置,通过预估误差补偿实现了对钟差的同步校正。经过实验测试可知,应用该方法进行OFDM信号校正处理后,通信信号波形更加规律;应用该方法进行钟差校正后钟差值较小,提升了星地一体化通信用户接收终端钟差同步校正的准确度。
文摘在设计拓扑时,如何分配每颗卫星上有限的通信终端建立通信链路,构建一个性能良好的网络拓扑,成为了一个重要的研究问题。以平均月球中继卫星到地面站路径距离最小为优化目标,以卫星携带的通信终端数目、月球中继卫星与地面站的连通性为约束条件,提出了基于竞争决策思想的链路分配算法(Link Assignment Algorithm based on Competitive Decision, LAA-CD)和基于模拟退火法的链路分配算法(Link Assignment Algorithm based on Simulated Annealing,LAA-SA),并与贪婪算法进行对比。仿真结果表明,LAA-CD和LAA-SA算法下所得拓扑的平均月球中继卫星到地面站距离均小于贪婪算法,且LAA-CD算法能够有效降低算法的时间复杂度。进一步对比了两种星座,发现相比拉格朗日轨道卫星星座,在月球极轨道卫星星座下所得拓扑具有更小的平均距离,为空间信息网络分配提供技术支撑。
文摘As a result of the exponential growing rate of worldwide Internet usage, satellite systems are required to support broadband Internet applications. The transmission control protocol （TCP） which is widely used in the Internet, performs very well on wired networks. However, in the case of satellite channels, clue to the delay and transmission errors, TCP performance degrades significantly and bandwidth of satellite links can not be fully utilized. To improve the TCP performance, a new idea of placing a TCP spoofing proxy in the satellite is considered. A Novel Satellite Transport Protocol （NSTP） which takes advantage of the special properties of the satellite channel is also proposed. By using simulation, as compared with traditional TCPs, the on-board spoofing proxy integrated with the special transport protocol can significantly enhance throughput performance on the high BER satellite link, the time needed to transfer files and the bandwidth used in reverse path are sharply reduced.
