优化卫星数传链路效率的VCM流程设计

摘要

为提高探测卫星数据传输链路的传输效能，采用可变编码调制体制（ VCM），在不增加卫星与地面站能量消耗和设备成本的条件下，降低链路资源浪费，优化星－地数据传输的吞吐量。在卫星VCM数传体制的基础上，分析了近地轨道卫星数传链路的动态链路预算，并详细讨论了链路传输效能的数学模型，给出了一种在有效数传时间内优化数传吞吐量的VCM流程设计算法。结果表明：该算法对于预知轨道的卫星系统，根据其动态的星－地链路预算结果，在保证误码率要求的前提下，选用不同的编码调制方式，从而拟合链路预算曲线，保持较为固定的链路余量，实现链路效率的优化；根据所述流程算法，针对一颗近地太阳同步轨道卫星设计VCM数传系统。通过数值仿真，与传统固定编码调制设计对比，说明这种VCM设计在提高链路有效性方面的突出优势。%The dynamic link budget of low earth orbit ( LEO) satellite data transmission link is analyzed, and the mathematical model of link efficiency is discussed. In order to enhance the data transmission link performance for exploration satellites, Variable Coding Modulation ( VCM ) system is applied to reduce link resource waste and improve the satellite⁃ground transmission throughput without increasing power consumption and design cost. A VCM schedule designing algorithm is illustrated for optimizing link throughput within the data transmission period. For a satellite system with foreseeable orbit and based on its dynamic link budget results, the proposed algorithm selects variable coding modulation combination under the bit error rate requirement to fit the link budget curve and keep a relatively constant link margin to achieve optimal link efficiency. Finally, on the basis of the proposed algorithm, a VCM data transmission system is designed for a LEO sun⁃synchronous satellite. According to the simulation results, the remarkable advantage of the proposed method is proved by comparison with traditional constant coding modulation design.