基于多技术融合的星地激光通信性能优化方法研究

At the beginning of 2017, the world's first 5.12Gbps coherent laser communication success in orbit test to make the level of China's space laser communications to the forefront of the world. But the on-orbit system modulation method is single,the lack of error detection and error correction measures, and the use of analog demodulation, it is difficult to meet the needs of the future "integration of heaven and earth information network" on the satellite laser communication rate and quality requirements. Based on this, the project intends to proceed from different communication technologies, trying to realize the optimization and upgrading of the performance of the satellite to ground laser communication through the innovative integration of channel coding, multidimensional modulation and digital receiving technology. In particular, firstly, by using the rateless code feature of Luby transform codes and optimizing the degree distribution function, we construct a channel coding and decoding method with strong error correction and short delay. Secondly, we focus on analyzing the adaptability of different modulation methods in atmospheric channel, research and construction of high power and bandwidth utilization multi-dimensional modulation method; Finally,the high sensitivity, fast digital coherent receiving method and processing algorithm in turbulent environment are explored. The smooth development of this project will strengthen the physical basis of high-speed, low-error transmission and real-time coherent demodulation of the satellite to ground laser link, and provide the necessary theoretical support and technical reserve for the development of the new generation of satellite to ground laser communication system.

2017年初，世界首次 5.12Gbps的星地相干激光通信成功在轨测试使我国空间激光通信水平跃居世界前列。但在轨系统的调制方式单一、缺乏检错纠错措施、且采用模拟解调方式，很难满足“天地一体化信息网”对星地激光链路通信速率和质量提出的要求。基于此，本项目拟从不同的通信技术着手，试图通过信道编码、多维调制及数字接收等技术的创新性融合，实现星地激光通信性能的优化和升级。具体而言，首先，利用LT码（Luby Transform codes）的无速率码特征，优化度数分布函数，构建检纠错能力强、延时短的信道编译码方法；其次，着重分析不同调制方式对大气信道的适应性，研究并构造功率和带宽利用率高的多维调制方法；最后，探索湍流环境下的高灵敏度、快速数字相干接收方法及处理算法。本项目将为星地激光链路信息的高速、低误码传输以及实时相干解调夯实物理基础，为新一代星地激光通信系统的发展提供必要的理论支撑和技术储备。

本项目主要从通信技术本身入手，充分考虑星地激光通信信道特征，开展了基于LT码（Luby Transform codes）的新型信道编译码方法、新型多维混合调制方法及相干探测接收等方面的研究，力求通过信道编码、调制技术、相干探测及处理方法的融合，实现星地激光通信系统性能全面优化的目标。具体而言：. 深入研究了两类喷泉码编码方案，设计新的度分布函数，提出了一种喷泉码码的译码方法，从新型度分布函数和改进译码方案两个角度，详细介绍了LT码在FSO系统中应用的性能优化方案。. 为了提升通信性能，对不同调制接收方案，尤其是不同的RF-FSO混合系统进行了深入研究。对空间分集合并接收的QAM/FSO系统、混合脉冲位置调制-二进制相移键控-副载波强度调制（PPM-BPSK-SIM）方案、混合LPPM-BPSK-SIM调制接收方案、混合脉冲位置调制二进制相移键控子载波强度调制（PPM-BPSK-SIM）方案等展开了系统研究。. 对不同光束特性进行了深入研究，为信号光束的选择提供了理论支撑。尤其是对径向极化的部分相干旋转椭圆余弦-高斯光束在大气湍流和自由空间的传输特性、Air艾里式高斯－赫尔米特－拉格勒－高斯波包的传播特性、同轴和离轴涡旋对的自聚焦线偏振圆皮尔西-高斯涡旋光束通过高数值孔径时的紧聚焦特性等，进行了全面系统分析。. 对涡旋光束通信系统构建、传输与接收进行了深入研究。提出了一种基于32通道的大气湍流混合多路复用、高数据传输能力的轨道角动量（OAM）通信系统及其测试方法；提出了基于卷积神经网络的OAM的识别算法；并用超构表面实现了多种OAM的产生方案。.