深空激光可靠通信的关键技术研究

Deep space optical communications, as the optimal scheme providing high data rate and capacity、low power consumption and high safety communications, its reliable operation has important meanings for improving the development of deep space exploration. However, how to realize the deep space optical reliable communications under the disadvantageous situations of long distance、weak signals、long time-delay、serious atmosphere effect、limited power, is the common difficult subject to human being. Based on the previous work, this project will intensively study source compression、channel coding、modulation technology and data transmission strategy, so as to provide theory basis for the optimized designs of deep space optical communication systems, and to provide technology support for the practical use of deep space optical communications. The specific contents are as follows:①establish compressed sensing based compressing coding and reconstruction algorithm for deep space images, so as to improve the resource utilization ratio and to lower the complexity of the system; ②construct LDPC codes with excellent performance and propose the decoding algorithm which can effectively eliminate trap sets and is close to maximum likelihood decoding algorithm, so as to reduce the complexity of coding and to improve decoding performance; ③establish transmission model with strong resistance to atmospheric effect of frequency modulation optical OFDM signals, and analyze its performance under the perfect atmospheric channel model, so as to improve information transmission rate and to ensure the reliable transmission of optical signals; ④ design the link-state awarded intelligent data transmission strategy, so as to effectively utilize link resources and to reduce the overhead of transmission control.

深空光通信是提供高数据率、大容量、低功耗、高安全性深空通信的最佳方案，其可靠运行对推动深空探测的发展具有重要意义。然而，如何在距离远、信号弱、时延大、大气影响严重、功率受限等不利情况下实现深空激光可靠通信是人类共同面对的技术难题。本项目拟在前期工作基础上，对信源压缩、信道编码、调制、数据传输策略等关键技术展开深入研究，为深空光通信系统的优化设计提供理论基础，为深空光通信的实际应用提供技术支撑。具体内容如下：①建立基于压缩感知的深空图像压缩编码与重构算法，提高系统资源利用率、降低系统复杂度；②构造性能优异的LDPC码并给出有效消除陷阱集且接近最大似然译码的译码算法，降低编码复杂度，提高译码性能；③建立强抗大气效应的调频光OFDM信号传输模型，分析其在完善大气信道模型下的性能，提高信息传输速率，保障激光信号的可靠传输；④设计链路状态感知的智能数据传输策略，有效利用链路资源，降低传输控制开销。

本项目深入研究了深空激光可靠通信的若干关键技术，主要包括基于压缩感知的图像压缩编码与重构、LDPC码的构造与译码算法、大气信道下光OFMD信号传输过程建模与分析、连接状态感知的数据传输策略。取得的主要研究成果如下：.(1)构造了基于奇异值分解的托普利兹结构矩阵和基于混沌扩频序列及块加权矩阵的观测矩阵，降低了观测系统的实现代价；建立了基于压缩感知的深空图像压缩编码模型，结合压缩编码模型的特点，提出了基于单层小波变换的鲁棒性重构算法。.(2）利用短环搜索算法和确定性数列构造了大围长QC-LDPC码，克服了短环对码字性能的影响；通过行列删除的方法实现了码率兼容，以准双对角结构与确定性构造方法实现了码字的快速编码，降低了编译码复杂度；采用原模图构造多进制LDPC码，降低了误码平层，提高了抵御随机和连续突发错误的能力。.(3）分析了光OFDM系统的特点及原理，搭建了光OFDM信号传输模型；提出了基于叠加训练序列的ACO-OFDM系统时间同步方法和基于线性最小均方误差和压缩感知的ACO-OFDM系统信道估计方法；研究了不同调制方式、不同大气湍流强度对光OFDM信号传输特性的影响。.(4）分析了深空光通信的链路可用性及信道对链路的影响，设计了满足深空光通信特性和要求的喷泉码编译码方案，并提出了基于喷泉码的深空多文件传输策略和基于优化接触图算法的深空路由设计方法，克服了长时间光往返造成的带宽浪费，在不可靠的物理链路上保证了数据的可靠传输。