面向火星临近空间时变信道的文件可靠传输机理

While the extremely long distance between Mars to Earth and sophisticated proximity space environment, the Martian surface detectors are unable to communicate directly to Earth. In order to overcome these constraints, the Mars Proximity Networks (MPN) is proposed, which have utilized store-and-forward communications system under Delay Tolerant Network (DTN) to increase data return from resource constrained landers. The sparsity and high-speed mobility in a large scale of MPN nodes, have challenged the reliable file delivery and buffer management simultaneity. The current deep space channel coding and conventional ARQ schemes are underperforming, where the high error bit rate and huge propagation delay in MPN environment, and spacecraft storing capabilities limitations. It motivated for using long erasure coding （LEC） systems in the transmission protocol level to provide a further level of protection with respect to conventional bit-level codes. The proposal is focus on the reliable file delivery over MPN, the Mars proximity channel and the statistics of the time-varying need to be researched firstly, to maximize the number of successfully transmitted bits. As Mars obiter divided the two different relay link, the LEC schemes need to be design separately to match the different quality of the link and equipment capacity, and joint optimization with the corresponding protocol layer in DTN. This will provide MPN file delivery a higher reliability, enhance the storage and resource utilization, and a simulation platform will be developed to verify the performance of the above algorithms and offer some improvement propositions.

火星探测任务极远的通信距离和复杂的临近空间环境使得表面探测设备无法直接向地球返回探测信息，需要构建火星中继轨道器构建临近空间网络，以中继存储转发的容迟网络体制传输数据文件。而火星临近空间网络的稀疏节点大范围高速移动，同时对文件可靠传输和节点存储资源提出了挑战。深空弱链路的大传播时延以及高误码率，使得传统的深空信道编码和确认重传机制无法满足未来深空探测的需求。随着面向传输层文件分组的长纠删码技术兴起，课题以保障火星临近空间文件可靠传输为切入点，首先对火星临近空间时变信道建模并研究统计特性，以获得节点间的最大吞吐量期望策略；然后针对以火星中继轨道器划分开的两段中继链路，分别设计匹配分段链路质量的差异和设备能力的长纠删编码并与相应的深空容迟网络下存储转发体制的协议层进行联合优化。在保障火星临近空间链路传输性能的同时，保障节点存储能力和资源利用率，并建立仿真验证平台修改和完善上述算法。

随着我国深空探测工程的持续深入，本项目基于我国空间科学技术的发展现状和未来深空探测的网络化趋势，针对未来火星探测任务所面临的极远通信距离及火星复杂临近空间环境等难题，探索了在未来的深空容迟/容断网络体制下的文件可靠传输机制。项目针对火星临近空间的信道时变、节点稀少、动态性高等特点，以构建火星临近空间网络为切入点，重点研究设计了长纠删码以保障探测数据分段可靠传输的机制，具体如下：.1）联合考虑地球-火星各段链路的节点缺少端到端路径和不同频段的传播特性，首先对火星临近空间信道建模，然后对网络体系架构的链路预算、协议栈及数据传输机制进行全面的测算与分析；研究信道时变机理和统计特性，评估了节点间允许传输的机率、存储转发的开销，建立了LEC复杂度与非纠删ARQ传输性能及信道环境参数的量化模型。.2）以中继节点的存储转发机制为核心，针对分段链路质量的差异和设备能力，设计不同的LEC分组处理机制，验证了纠删传输机制可靠性；对LEC与DTN传输协议体系进行联合优化设计，提高了传输的可靠性能和资源利用率，保障了大衰减、大时延环境下的文件可靠传输。.3）定量分析DTN框架下通信资源开销与业务传输的收益，联合考虑信道状态、能量分配、链路可见时间、节点计算能力和存储资源，设计节点资源联合优化的高效传输机制，优化大尺度深空网络的多跳保管传输机制，提升下行吞吐量，并搭建仿真平台进行综合评估验证。