空地网络协同信息分发的传输模型与关键技术

High data-rate media such as video has become the mainstream of mobile Internet services. Statistics showed that repeated transmission of hotspot content was the main reason leading to low transmission efficiency. To relieve the pressure of terrestrial networks, the basic idea of cooperative satellite-terrestrial content distribution is to broadcast hotspot content to users or their neighbors through satellites, then to send personalized content through end to end terrestrial networks to save satellite resources. However, the heterogeneity and unreliability of satellite broadcasting bring big challenges to space-terrestrial cooperative transmission. For high data-rate media services, considering its distortion-tolerant property, an uncoded satellite broadcasting technique is studied to solve the heterogeneous problem and to make the transmission more robust. Furthermore, a coded and uncoded cooperative transmission mechanism is also investigated to increase the transmission efficiency. As for lossless services, a raptor coding and rate compatible modulation based satellites broadcasting mechanism is proposed, which is enhanced with terrestrial retransmissions to improve system reliability. We will build a broadcasting and communication integrated service model, optimize the traffic distribution between satellite broadcasting and ground communication, and study a unified framework for the cooperative satellite-terrestrial network to ensure highly efficient and flexible transmission. Finally, a simulation platform will be developed to demonstrate and verify the proposed research. Aiming at some breakthroughs in theory and innovations in techniques, this research project is expected to provide a fundamental theory as well as technical solutions for establishing the framework of the cooperative satellite-terrestrial network.

视频等大容量媒体已成为移动互联网业务的主流，统计表明，热点内容的重复传输是导致传输效率低下的重要原因。空地协同信息分发的基本思路是将热点内容集结，通过卫星广播到用户或者靠近用户的节点，缓解地面通信网络压力，将小众内容通过地面通信网络端到端传输，减少卫星资源消耗。但卫星广播的异构性及不可靠性给空地协同传输带来了巨大挑战。针对大容量媒体业务，利用其失真可容忍特性，研究卫星无编码广播技术，解决异构性问题，进一步地，提出编码无编码协同传输机制，提高传输效率。对于无损业务，提出结合喷泉码和速率兼容调制的高效卫星广播机制，并通过地面通信网络补发来增强传输可靠性。建立广播与通信融合的服务模型，优化业务流量在卫星广播和地面通信网络之间的分配。研究统一的空地协同控制机制，保证空地协同传输的高效性和灵活性。最后，开发演示平台对研究成果进行验证。项目研究将为构建空地互联网协同体系架构提供理论基础和技术手段。

大容量媒体业务分发对网络带宽提出了巨大的需求，同时，热点内容的重复发送将显著降低传输效率。针对这一问题，本项目研究基于广播与通信融合的空地协同高效传输机制。项目的主要成果：1）在面向失真可容忍媒体的无编码空地协同传输的机制研究方面，得到了相关信源无编码传输的失真内界。针对空间网络图像视频传输，提出面向信道异构和分辨率异构的无编码传输框架和资源分配算法，并将无编码传输与非正交多址接入机制结合，有效提高了视频传输效率。针对空地协同传输，提出基于ICN SDN架构的空地协同网络，引入了空地协同缓存机制。2）在面向无损业务的信息传输方面，给出了不同信道条件下的RCM容量界及最佳权重集，进一步提出基于可变权重集的自适应传输机制。提出低并行度、大围长的双层准循环矩阵构造方法。提出对数译码和多单元译码等低复杂度译码算法。针对译码硬件负荷不均衡，提出部分并行分层译码架构。针对空间辐射对电路的干扰，提出高容错随机计算译码算法。设计出Gbit/s级吞吐率的译码器，译码时间正比于符号数量。为RCM在空间环境的实际应用奠定了坚实基础。3）在广播与通信融合的服务模型方面，热点信息以卫星广播进行传输，个性化信息以地面网络传输，提出了基于物理性质的波束设计方法，并通过对非正交多址接入的研究，建立资源分配双层博弈模型，显著提升网络信息容量。4）在演示验证系统搭建方面，面向海域远距离宽带无线通信的应用需求，研发了基于AIS信息的自适应波束成型发射机与接收机，并在烟台-大连海域通信平台开展试验，验证了其具有动态资源分配的宽带传输能力，传输距离可达100km。研究成果为构建空地互联网协同体系架构提供理论基础和技术手段。课题共发表学术论文72篇，其中包括IEEE Trans等SCI期刊论文37篇，申请发明专利23项，出版著作1部。