联合参差合并检测及优化子码映射的互补码多址通信方法

There exists serious selective fading in the channel of asynchronous communications between multiple low earth orbit (LEO) satellites and the ground, due to the multi-path fading and Doppler effect, which makes it hard to design a multiple access method with high interference-elimination capability. Owing to the multi-dimensional code structure, complementary codes (CCs) is able to achieve ideal correlation properties, which provides an interference-free code division multiple access method. However, such perfect orthogonality of CCs will be destroyed by diverse fading of sub-channels caused by selected fading and consequently the CCs-based multiple access technique will lose its theoretical interference-free feature. In this research topic, diverse contribution of multiple element sequences to the correlation peak over selective fading channels is analyzed. Based on such diverse features, a weighted-combining detection algorithm for complementary de-spreading is proposed according to the optimization theory and adaptive theory. At the same time, this research topic takes both the effect of selective fading channels on complementary correlation and the diversity gain hidden in selective fading channels as new constraints of code design. A new kind of weighted-complementary codes is proposed with new definition of weighted-complementary correlation. Then a joint optimized element sequences allocation and weighted-combining detection method with such new CCs is proposed, which will improve the bit error rate of the system over selective fading channels with enhanced capability of interference-elimination by taking full advantage of diversity gain over selective fading channels, as a valuable multiple access scheme for asynchronous communications between multiple LEO satellites and the ground.

低轨卫星的通信信道存在严重的不均衡及选择性衰落，亟需一种具有高干扰抵抗能力的多星星地异步通信多址方案。互补码是一种具有多维结构的码资源，其同时具有理想的自相关和互相关特性，进而提供了一种无干扰的码分多址方案。然而，互补码的理想正交性依赖于子码相关的等增益合并，选择性衰落引起的差异化子信道衰落将破坏互补码的正交特性，从而无法获得理论上的抗干扰能力。据此，本课题针对选择性衰落信道中互补码子码对于相关峰的差异化贡献特征，引入最优化及自适应理论，提出互补解扩的参差合并检测算法。同时，将选择性衰落对于互补相关的影响及选择性衰落能够带来的分集增益作为码的设计约束，构造一类新的参差互补码，并提出联合子码分配算法及参差合并检测的参差互补码多址通信方法，有效提高系统抵抗干扰能力的同时，利用选择性衰落的分集效应，提高系统在选择性衰落信道下的误码率性能，为低轨卫星多星星地异步通信提供一种有价值的多址方案。

低轨卫星通信信道存在严重的不均衡、选择性衰落及高时变特征，亟需一种具有高干扰抵抗能力的多星星地异步通信多址方案。互补码是一种多维结构扩频码，其同时具有理想的自相关和互相关特性，理论上可实现无干扰的码分多址通信。然而，实际低轨卫星通信系统中的选择性衰落等特征会破坏互补码的正交特性，从而无法获得理论上的抗干扰能力。.据此，本课题针对基于互补码理论的扩频通信系统在低轨卫星通信中的应用开展相关研究。项目首先通过理论分析揭示了传统互补码及相应系统设计的局限性，针对互补码各子码在选择性衰落信道下对于相关峰的差异化贡献进行分析，并基于该差异特征，通过引入最优化理论及自适应理论，提出了互补解扩的参差合并检测算法，有效的提高了系统抵抗多用户及多径干扰能力的同时，充分利用选择性衰落带来的分集效应，显著地提高系统的误码率性能。.在此基础上，项目提出将选择性衰落对于互补相关的影响及选择性衰落能够带来的分集增益作为码设计的约束，设计了一种新型的互补相关定义下具有理想相关特性的加权互补码的设计方法，实现了可以在完全消除多址干扰的同时获得频率选择性衰落所带来的全分集增益，进而获得了比现有互补码扩频系统更低的多用户误码率性能。.最后，本项目进一步针对互补码理论在低轨卫星通信中应用需要解决的相关问题进行了研究，提出了一种星载相控阵天线结合三维互补码的系统设计方案，并探索了上述通信系统中的星载相控阵天线设计、用于参差合并检测参数计算的相关参数估计、空时频资源优化管理等问题，推进了互补码理论在卫星通信中的应用，也为通信、侦察、遥感卫星载荷的一体化设计提供了新的研究思路和基本技术支撑。