基于Grassmann流形的非相干酉空时调制解调算法研究

发布时间：2018-05-15 15:28

本文选题：酉空时星座图 + 酉空时调制　；参考：《华中科技大学》2014年硕士论文

【摘要】：多输入多输出（MIMO）调制技术可以提供空间分集增益和空间复用增益，它能够有效提高频谱利用率和信道容量，是目前4G和未来移动通信的关键调制技术。为了适应在高速移动的快衰落信道通信环境，Marzetta和Hochwald提出了非相干酉空时通信系统，该系统在调制和解调过程中不需要获取信道状态信息（CSI），因而无需占用信道带宽来发射导频信号。通过论证得出信道容量可达的非相干酉空时发射信号矩阵具有酉矩阵结构，Zheng等人将Grassmann流形这一数学工具引入到非相干酉空时通信的研究中，认为酉空时星座图的每一个星座点对应于Grassmann流形上的一个点。本文在国家自然科学基金项目“非相干MIMO通信系统编码调制关键技术研究”的资助下，重点研究了基于Grassmann流形的酉空时调制解调算法，提出了对跖结构酉空时星座图的设计方法及对跖结构酉空时星座图调制的简化解调算法。 1）本文提出Grassmann流形上的酉空时矩阵框架结构，在该框架约束下，以Frobenius弦距离作为星座图构造的距离准则，通过设置合适的步长来改变酉矩阵中每个元素的幅值和相位，在Grassmann流形上搜索最小Frobenius弦距离大于阈值的星座点，并将该星座点的对跖点也纳入星座图中，从而构造L个星座点的酉空时星座图。仿真实验表明，用这种次优的搜索算法所得到的星座图与文献中已经发表酉空时星座图相比，具有更好的性能。 2）针对Grassmann流形上非相干酉空时调制对跖星座图的结构特征，提出并证明了Grassmann流形上任意一对对跖点之间存在确定的恒等关系，，并且在此基础上提出了基于最大似然的非相干酉空时码的简化解调算法，仿真实验表明该解调算法在计算复杂度比最大似然解调算法降低一半的情况下，性能保持不变。因此，该简化方案是一种最优解调算法。
[Abstract]:Multi-Input-Multiple-Output (MIMO) modulation technology can provide spatial diversity gain and spatial multiplexing gain. It can effectively improve spectrum efficiency and channel capacity. It is a key modulation technology for 4G and future mobile communications. An incoherent unitary space-time communication system is proposed to adapt to fast fading channel communication environments in high-speed mobile systems, such as Marzetta and Hochwald. In the process of modulation and demodulation, the system does not need to obtain channel state information (CSI), so it does not need to take up the channel bandwidth to transmit pilot signals. It is proved that the incoherent unitary space-time transmit signal matrix with reachable channel capacity has unitary matrix structure and Zheng et al. The mathematical tool of Grassmann manifold is introduced into the study of incoherent unitary space-time communication. It is considered that every constellation point of unitary space-time constellation graph corresponds to a point on the Grassmann manifold. In this paper, a unitary space-time modulation and demodulation algorithm based on Grassmann manifold is studied, supported by the National Natural Science Foundation of China, "Research on key Technologies of coding and Modulation in incoherent MIMO Communication system". This paper presents a design method of unitary space-time constellation with metatarsal structure and a simplified demodulation algorithm for modulation of unitary space-time constellation with metatarsal structure. 1) in this paper, the unitary space-time matrix frame structure on Grassmann manifold is proposed. Under the constraint of this framework, the Frobenius chord distance is used as the distance criterion of constellation diagram, and the amplitude and phase of each element in the unitary matrix are changed by setting the appropriate step size. The constellation points whose minimum Frobenius chord distance is greater than the threshold value are searched on the Grassmann manifold, and the corresponding metatarsal points of the constellation point are also included in the constellation diagram, so as to construct the unitary space-time constellation map of L constellation points. The simulation results show that the constellation diagram obtained by the sub-optimal search algorithm has better performance than the unitary space-time constellation map published in the literature. 2) in view of the structural characteristics of non-coherent unitary space-time modulation (STM) pairs of constellations on Grassmann manifolds, a definite identity relationship between any pair of pairs of metatarsal points on Grassmann manifolds is proposed and proved. On this basis, a simplified demodulation algorithm based on maximum likelihood for incoherent unitary space-time codes is proposed. The simulation results show that the performance of the proposed demodulation algorithm remains unchanged under the condition that the computational complexity is reduced by half as compared with the maximum likelihood demodulation algorithm. Therefore, the simplified scheme is an optimal demodulation algorithm.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN919.3

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