MIMO-OFDM盲时频同步技术研究

发布时间：2018-03-17 10:44

本文选题：多输入多输出　切入点：正交频分复用　出处：《西安电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来,无线移动通信技术和相关应用开始蓬勃发展起来,但是频谱资源不足问题已经成为阻碍其发展的瓶颈。如何在保证传输可靠性的前提下提高系统频谱效率和信道容量已成为无线通信领域研究的焦点。多输入多输出(MIMO)依靠空间复用技术可以提高数据传输速率,增加信道容量。正交频分复用(OFDM)是一种特殊的多载波调制技术,它的每个子载波之间相互正交,可以提供更高的频谱利用率。MIMO-OFDM系统同时具备二者的优势方面,然而该系统对同步误差非常敏感,非理想同步往往会显著降低系统性能,因此精确的时间和频率同步对该系统来说尤为重要。本文旨在探讨集中式非合作MIMO-OFDM系统在移动无线信道下的盲时频同步技术,主要工作如下:1.首先对MIMO通信系统模型及其信道容量、OFDM技术基本原理及其优缺点进行了阐述;其次对MIMO-OFDM系统模型及其所涉及的主要关键技术进行了重点介绍;最后,对移动无线信道进行了详细的阐述并进行了数学建模。2.建立了非合作MIMO-OFDM无线通信系统模型。从系统时域信号模型出发,对非理想定时同步对解调信号的影响进行了理论分析,并对结果进行了计算机仿真验证。同时还介绍了现有合作MIMO-OFDM通信中常用的Mody和ZelstSchenk符号定时同步算法。3.针对MIMO-OFDM物理帧结构的循环前缀特性,设计了一种有效符号长度盲估计算法。分析了最大似然定时同步算法的不足并对针对它进行改进,提出了基于延迟相关集系数的盲帧长与定时同步联合估计算法。首先定义延迟相关集系数,然后将它与帧长在正常取值的有效范围内进行二维搜索,从而确定物理帧长度,并根据此时延迟相关集系数随采样点位置所呈现的变化规律确定定时同步位置,最后通过仿真验证了提出算法的有效性和可靠性。4.分析了非理想频率同步对MIMO-OFDM系统的影响,介绍了现有合作通信中常用的频偏估计方案。通过对多径信道下接收信号模型所具有的数学性质进行深入分析,提出了一种基于聚类的自适应MIMO-OFDM盲时频同步算法,该算法不需要信道参数、空时编码类型等先验信息,可以克服多径的影响,估计性能较好。最后,通过MATLAB仿真验证了该算法能够在非合作移动通信场景下实现高精度的时频同步。
[Abstract]:In recent years, wireless mobile communication technology and related applications began to flourish, However, the problem of insufficient spectrum resources has become the bottleneck that hinders its development. How to improve the system spectrum efficiency and channel capacity under the premise of ensuring the transmission reliability has become the focus of research in the field of wireless communication. Using spatial multiplexing technology can improve the data transmission rate. Increasing channel capacity. Orthogonal Frequency Division Multiplexing (OFDM) is a special multicarrier modulation technology. Each of its sub-carriers is orthogonal to each other, which can provide a higher spectrum efficiency. MIMO-OFDM system has the advantages of both. However, the system is very sensitive to synchronization errors, and non-ideal synchronization often significantly reduces the performance of the system. Therefore, accurate time and frequency synchronization is particularly important for the system. This paper aims to discuss the blind time-frequency synchronization technology for centralized non-cooperative MIMO-OFDM systems in mobile wireless channels. The main work is as follows: 1. Firstly, the basic principle, advantages and disadvantages of MIMO communication system model and its channel capacity are described. Secondly, the MIMO-OFDM system model and its main key technologies are introduced emphatically. In this paper, the mobile wireless channel is described in detail and the mathematical model is established. The model of non-cooperative MIMO-OFDM wireless communication system is established. Based on the time-domain signal model of the system, the influence of non-ideal timing synchronization on the demodulation signal is analyzed theoretically. The results are verified by computer simulation. At the same time, Mody and ZelstSchenk symbol timing synchronization algorithms, which are commonly used in cooperative MIMO-OFDM communication, are introduced. 3. The cyclic prefix characteristics of MIMO-OFDM physical frame structure are discussed. An effective blind symbol length estimation algorithm is designed, and the shortcomings of the maximum likelihood timing synchronization algorithm are analyzed and improved. A joint estimation algorithm of blind frame length and timing synchronization based on delay correlation set coefficient is proposed. Firstly, the delay correlation set coefficient is defined, and then two-dimensional search is carried out with the frame length in the valid range of normal values to determine the physical frame length. The timing synchronization position is determined according to the variation of the delay correlation set coefficient with the sample location. Finally, the validity and reliability of the proposed algorithm are verified by simulation. Finally, the influence of non-ideal frequency synchronization on the MIMO-OFDM system is analyzed. This paper introduces the frequency offset estimation schemes commonly used in cooperative communication. By analyzing the mathematical properties of the received signal model in multipath channel, an adaptive MIMO-OFDM blind time-frequency synchronization algorithm based on clustering is proposed. The proposed algorithm does not require prior information such as channel parameters, space-time coding types and so on. It can overcome the influence of multipath and has good estimation performance. Finally, The simulation results of MATLAB show that the proposed algorithm can achieve high precision time-frequency synchronization in non-cooperative mobile communication scenarios.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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