【作者】 童圣洁；

【导师】 李红信；

【作者基本信息】 兰州大学 ， 通信与信息系统， 2008， 硕士

【摘要】 正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)作为多载波调制技术的之一,是当前一种非常热门的通信技术,也被公认为是第四代移动通信(4G)的核心技术之一。它具有抗多径衰落和频谱利用率高的特点,被广泛用于高速数字通信领域。但作为一种利用正交子载波的多载波调制技术,OFDM对于频偏非常敏感,因此,如何获得可靠的同步信息成为OFDM研究中的关键。对于OFDM的同步算法而言,主要沿袭两条思路,分别是基于数据辅助型的算法和非基于数据辅助型的算法。论文的研究方向是对前一大类算法的研究和仿真分析,主要的工作有以下几点。(1)在MATLAB/SIMULINK中构建基本OFDM系统的仿真模型。(2)针对数据辅助型算法中最经典的最大似然估计算法(MaximumLikelihood,ML)和SC算法进行理论研究和算法仿真。先通过理论分析找出其各自的不足之处,再通过MATLAB对各个算法进行编码实现,最后仿真验证在理论推导时所取得的相关结论。(3)通过经典算法的启示,引入介绍一种新的同步算法,此算法相对于SC算法而言在定时同步点的确定这一方面有着明显的改进。同样,先通过理论分析对该算法进行简单的推导计算,再通过MATLAB编码实现该算法,最后仿真验证其改进性能。(4)通过定时同步图形与频偏标准差对三种算法进行比较。更多还原

【Abstract】 Orthogonal Frequency Division Multiplexing (OFDM), a special form of multicarrier modulation (MCM), has recently received considerable attention as well as be considered as the core technique of the forth mobile communication. It’s be widely used in high speed digital communication for its robustness to multipath selective fading and high bandwidth efficiency.As a kind of multicarrier modulation using orthogonal sub carriers, OFDM is sensitive to frequency offset and the time synchronization error. The key problem is acquiring the synchronization information. There are two kinds of synchronization algorithm, basing on date and un-basing on data. This paper focus on the front one. The tasks of this paper are four points.(1) Build a model for basic OFDM system in MATLAB/SIMULINK.(2) Analyze ML algorithm and SC algorithm and then realize them with programming in MATLAB. Finally, find the shortcuts of them.(3) A new improved algorithm based on SC algorithm is introduced and analyzed. As the result, the programmed algorithm will improve the time synchronization of SC algorithm.(4) These three algorithms are compared in two aspects, the figure of time synchronization and Standard Deviation of frequency offset.更多还原