基于训练序列的OFDM系统符号同步算法设计与实现

发布时间：2018-05-13 09:09

本文选题：基带 + OFDM　；参考：《东南大学》2017年硕士论文

【摘要】：随着移动通讯技术的全面普及与飞速发展,正交频分复用(OFDM,Orthogonal Frequency Division Multiplexing)技术作为一种多载波调制的高速传输方式,以其高效的频谱利用率,稳定的抗多径能力等优点,使之成为当前应用于第四代移动通信系统中的核心技术,并且在针对LTE芯片测试等方面也具有一定的应用价值。然而OFDM系统对符号同步的同步偏差具有很高的要求。因此符号同步的精确与否,对于OFDM系统性能的提升具有非常重要的作用。本文针对基于训练序列的OFDM符号同步算法进行研究与改进,综合了 SchmidlCox算法与Park算法在训练序列上的一致性以及它们在性能上的互补关系,对OFDM符号同步方法提出了改进方法,该方法的整个同步环节由粗同步估计和精同步估计两个阶段构成。首先运用SchmidlCox的算法进行一个粗略的同步估计。然后以粗略同步估计的位置来确定精同步估计阶段的估计窗口,最后以Park算法的方式进行精符号同步估计得到最终确定的符号定时的位置。Matlab的仿真结果表明改进算法的同步均方误差(MSE,Mean Square Error)在高信噪比和低信噪比情况下相对于现有算法均保持在较低水平。关于OFDM符号同步算法的硬件实测从功能和性能指标两个方面展开,结果表明,基于FPGA平台实现的改进算法能够实现对OFDM基带信号进行符号同步的功能,并可以绘制出相应的星座图。在误差矢量幅度(EVM,Error Vector Magnitude)指标上,通过将OFDM系统中FFT模块的输出数据导入至Matlab中计算,EVM的计算结果在5%以下。在MSE指标上,通过在Matlab中对同步误差值进行统计与计算,MSE在SNR小于8dB时计算结果在105以下,MSE在SNR大于8dB时计算结果在10以下,且均优于现有算法。本文的OFDM符号同步估计方法在功能和性能上均满足了设计要求和指标,可实现OFDM基带系统中对信号的符号同步,其研究成果对于应用OFDM技术的通信系统具有一定的工程实用价值。
[Abstract]:With the popularization and rapid development of mobile communication technology, orthogonal Frequency Division Multiplexing) (orthogonal Frequency Division Multiplexing) technology, as a high speed transmission mode of multi-carrier modulation, has the advantages of efficient spectrum efficiency and stable anti-multipath capability. It has become the core technology applied in the fourth generation mobile communication system, and also has certain application value in the field of LTE chip test and so on. However, the synchronization deviation of symbol synchronization in OFDM system is very high. Therefore, the accuracy of symbol synchronization plays a very important role in improving the performance of OFDM system. In this paper, the algorithm of OFDM symbol synchronization based on training sequence is studied and improved. The consistency of SchmidlCox algorithm and Park algorithm in training sequence and their complementary relationship in performance are synthesized, and the improved method of OFDM symbol synchronization is proposed. The whole synchronization of this method consists of rough synchronization estimation and precision synchronization estimation. First, a rough synchronization estimation is made by using SchmidlCox algorithm. Then the estimation window of the precise synchronization estimation stage is determined by the rough synchronization estimation position. Finally, the position of the final symbol timing is estimated by using Park algorithm. The simulation results of Matlab show that the improved algorithm has high SNR and low SNR relative to MSE mean Square error in the case of high signal-to-noise ratio (SNR) and low signal-to-noise ratio (SNR). The existing algorithms are kept at a lower level. The hardware measurement of OFDM symbol synchronization algorithm is carried out from two aspects: function and performance index. The result shows that the improved algorithm based on FPGA platform can realize symbol synchronization of OFDM baseband signal. And can draw the corresponding constellation map. On the index of error vector amplitude, the output data of FFT module in OFDM system are imported into Matlab. The result of calculation is less than 5%. In terms of MSE index, the synchronous error value in Matlab is counted and calculated. When SNR is less than 8dB, the calculated result is less than 10 when SNR is larger than 8dB, and it is better than existing algorithms. The OFDM symbol synchronization estimation method in this paper meets the design requirements and specifications in function and performance. It can realize the symbol synchronization of signals in the OFDM baseband system. The research results have certain engineering practical value for the communication system using OFDM technology.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.53

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