OFDM系统中FFT的实现与信道估计算法研究

【作者】 刘青；

【导师】 余燕平； 王匡；

【作者基本信息】 浙江大学 ， 信息与通信工程， 2006， 硕士

【摘要】 在宽带无线移动通信的发展中,正交频分复用技术(OFDM)正因为其优越的性能而备受人们关注。OFDM技术已经成功的在数字音频广播(DAB)、地面数字视频广播(DVB—T)、无线局域网等领域得到应用。随着人们对通信数据化、宽带化、个人化和移动化的需求,OFDM技术在综合无线接入领域将越来越得到广泛的应用,已经被认为将会是4G移动通信的核心物理层技术。 本文将主要以DVB—T标准的传输方案为信号模型,对OFDM系统的接收机算法实现进行研究,重点放在其中的FFT处理模块和信道估计模块方面。 本文的结构如下: 第一章绪论介绍了数字通信的基本原理,无线信道的传播特点,以及OFDM技术发展背景知识。 第二章介绍了OFDM系统的基本原理。结合系统模型,对OFDM系统的各个部分的原理、实现方法进行了基本的分析。另外,由于本文的模型主要是针对DVB-T标准的,所以在本章的最后也简单给出了DVB-T的传输方案。 第三章对快速傅里叶变换(FFT)的实现算法,尤其是硬件实现方案进行研究。在分析了现有的各种基本算法的基础上,提出了一种高速FFT处理器的实现方案,其中在旋转因子的存储读取控制,以及蝶型处理单元的流水结构等方面进行了算法改进工作,减小了ROM的存储量,提高了蝶型运算单元的运算了效率。 第四章重点讨论了信道估计的实现算法。在简要介绍了信道估计原理后,着重对插值信道估计算法进行了研究,参照基本的插值理论,提出了一种改进的级连二维插值估计方法,在保持较低实现复杂度的条件下改进了基本插值方法的估计误差性能,并在信道估计后进行均衡与ICI的消除工作,进一步减小估计结果的误差。 第五章将是对全文的总结以及对今后工作的展望。更多还原

【Abstract】 The technology of orthogonal frequency division multiplexing (OFDM) has attracted a lot of focus for its excellent performance in the field of broadband wireless mobil communication systems. OFDM has been successfully applied in DAB, DVB-T and WLAN. Because of the demand for digitlized data, broadband personalized and mobile communication, OFDM has used in more and more applications in integrated wireless access communication field. It has been thought as the core physical layer technology of 4G mobile communications.This paper is a research about the algorithms of OFDM receiver, especially about the FFT process and channel estimation module. The signal model in this paper is the DVB-T standard.This paper is organized as follows:Chapter one, as a introduction, gives the brief concept of digital communication, the character of wireless channel and the development of OFDM.Chapter two describes the fundamental theory of OFDM. According to the syetem model, a basic theoretical analysis about principles and implementations of the main parts of OFDM syetem is given. The scheme of DVB-T is also presented in detail since our system is associated with DVB-T standard.Chapter three provides the related aigirithms of FFT processor design in OFDM receiver. First, the basic algorithms and structures are analyzed. Then, an effective implementation scheme of the FFT processor is presented, in which the algorithm about generation of twiddle factor and structure of butterfly computation is improved. The result shows that it reduces the needed memory of twiddle factor and increases the efficiency of the butterfly computation.Chapter four is mainly about the algotithm of channel estimation. After the analysis and comparison of the basic channel estimation interpolation algorithm, a novel 2-D interpolation aigorithm of channel estimation with low complexity is presented. The simulation results show that it has a better performance compared with traditional interpolation methods. Besides, an equalization and ICI cancellation module is used after channel estimation to improve the syetem’s performance.In Chapter five the work of this thesis is summarized and some notions for the future research are given.更多还原