《OFDM论文：OFDM快变信道多普勒分集技术》由会员分享，可在线阅读，更多相关《OFDM论文：OFDM快变信道多普勒分集技术（3页珍藏版）》请在金锄头文库上搜索。
1、OFDM论文：OFDM快变信道 多普勒分集技术【中文摘要】由于具有信道频谱利用率高、实现容易 （可采用快 速傅立叶变换）等优点，正交频分复用（OFDM技术已成为高速数据传 输的关键技术，并被纳入第四代移动通信参考标准。然而，OFDM系统 对频率偏差非常敏感，尤其在高速移动环境下，用户移动速度快，导致 信道的时变特性更加明显，多普勒频移和多普勒扩展更加显著，频率 偏差使OFDM系统子载波间的正交性遭到破坏，产生子载波间干扰 （ICI）,这将大大降低系统性能。本文从分集技术对抗多普勒效应和对 OFDM系统性能的影响入手，研究高速移动环境下OFDMS带通信。本 文首先研究高速无线信道的物理特性和数学
2、模型，描述各种衰落信道 的特性,分析信道的时变特性对传输信号频谱的影响，给出了几个描 述衰落信道的常用函数，特别分析了高速移动环境下OFDM系统的关 键问题。随后介绍了 OFDM系统的基本原理及分集技术，分析了 OFDM 传输系统的基本原理，推出了 OFDh时域和频域的模型，然后介绍了 OFDM系统的优点和缺点，最后介绍了分集技术，着重讨论了比较常用 的几种分集方式。研究了它们各自的优缺点，最终得出分集技术的一 般实现规律和特点。本文主要研究内容是多普勒分集技术，把多普勒扩展作为频域分集资源，这样不但可以克服多普勒扩展对 OFDM系统 的不利影响，还可以通过分集获得系统性能的提高。在接收端,针
3、对高 速移动环境下多普勒扩展明显的特性，研究了 OFDI系统中的多普勒 分集技术,分析了一种适用于OFDM系统的简化多普勒分集技术，同时也研究了 MIMO-OFD系统的多普勒分集技术。通过仿真，得出多普勒 分集技术和发射分集相结合可以更好的提高系统性能。在发射端，根 据高速列车通信的特点，提出了基于固定轨道的多普勒发射分集技术 同时提出了未来高速移动通信的宽带OFDM军决方案,在现有的TD-SCDM的高速铁路解决方案的基础上，解决应用多普勒分集技术的 难题,仿真结果表明，该技术有很大的优越性。【英文摘要】 Because of the high spectrum efficiency,ease
4、of implementation (via Fast Fourier Transform) and so on, orthog onal freque ncy divisio n multiplex ing (OFDM) tech no logy has becomethe key tech no logy of high-speed data tran smissi on, and has bee n adopted by the fourth gen erati on mobile com muni cati on. But OFDMystems are very sen sitive
5、to freque ncy deviati on, particularly in high-speed mobile en vir onment.Because the user moves fast, the channel s time-varying characteristics is obvious, the Doppler shift and Doppler spread are significant.These cause the frequency offset, thusthe orthog on ality betwee n OFDM sub-carriers is d
6、estroyed, which results in inter-carrier interferenee(ICI) and greatlyreduces the system performanee. In this thesis we focus on the Doppler effects which affect OFDkftignificantly,and study keytech no logies of OFDM in high-speed mobile com muni cati ons.ln this thesis we study the physical propert
7、ies and mathematicalmodel of high-speed wireless cha nn els, describe the characteristics of several fadi ng cha nn els, and an alyze the impact of time-vary ing cha nnel on sig nal spectrum. We an alyze several com mon fadi ng cha nn els fun cti on, and mainly focus on the key tech niq ues of OFDM
8、systems un der high-speed mobile en vir onment. The n we in troduce the OFDM systems basic principle and diversity techniques, give OFDM time domain and freque ncy domai n model, and discuss the OFDM systems adva ntages and disadva ntages. Fin ally we in troduce diversity tech niq ues and several co
9、m monly used methods. The adva ntages and disadva ntages of diversity are an alyzed, and the gen eral rules and characteristics of diversity tech niq ues are give n. The mai n word of this thesis is Doppler diversity tech no logy. Wetake the Doppler spread as a freque ncy diversity resource, which n
10、ot only overcomes the impact of Doppler spread on OFDM systems, but also improves the performa nee of system through diversity. At the receiver, we study Doppler diversity for OFDM systems under high-speed mobile environment, analyze a simplified Doppler diversitytech no logy for OFDMystems, anddiscuss the Doppler diversity tech no logy for MIMO-OFDsystems. Simulatio n results show the Doppler diversity tech niq ues comb ine with tran smitter diversity can improve the system
