滤波多音调制系统中的信道估计技术研究

【作者】 魏慧玲；

【导师】 高振明；

【作者基本信息】 山东大学 ， 通信与信息系统， 2005， 硕士

【摘要】 未来无线移动通信系统的目标是实现实时无缝的高质量、高速率的移动多媒体和数据业务传输。但是无线环境中存在的多径等特性造成系统严重的符号间干扰,同时无线移动信道的时变特性使得接收机难以准确跟踪信道特性。多载波调制(Multi-Carrier, MC)技术具有良好的抗多径能力和克服ISI的能力,因而近年来获得了深入研究和广泛应用,其中OFDM是一种特殊的多载波调制技术,已经被多个标准采用,并很有可能被采用到第4代宽带移动通信(4G)中。但是OFDM也存在一些固有缺点,例如在传输中它的正交性易受破坏,对频偏比较敏感,而且峰均比较高,从而需要大量的开销(CP和虚载波等),并且需要较为严格的定时同步等措施来保证系统性能。为了克服OFDM中的这些缺点,本文研究了一种新的正交多载波调制技术——滤波多音调制(FMT)在无线通信中的应用,并就其中的信道估计问题进行了研究。 滤波多音(Filtered Mutitone, FMT)调制技术是一种使用滤波器组的多载波调制技术。该技术使用滤波器组将整个信道划分为若干个子信道,使用多个子载波在这些子信道上进行信息的并行传输。然后在接收端采用匹配滤波器组对信号进行分离。其相邻子信道的信号之间频谱互不重叠,从而使得信道间干扰(ICI)非常小,甚至比系统中的其它噪声还要低,达到可以忽略的水平。但是由于在实际应用中,发送和接收滤波器不完全匹配,导致系统中存在较为严重的符号间干扰(ISI),因此在FMT系统中,滤波器组均衡是不可缺少的。目前FMT技术已经在VDSL中得到了广泛的应用,表现出良好的特性。 本文主要研究FMT系统在无线环境中的应用。首先分析介绍了无线信道的特性、无线通信的研究现状和OFDM系统的优缺点,并建立了无线FMT系统信道模型,阐述了FMT系统的基本原理,并且在与OFDM进行对比研究之后,着重研究了FMT的信道估计技术。文中首先研究了LS估计和使用扩频序列的估计方法,基于此提出了对使用扩频序列估计的改进方法,并对这些算法进行了计算机仿真和性能分析,之后分别对这三种信道估计算法作了性能更多还原

【Abstract】 The future mobile communication is intended to provide real-time and seamless mobile multimedia and data transmission service with high quality and high speed. But the features such as multi-path can lead to serious inter-symbol interferences and the time-variance make it difficult for the receiver to follow the channel features exactly. Because of its robustness to multi-path delay and ISI, multi-carrier modulation technique is well developed and widely used. OFDM has been adopted in several standards, and it is very likely to be adopted in the 4th generation wide band mobile communication. But OFDM has intrinsic disadvantages. For example, its orthogonality is easily to be destroyed, so it needs a lot of overheads (such as CP and virtual carrier) and strict timing synchronization is needed to ensure the performance of the system. To overcome the shortcomings, we investigate the use of a new orthogonal multi-carrier modulation technique, the method of filter banks multi-tone modulation, in wireless communication, especially in the field of the channel estimation.Filter banks multi-tone (FMT) modulation technique is a multi carrier modulation technique with filter banks. It divides the whole channel into several sub-channels with filter banks, and transmits the data information parallel with several sub-carriers. The frequency of neighboring sub-channel is not overlapped, so ICI is so lower even than other noise that we can ignore it in the FMT system.In this thesis, we first introduce the wireless channel, the research status of the wireless communication and the advantages and disadvantages of OFDM, and then we establish the channel model for wireless FMT system, and interpret the basic principles of FMT system, and make a comparison with OFDM, then concentrate on the study of FMT channel estimation method. The channel estimation will be introduced in time domain. Least Square estimation and the estimation with Spread Sequence are studied simulated with computer and compared in performance first, then the improved channel estimation method withSpread Sequence is provided. The performance comparison of these three channel estimation methods indicates that the channel estimation for FMT system in time domain is simple but effective, and the performance of the channel estimation with Spread Sequence is better than that of LS channel estimation. The improved method reaches a better performance. At last the space-time joint channel estimation method for FMT system is discussed.The aforementioned methods for channel estimation are simulated in Matlab environment, and the results are provided.更多还原