MB-OFDM系统的信道估计算法改进与仿真

发布时间：2018-11-19 14:57

【摘要】：超宽带(UWB)技术是一种现今的新兴技术,特别适用于短距离和低功耗无线通信系统,其应用与研究也在这几年更被重视。其中作为以短距离低功耗为显著特点的IEEE 802.15.3a无线个域网协议,在智能家居,智能建筑,智能交通以及医院监护等前沿领域有着良好的应用前景。UWB技术有多带正交频分复用超宽带(MB-OFDM-UWB)和直扩码分多址超宽带(DS-CDMA-UWB)两种方案组成,本文的研究是基于MB-OFDM-UWB系统进行阐述。MB-OFDM系统的关键部分在于是否能够得到更高的数据传送速率和频谱利用率,而且一般都是采用相干检测。在这个过程中,首先需要有更为实时并且准确的信道信息,而信道信息是来自于信道估计的结果的预测,因此整个通信系统的性能很大程度上是取决于信道估计的精度,信道估计算法的优化就成为MB-OFDM系统接收端着重研究的一部分,这也是通信系统里不可或缺的研究部分。优越的信道估计算法可以获得信道频域响应的改变,通过一系列的处理,来得到准确的信道信息。本文讨论的前提是有良好的同步及均衡技术,故重点是信道估计算法的改良过程。第二章首先介绍了UWB信道模型的一些主要特征,再介绍OFDM技术的基本原理。第三章主要介绍MB-OFDM的改良信道估计技术,这一技术是基于导频信道估计算法的改进,文中分析了两种常用的信道估计算法,分别是最小二乘(LS)信道估计算法和最小均方误差(MMSE)信道估计算法。由于算法复杂度的影响,最终选取了较为简单的LS信道估计算法。未经过处理的结果中仍然存在噪声信号,严重影响了信道估计的准确度。源于这一点的影响,在信道估计算法中引入小波降噪进行处理,提出了本文MB-OFDM的改良信道估计算法。整个过程首先是利用LS信道估计算法得到已知导频位置的信道频域响应,采用较为简单的Haar小波进行小波降噪,最终分别采用线性插值、高斯插值、DFT插值得到比对结果,采用插值算法是为了能获得整个信道的频域信道响应。第四章主要的内容是对MB-OFDM-UWB系统的仿真,给出了改良之后的误码率与信噪比的仿真图,同时分析了各种算法的不同点。而通过理论分析和观察仿真结果图形可表明本文提出的改良信道估计算法在一定程度上性能改善较大,能够提高整个通信系统的性能。
[Abstract]:Ultra-wideband (UWB) technology is a new technology, especially for short-range and low-power wireless communication systems. Its application and research have been paid more attention in recent years. Among them, IEEE 802.15.3a wireless personal area network protocol, which is characterized by short distance and low power consumption, is used in smart home, intelligent building, Intelligent Transportation and Hospital Surveillance have good application prospects. UWB technology consists of two schemes: Multiband orthogonal Frequency Division Multiplexing (MB-OFDM-UWB) and Direct spread Spectrum Code Division multiple access (DS-CDMA-UWB). The research of this paper is based on MB-OFDM-UWB system. The key part of MB-OFDM system is whether to get higher data transfer rate and spectrum efficiency, and generally uses coherent detection. In this process, more real-time and accurate channel information is needed, and the channel information is derived from the prediction of the result of channel estimation, so the performance of the whole communication system depends largely on the accuracy of the channel estimation. The optimization of channel estimation algorithm is an important part of the research on the receiver of MB-OFDM system, which is also an indispensable part of the communication system. The superior channel estimation algorithm can obtain the channel frequency domain response change, through a series of processing, to obtain accurate channel information. The premise of this paper is that there are good synchronization and equalization techniques, so the emphasis is on the improvement of channel estimation algorithm. In the second chapter, some main characteristics of UWB channel model are introduced, and then the basic principle of OFDM technology is introduced. The third chapter mainly introduces the improved channel estimation technology of MB-OFDM, which is based on the improvement of pilot channel estimation algorithm. In this paper, two common channel estimation algorithms are analyzed. They are least square (LS) channel estimation algorithm and least mean square error (MMSE) channel estimation algorithm. Because of the complexity of the algorithm, a simple LS channel estimation algorithm is selected. Noise signals still exist in the unprocessed results, which seriously affect the accuracy of channel estimation. Because of this effect, wavelet denoising is introduced into the channel estimation algorithm, and an improved channel estimation algorithm based on MB-OFDM is proposed in this paper. The whole process is to use the LS channel estimation algorithm to get the channel frequency domain response of known pilot position, and adopt simple Haar wavelet to reduce the noise. Finally, linear interpolation, Gao Si interpolation and DFT interpolation are used to get the comparison results. The interpolation algorithm is used to obtain the frequency domain channel response of the whole channel. The fourth chapter is mainly about the simulation of MB-OFDM-UWB system. The improved simulation diagram of bit error rate and signal-to-noise ratio is given, and the differences of various algorithms are analyzed. The theoretical analysis and simulation results show that the improved channel estimation algorithm proposed in this paper can improve the performance of the whole communication system to a certain extent.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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