高铁环境下MIMO-OFDM系统的载波间干扰消除算法研究

发布时间：2019-04-21 07:52

【摘要】：随着我国高速铁路建设的快速发展与现代通信技术的与时俱进,对高速铁路下的宽带接入技术也提出了新的挑战。2010年中国铁路在第七届世界高速铁路大会上提出了自主研发时分双工的LTE-R铁路宽带移动通信系统,该系统基于的正交频分复用(OFDM)技术,具有频谱利用率高和抗多径干扰能力强等突出优点,能满足高传输速率的要求。因此,研究高速铁路环境下的OFDM通信技术具有重大意义。然而,OFDM系统中要求其载波间保持严格的正交性,在移动环境下,尤其是在超高速移动环境下,由于快速移动产生的多普勒频偏,将破坏载波间的正交性,从而引起载波间干扰(ICI),导致通信性能急剧下降。为此,解决高速铁路环境下OFDM系统中的ICI问题成为近年来研究的热点。首先,简单概述了传统的信道模型和表征高速铁路环境的信道模型,并给出对应的MIMO-OFDM系统模型,推得具体的ICI表达式,由此引出本文要研究的主要问题是分析和消除ICI。其次,通过分析研究表征高速铁路的信道模型和ICI表达式,得出信道的时变性是发生ICI的根本原因,进一步分析可知影响ICI大小的因素有莱斯K因子、信道多径数和多普勒频偏。载波干扰比作为衡量ICI严重程度的标准,定量分析了载波干扰比分别受莱斯K因子、信道多径数和多普勒频偏的影响程度,并仿真分析了实际中,车速变化时对期望信号功率和ICI功率的影响。最后,提出了两种ICI消除算法:1、循环前缀与迫零均衡联合消除法;2、自适应相位旋转共轭消除法。其中,循环前缀与迫零均衡联合消除法,是利用循环前缀实现ICI的自消除,有效的提高载波干扰比,通过迫零均衡技术检测得到发送的数据。自适应相位旋转共轭消除法,是采取两路传输技术,对发射信号采取共轭发送,对接收信号采取共轭接收并附加一组旋转相位的处理方式,通过调整旋转相位实现接收端载波干扰比最大化。再采用每两个符号周期更新一次旋转相位的机制实现自适应接收。本文三方面工作,完整的研究了引起ICI的原因,影响ICI大小的因素和有效消除ICI的方法,为以后铁路通信技术的快速提供了强有力的理论基础和技术支撑。
[Abstract]:With the rapid development of China's high-speed railway construction and the development of modern communication technology, In 2010, China Railway proposed a time division duplex LTE-R railway broadband mobile communication system at the Seventh World High Speed Railway Congress. The orthogonal Frequency Division Multiplexing (OFDM) technology based on this system has many outstanding advantages, such as high spectrum efficiency and strong anti-multipath interference ability, and can meet the requirements of high transmission rate. Therefore, it is of great significance to study the OFDM communication technology in high-speed railway environment. However, OFDM system requires strict orthogonality between carriers. In mobile environment, especially in ultra-high speed mobile environment, the Doppler frequency offset caused by fast moving will destroy the orthogonality between carriers. As a result, inter-carrier interference (ICI) (ICI), leads to a sharp decline in communication performance. Therefore, solving the problem of ICI in OFDM system under high-speed railway environment has become a hot topic in recent years. Firstly, the traditional channel model and the channel model which represent the environment of high-speed railway are briefly summarized, and the corresponding MIMO-OFDM system model is given, and the concrete ICI expression is derived. The main problem of this paper is to analyze and eliminate the ICI.. Secondly, by analyzing and studying the channel model and ICI expression of the high-speed railway, it is concluded that the time-variability of the channel is the fundamental reason for the occurrence of ICI, and further analysis shows that the factors affecting the size of ICI are Rice K factor. Channel multipath number and Doppler frequency offset. As a standard to measure the severity of ICI, the influence of Les K factor, channel multipath and Doppler frequency offset on carrier interference ratio is quantitatively analyzed, and the simulation results show that the carrier interference ratio is affected by Les K factor, channel multipath number and Doppler frequency offset, respectively. The influence of speed change on expected signal power and ICI power. Finally, two ICI elimination algorithms are proposed: 1, the combined elimination of cyclic prefix and zero-forcing equalization, and 2, adaptive phase rotation conjugate elimination. Among them, the combined elimination of cyclic prefix and zero-forcing equalization is to use cyclic prefix to realize the self-cancellation of ICI, to improve the carrier interference ratio effectively, and to detect the transmitted data by zero-forcing equalization technique. The adaptive phase rotation conjugation elimination method is a two-way transmission technique, which adopts conjugate transmission to transmit signals, conjugate reception to received signals and append a set of rotating phases to the received signals. The receiver carrier interference ratio is maximized by adjusting the rotation phase. The self-adaptive reception is realized by updating the rotation phase once every two symbol periods. In this paper, the causes of ICI, the factors affecting the size of ICI and the effective methods to eliminate ICI are studied in three aspects, which provides a strong theoretical basis and technical support for the rapid development of railway communication technology in the future.
【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN919.3

【相似文献】