【作者】 王昵；

【导师】 邓平；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2008， 硕士

【摘要】 随着近几年来无线通信的迅猛发展,对下一代移动通信(4G)的研究已经开展得如火如荼。新一代移动通信可以提供更高的数据传输速率,在有限的频谱资源上实现高速率和大容量。其中,正交频分复用(OFDM)可以有效地将频率选择性衰落信道转化成多个并行平坦衰落信道,从而大大提高传输效率。多输入多输出(MIMO)在原有传输带宽和功率消耗的基础上,在发射机与接收机之间并行传输多路独立数据,大大增加信道容量,成倍地提高频谱利用效率。将OFDM和MIMO技术相结合,可以兼具OFDM抗多径时延特性、抗频率选择性衰落以及高频谱利用率,和MIMO有效提高系统容量,显著提高网络覆盖范围和传输可靠性的优点。在MIMO-OFDM系统中,通过接收端信道估计获得信道状态信息(CSI,Channel State Information),是正确恢复发送信号的必要环节,其准确性将直接影响系统整体性能。本文主要针对MIMO-OFDM系统中信道估计展开研究。第一章介绍了OFDM、MIMO的技术背景与发展现状,及信道估计技术概况。第二章介绍了无线信道的传播特性。首先介绍了无线信道传播中信号强度的影响因素,进而引出衰落信道的定义和分类。第三章介绍了OFDM、MIMO及MIMO-OFDM系统,并简要介绍了MIMO系统空时编码技术及发展情况。最后对OFDM系统中的重要参数做了说明。第四章研究SISO-OFDM系统中的信道估计技术。针对块状、梳状和散布状导频信道估计,重点研究了4种导频估计算法、6种内插算法以及导频图案对传输性能的影响。第五章研究MIMO-OFDM系统中的信道估计技术。针对频域估计,研究了导频图案设计。针对时域估计,推导了主要抽头简化算法和利用最优训练序列优化估计性能,并提出判决反馈时域重要抽头改进算法。最后,基于前面研究结果,结合WiMAX802.16e协议,完整实现了MIMO-OFDM系统中的信道估计。第六章总结了本文的工作,给出结论,对下一步工作进行了展望。更多还原

【Abstract】 With the rapidly increase of wireless data and multimedia application in recent years, research on the next generation(4G) mobile communication has being widely and deeply developed. The 4G communication system is a wireless network with high spectrum efficiency and high rate in limited bandwidth, and it supports high bit rate data transmission for many services. With the parallel modulation, orthogonal frequency-division multiplexing (OFDM) can change a frequency selective fading channel to be several flat fading channels, thus improving the transmission efficiency tremendously. Multiple-input multiple-output (MIMO) system which utilize multiple transmit/receive antennas can significantly increase the channel capacity, greatly improve the spectrum efficiency.Combination of OFDM and MIMO techniques can take advantages of the merit of both techniques, keeps the robust performance in the frequency-selective fading channel by OFDM and enhance system capacity enormously by MIMO.MIMO-OFDM technology relies on accurate channel state information (CSI) to be available at the receiver. Channel estimation is critical in the design of MIMO-OFDM systems for coherent detection and decoding. Therefore, this thesis has investigated the channel estimation techniques for MIMO-OFDM systems.In chapter 1, the background and development of OFDM and MIMO technologies are introduced, as well as the channel estimation technology profile.In chapter 2, the characteristics of mobile communication channel are discussed. Firstly the influence factors of signal strength are discussed, then the definition and classification are introduced.In chapter 3, the OFDM, MIMO and MIMO-OFDM system are introduced, besides, the introduction of space-time coding in MIMO system is presented, and the significant parameters in OFDM systems are introduced.In chapter 4, the channel estimation techniques for SISO-OFDM systems are investigated, mainly towards block-type, comb-type and spread-type pilots channel estimation, a survey of recent pilot assisted estimation algorithms is provided, including 4 pilot estimation algorithms and 6 interpolation algorithms. Besides, the influence to transmit performance by pilot-pattern is also studied.In chapter 5, the channel estimation techniques for MIMO-OFDM systems are investigated. In the frequency-domain, the design of pilot-pattern is studied with computer simulation. In the time-domain, we provide and simulate a design of main-tap algorithm to simplify the estimators, and a design of optimal training symbols to optimize channel estimation performance. Then we propose a channel estimation scheme using both two algorithms discussed above adding decision feed back technology in time-domain. Consequently, based on the research results presented above and 802.16e WiMAX standard, the complete simulation and performance evaluation of MIMO-OFDM system channel estimation techniques are provided.In last chapter, the conclusion of thesis is given, as well as the necessary future work.更多还原