【作者】 金颖妮；

【导师】 郑正奇；

【作者基本信息】 华东师范大学 ， 无线电物理， 2010， 博士

【摘要】 第三代合作伙伴计划(3GPP)是第三代移动通信(3G)以及后三代移动通信(B3G)技术标准最具影响力的制定者,近几年来,宽带码分多址(WCDMA)、时分同步码分多址(TD-SCDMA)、高速数据包接入(HSPA)等各种系统已经逐步在全球大规模部署,同时,3GPP又启动了长期演进(LTE)、HSPA+、LTE-Advanced等项目。LTE系统采用多输入多输出(MIMO)和正交频分复用(OFDM)作为两大主要技术以应对系统大容量与高频谱利用率等需求。MIMO在通信链路两端均采用多天线系统,同时发射接收信号,充分利用系统空间资源,在无需增加发射功率和频谱资源的情况下,提高系统性能。在当今无线通信技术发展中扮演越来越重要的角色,MIMO相关技术如信号处理、编解码、调制解调以及资源管理等研究一直处于前沿领域,然而,MIMO系统仍有很多亟待研究的问题。本文是基于3GPP LTE系统架构的MIMO技术研究,主要内容包括以下几个方面:第一.系统的研究MIMO信道中信号的空间相关性及其对MIMO系统性能的影响,为基于3GPP LTE的MIMO信道建模奠定理论基础,为信道容量以及MIMO其他技术的研究提供参考依据。首先,在考虑四天线结构、互耦因素、典型功率角谱分布(PAS)、天线间距等系统特征参数的情况下,推导接收端信号的相关系数,并对其进行数值分析,指出MIMO系统典型参数与相关系数的关联,弥补了现有研究的不足;其次,在评估信号空间相关系数的基础上,基于Kronecker模型解释信号相关性和信道相关性的区别联系,并利用Kronecker理论推导信道相关矩阵模型;最后,结合MIMO系统研究的重点,分析相关性对MIMO系统性能起重要作用的根本原因。第二.系统的研究MIMO无线信道建模。指出传统单入单出(SISO)信道建模与MIMO信道建模的本质区别,以及MIMO信道建模理论研究的关键;其次,基于MIMO信道建模方法分析目前较典型的MIMO信道模型,提出MIMO信道模型准确性仿真验证方法;再次,基于3GPP 25.996协议,用射线跟踪建模法和相关矩阵建模法分别对MIMO信道建模,即基于射线跟踪理论推导出MIMO信道在空间分集、极化分集、混合分集以及直达径(LOS)场景下的信道传输函数解析式,然后,在此结论基础上,用相关矩阵法推导出MIMO信道空间相关矩阵、极化相关矩阵以及时间相关矩阵的形式;最后,推导并数值分析空间、时间相关性对信道容量的影响,以及提出两种方法建立的MIMO信道模型的准确性仿真验证流程。第三.系统的研究MIMO信道测量与估计。主要对象:功率时延谱(PDP)、PDP漂移、多普勒功率谱(DPSD)、多普勒频移、波束成形(BF)、多径径数、相干带宽、相干时间、多径衰落相关性、接收信号总功率衰落以及典型天线结构下信道冲激响应(CIRs)的相关性等。首先是原理部分,1.介绍如何得到CIRs以及PDP,提出如何通过它们推导出信道其他参数。2.提出一种简单有效的方法估计最大多普勒频移,分析实际系统中影响估计准确性的因素并提出算法修正,并验证。3.提出在有限反馈信道状态信息(CSI)时的BF算法纠正方案、验证以及算法评估;其次,针对以上原理,根据3GPP LTE协议配置参数,进行测量实验,通过对实验数据提取CIRs、PDP以及其他信道传播特性参数,分析结果,并验证相关结论。最后对整个LTE样机系统的软件结构进行介绍,并例举其在仿真平台Linkstar上的实现。更多还原

【Abstract】 3GPP is the most influential establisher of technical reports and technical specifications of 3G and B3G In recent years, kinds of systems like WCDMA, TD-SCDMA, and HSPA have been widely deploying all over the world, in addition, 3GPP initiated some new projects of long time evolutions including LTE, HSPA+, and LTE-Advanced.LTE system adopts MIMO and OFDM as its two most important fundamental techniques, so as to respond to the requirements of large capacity and high spectral efficiency. MIMO system adopts multi-antenna systems on both sides of sender and receiver, sending and receiving signals at the same time, fully making use of space resources, improving system performance without extra transmitting power and spectrum resource. MIMO more and more play an important role in the current development of wireless communications. Some relevant techniques of MIMO like signal processing, encoding/decoding, modulation/demodulation, and resource management are at the forefront of research and design of mobile communications. However, there are still many remaining problems of MIMO system are urgently wanted to be studied and solved. This dissertation mainly discusses the MIMO theories which are based on the framework of 3GPP LTE system, some new strategies are presented as follows:1. This part is mainly concerned with the systematic analysis of the signal correlations in MIMO channels, this analysis of signal correlations for the MIMO systems establishes solid theoretical basis for MIMO channel modeling, channel capacity, and so on. Firstly, providing four-antennas on receiver, mutual coupling, four kinds of classical PAS, and antenna spacing which characterise the MIMO systems, mathematically deducing and analyzing the expressions of signal correlations on receivers, so that explaining the relationships of correlations and parameters of MIMO systems; Secondly, explaining the differences between signal correlation and channel correlation based on the above-mentioned expressions and the Kronecker model, then analyzing the channel correlation by Kronecker theories; Thirdly, combining with some key techniques of MIMO, analyzing the root causes of the important role which the correlation plays in the performance of MIMO systems. 2. This part is mainly concerned with the MIMO wireless channel modelling. Firstly, discussing fundamental differences between traditional SISO channel modelling and MIMO channel modelling, the key methods of MIMO channel modelling theory; Secondly, analyzing some current classical MIMO channel models with basic modeling methods, and offers the validation procedures of simulation of MIMO channel models; Thirdly, based on the above-mentioned discussion, separately making use of ray-tracing and correlation matrix to model the MIMO channel based on the 3GPP 25.996 technical report, that is, expressions of channel transfer function of spatial diversity, polarization diversity, hybrid diversity and LOS situation are derived respectively by ray-tracing, based on the results, the expressions of spatial correlation matrix, polarization correlation matrix and time correlation matrix are derived; Finally, deducing and mathematically analyzing the impacts on the channel capacity from channel spatial correlation and time correlation, then offering the validation procedure of simulation of MIMO channel models which established by two the above methods respectively.3. This part is mainly concerned with the measurements and estimations of MIMO channel. The emphasis are: PDP, PDP shifts, DPSD, Doppler spread, BF, multi-path number, coherence bandwidth, coherence time, correlation of multi-path fading, power fading of the receiving signals, and correlation of CIRs of given antenna architectures, etc. Firstly, principles can be divided into three parts: l).How to get CIRs, PDP, by which other parameters can be obtained. 2). Proposing a simple and effect plan for estimating the Maximum Doppler spread, discussing the practical factors which influence the accuracy of the estimation of Doppler spread, validating the conclusions by simulation. 3). Proposing an improved plan and assessment ways for the BF algorithm under a limited CSI feedback MIMO system; Secondly, configuring communication scenarios based on above-mentioned principles and 3GPP LTE specifications, obtaining and analyzing the CIRs, PDP, and other channel parameters, so as to draw some conclusions about MIMO channel and propagation. Finally, introducing the whole framework of LTE prototyple’s software system, and exemplifying its implementation on a simulation platform named Linkstar.更多还原