【作者】 李忻；

【导师】 聂在平；

【作者基本信息】 电子科技大学 ， 信息与通信工程， 2005， 博士

【摘要】 虽然第三代移动通信(3G)技术尚待完善,新一代无线通信技术已扑面而来,其无所不在、高质量、高速率的移动多媒体传输目标让人耳目一新。然而,实现这一振奋人心的通信目标并非易事,常规单天线收发通信系统面临严峻挑战。即使采用常规发射分集或接收分集或智能天线技术已不足以解决新一代无线通信系统的大容量与高可靠性需求问题。可幸的是,多入多出(MIMO)无线通信技术提供了解决该问题的新途径,它在无线链路两端均采用多天线,分别同时接收与发射,能够充分开发空间资源,在无需增加频谱资源和发射功率的情况下,成倍地提升通信系统的容量与可靠性。然而,与常规单天线收发通信系统相比,MIMO通信系统中多天线的应用面临大量亟待研究的问题。 本文以高技术研究发展计划中的“新型天线与分集技术”项目为契机,围绕新一代无线通信中的MIMO信道建模与多天线设计这一主题,在MIMO信道建模、信号相关性分析、多天线的特性对MIMO信道性能的影响、MIMO多天线设计以及MIMO实验数据分析等方面进行了系统而深入地研究。这些研究为准确分析与设计空时编解码和调制解调提供了有力的保障,为评估衰落信号的相关特征奠定了坚实的理论基础,为MIMO多天线设计提供了重要的理论指导与全新的设计思路。 本文的研究内容与主要贡献可以分为四大层次: 第一个层次系统地分析MIMO信道中信号的相关性,研究相关性对MIMO信道性能的影响,为MIMO信道建模与天线设计奠定了坚实的理论基础,对MIMO信道容量和误码性能分析具有重要的指导作用。首先,在计及天线单元的方向性、间距和互耦等天线特性以及达波角和角度扩展等信号和环境特征下,推导出天线单元间的空间相关系数的解析通式,并进一步得出在各种达波功率角谱下相关性的解析表达;其次,推导出双分集最大比合并相关瑞利衰落的误码性能的解析表达,使评估信道相关性对分集合并性能的影响更加方便;接着,以平均差错概率的解析上界的形式定量地给出了相关性引起的V-BLAST系统的性能损失,发现收发两端的相关性可以等效归并到发送端,并得出这种性能损失的实质是降低各数据流的有效信噪比,从而得到一种系统链路设计思路:如果接收端的相关性较高,可以通过降低发射端的相关性给以一定程度的补偿。更多还原

【Abstract】 The third-generation mobile communication (3G) technologies are still expected very much to be improved, however, the new generation wireless communication technologies are emerging and booming, whose target of providing ubiquitous, high quality, and high data rate mobile multimedia transmission sounds much attractive. Of course, the implementation of this unprecedented target is not so easy, and the traditional communication systems using single-antenna transmitting and receiving are confronted with a stiff challenge to achieve this target. The demands of both high capacity and high reliability in the new generation wireless communication systems are not enough to be met even though one of the traditional improved measures, such as the traditional transmit diversity, receive diversity and smart antenna technology, is used. Fortunately, the creative technology, namely Multiple-Input Multiple-Output (MIMO), has provided a novel solution to this problem. MIMO methods make use of multiple-antenna at both the transmit and the receive side of the radio link to multiply the capacity and reliability over more traditional wireless communication systems by fully exploring the space resource within the same frequency band at no additional power expenditure. However, many more problems are emerging and urgently wanted to be solved in MIMO communication systems due to introducing the multiple-antenna comparing with the traditional single-antenna systems.This dissertation, sponsored by the project of the Novel types of antennas and diversity technology which is one part of the National High Technology Research and Development Program (863 program), focuses on the MIMO channel modeling and multiple-antenna designing for new generation wireless communication systems, and is concerned with the systematic and thorough researches on many aspects, such as MIMO channel modeling, signal correlation analysis in MIMO channel, effects of multiple-antenna on the performance of MIMO channel, the design of multiple-antenna andanalysis of MIMO experimental data. These researches provide powerful guarantee for precise analysis and design both of space-time coding/decoding and modulation/demodulation, and establish a solid theoretical basis for the correlaton evaluations of fading signals, as well as provide both important insights into MIMO antenna design and novel design ideas.The major contributions in this dissertation include four levels.The first level is mainly concerned with the systematic analysis of the signal correlation in MIMO channels. The research on the effects of signal correlation on the performance of MIMO channels establishes the solid theoretical basis both for MIMO channel modeling and MIMO antenna designing, and provide important insights into the analyses of capacity and Bit-Error-Ratio (BER) of MIMO channels. First, the general analytical expressions are obtained for the spatial correlation (SC) between antennas including the antennas properties (such as radiation patterns, antenna spacing, antenna mutual coupling (AMC)), signal and environment properties such as angles of arrival (AOAs), the angular spread (AS) of the scattering signals; the detailed analytical expressions for the SC under various power azimuth spectrum (PAS) distributions (such as uniform, cosine, Gaussian, Laplacian) are further derived. Secondly, the analytical solutions for BER performance for two-branch diversity reception and Maximal-Ratio Combining (MRC) in correlated Rayleigh fading are obtained, with which it is convenient to examine the effects of the fading correlation on the diversity performance. Thirdly, the performance loss due to correlation in V-BLAST is quantified in forms of the analytical upper bound of the average probability of error (APE), and it is found that the correlations at both ends of the wireless link can be incorporated equivalently into only those at the transmit end, which shows the losses essentially reduce the effective signal-to-noise ratio (SNR) of the data substreams. As a result, an idea is obtained for systematic design of wireless link: the high correlation at the receive end canbe compensated for to a certain degree by reducing the correlation at the transmit end.In the second level, the systematic researches on MIMO channel modeling and the effects of multiple-antenna on the performances of MIMO channel are achieved. First of all, the number of the effective scatterers in propagation environment is modeled as a birth and death process, and then a dynamic MIMO wireless channel model is proposed to investigate the effects of mobility both of scatterers and transceiver antennas on the SC and capacity of MIMO channels, and hence it remedies the deficiency in previous investigations. Next, based on the engineering practical applications and focused on the performances of multiple-antenna, the effects of many aspects such as antenna array orientation, AMC and the channel coupling (CC) between receiver passages, on the performance of MIMO channels are investigated, which establish the solid theoretical basis for the MIMO antenna design. In the research of the impact of antenna array arrangement (orientation) on the performance of MIMO wireless channels, it is obtained that the transmit and receive antenna array should be rotated to make their norm point to the mean direction of arrival (DOA) and departure (DOD) to attain higher capacity, respectively. It is found that the orientation of the array with smaller AS dominates the impact, and that increasing the AS diminishes and even eliminates the impact. In the research of the effects of AMC on the performance of MIMO wireless channels, the general coupling matrix is drived, and the analytical expressions for both the mean received power of each antenna and the SC between antennas in the presence of AMC are also provided. The effects both of the AMC and mean DOA on both the SC and capacity of MIMO channels are analyzed. Both the conditions under which AMC has no effect on the SC and under which there is no power difference are identified, respectively. It is found that under certain conditions AMC has a beneficial decorrelation effect to improve channel capacity. In the research of CC in in a two-branch antenna polarization diversity system by applying a network theory framework, the impacts of CC on both the correlation between diversity branches and the mean power difference therein are analyzed, and it is obtained that thecorrelation increases but the mean power difference may decrease due to CC, and hence it is found that under certain conditions the CC can improve diversity performance. Finally, an equivalent relation of CC is proposed, which explains CC from the point of view of antennas and states that the CC is equivalent to each antenna deviating a complex angle from its orginal position. This equivalent relation bridges CC and the deviation angles of antennas, and helps to analyzing and correcting CC.The third level is mainly concerned with the MIMO antenna design, which is the engineering implementation according to the design rules provided by the theoretical analyses. First of all, through reviewing the existing MIMO antenna design schemes and deeply analyzing the MIMO antenna design, the basic technical requirements for MIMO antennas are obtained and the properties of MIMO antennas are also summarized. The author, cooperating with others, proposes many kinds of MIMO antenna schemes, such as one scheme for basestation antennas, one for terminal antennas and one for handset antennas, and provides each design instance, which has novel design ideas and shows excellent performance. These novel types of antenna designs not only bring progress in antenna design techniques, but also advance development in MIMO communication technology.The last level focuses on the analyses of MIMO experimental data to validate the theoretical researches and to provide information both for improving MIMO channel modeling and optimizing antenna designing. A large numbers of measurement campaigns are performed using the MIMO measurement platform developed by the author and others in indoor and outdoor environments. Some experimental results are provided, i.e., the distribution of the MIMO channel coefficients, the distributions both of the eigenvalues of the channel correlation matrix and channel capacity, the SC of channels, and the BER performance of the MIMO channel transmission, etc. The experimental phenomena and results are analyzed in detail, and hence many important conclusions are obtained, which are helpful to thoroughly更多还原