基于几何的MIMO移动对移动（M2M）衰落信道建模的研究

【作者】 张梅；

【导师】 申东娅；

【作者基本信息】 云南大学 ， 通信与信息系统， 2011， 硕士

【摘要】 移动对移动通信系统(M2M:Mobile-to-Mobile communication systems)是一种不基于固定式基站的移动通信系统,目前, M2M通信由于应用性强且能较好地满足新一代无线通信的要求而受到了广泛地关注,例如,它可应用于无线移动ad hoc网络、中继蜂窝网络及智能传输系统中的短距离通信(如IEEE 802.11p标准)。而输入多输出(MIMO:multiple input multiple output)技术能通过空间分集减弱多径衰落的影响,并提高无线通信系统的频谱利用率与信道容量等。针对MIMO的技术特点,将其应用于M2M系统,从而能提高M2M系统的信道容量、系统的服务质量,并增大传输功率与带宽,降低传输的误码率,使得系统的传输性能大大提高。另外了解无线通信链路的信道特性有助于设计理想性能的通信系统,而目前已有的许多信道模型不能运用于M2M通信系统,也没有已知的信道模型可以直接来描述M2M信道的衰落和空-时-频域行为,因而,在研究M2M通信系统时,建立MIMO M2M信道模型,充分研究信道的空间特性是很有必要的。为此,本文以基于几何的MIMO M2M衰落信道建模研究为主题,结合了MATLAB仿真,在M2M衰落信道建模及其统计特性方面展开了研究,致力于建立新的M2M通信信道模型及能反映真实传播环境的信道模型,并结合MIMO技术,研究空-时-频域中MIMO M2M衰落信道的统计特性。论文的主要研究工作如下：首先,针对频率非选择性Rician MIMO M2M信道,采用基于几何散射模型的信道建模方法,并结合现有的MIMO几何模型,提出了基于中继协作通信的三环几何散射分布模型,分别推导了该模型在散射环境和视距(LOS:Line-of-Sight)情形下的时间自相关、空时互相关函数及多普勒功率谱密度,并根据推导出的新结论,对该模型的时域自相关特性以及空域互相关特性进行了仿真分析,并仿真比较了不同模型分别在不同容量公式(传统的由天线的均匀相关得到的容量公式与由改进后的指数相关而得到的容量公式)下的情形,结果表明该几何三环MIMO M2M信道模型具有较强的适用性,且能较准确反应天线间距、波达角(AOA)、波离角(AOD)等因素对MIMO M2M信道相关性的影响。其次,考虑散射体分布的成簇性,将上述模型扩展到频率选择性衰落信道。该宽带模型不仅考虑了收发两端的移动及频率选择性MIMO M2M衰落信道收发两端存在的视距分量,而且还考虑了频率对信道的影响,推导出了宽带MIMOM2M信道的空时频互相关函数、功率迟延谱及多普勒功率谱密度,探讨了各因素(包括有天线间距、AOA、AOD、扩展因子、移动速度等)对信道相关性及信道容量的影响,并对其进行了仿真与分析。最后,运用实测数据对前面所提出的基于几何三环的MIMO M2M衰落信道模型进行了验证,结果表明,该几何三环信道模型的仿真结果与实测结果得到了较好的吻合。更多还原

【Abstract】 Mobile-to-Mobile (M2M) communication system is a kind of mobile communication system which is not depending on the fixed base station. Recently, M2M communications have received much attention due to its good performance and several emerging applications, such as wireless mobile ad hoc networks, relay-based cellular networks, and dedicated short range communications (DSRC) for intelligent transportation systems (e.g., IEEE 802.11p standard). And the MIMO technology can overcome the fading effect effectively, and to provide higher capacity and higher spectrum efficiency through the space diversity.The M2M systems using MIMO technology, which can improve the MIMO M2M channel capacity, system quality of service, increase the transmission power and bandwidth, reduce the bit error rate, and improve the M2M system performance greatly. Furthermore, understanding the characteristics of the MIMO M2M channel contribute to design the communication systems with ideal performace. However, the exist channel model could not be used to describe the propagation properties of the M2M fading channels, meanwhile, there are not sufficient research results could be used to explain the space-time-frequency characteristics of M2M channels. So, the MIMO M2M channel modeling and a good understanding of the space properties of MIMO M2M channel for studying M2M communication systems is very necessary.So, we focus on the research of MIMO M2M fading channel modeling, by utilizing the computer simulations method, modeling the M2M channel model and analyzing the statistical properties of the channel, in order to build new MIMO M2M channel model for real wireless propagation environment and study the space-time-frequency statistical characteristics for fading channel combining with the MIMO technology. The focus of this paper is MIMO M2M channel modeling, including as follows:Firstly, for the frequency non-selective Rician fading MIMO M2M channel, we provide a geometrical triple-ring scatters distribution model based on relay cooperative communications. In this channel model, we use the method of channel modeling based on geometrical scatters model, and combined with existing channel model. Then, we derived the auto-correlation function, the space-time cross-correlation function and the Doppler Power Spectral Density of the scatters component and the LOS component respectively, and also give an analysis and simulation to the auto-correlation function in time domain, the cross-correlation function in space domain,and then the capacities of various channel models obtained by different capacity expression (e.g. the formula derived from traditional uniform-correlation antenna matrix and the modified exponent-correlation antenna matrix) are simulated and compared. By comparison, the simulation results show that the geometrical triple-ring MIMO M2M channel model has strong applicability, and can reflects that the spacing of the antennas, the angle-of-arrival, the angle-of-departure and other factors how to affect the correlation of the MIMO M2M channel model.Secondly, the model is extended to the frequency-selective fading channel by considering the clusters of the scatterers. And, this wideband channel model not only takes into account both transmitter’s and receiver’s mobiling and the LOS component exsiting in frequency selective Rician MIMO M2M channel, but also consider that the frequency how to affect the channel’s correlations. And then, the space-time-frequency Cross-Correlation function, the Power Delay Profile and the Doppler Power Spectral Density of the wideband MIMO M2M channel model are derived. Meanwhile, we discuss that the various factors including the spacing of the antennas, AOA, AOD, spread factor, the velocity of moving and so on how to affect the correlation between the channel and the channel capacity, then, some simulations and analysis are obtained.Finally, the proposed geometric triple-ring model of MIMO M2M fading channel is validated by using the measured data. And, the results show that the proposed channel models with the experimental results are in good agreement.更多还原