室内MIMO无线信道模型和信道容量研究

本文从工程的实际出发,首先提出一种修正的室内MIMO无线信道模型,该模型有效地修正先前室内MIMO无线信道模型的不足,具有明显吻合室内实际通信环境的特点,然后分析天线方向性以及天线单元间的互耦对室内MIMO无线信道容量的影响.数值模拟验证了这种影响,并得到在一定条件下互耦导致的天线方向图畸变产生角度分集,提高信道容量,互耦对空域相关性无影响的条件以及室内丰富的多径使天线方向性对信道容量的影响不明显等结论.最后,实验也证实理论分析.     

基于空时相关性的MIMO无线信道建模及仿真

针对多输入多输出无线信道的空时相关性，文章提出了一种改进的MIMO无线信道模型。该模型利用改进的Jakes模型仿真器来产生独立同分布零均值的复高斯随机变量，从而保证各个传播路径间的相关性很小。仿真结果表明改进的MIMO无线信道模型能够准确的描述出空时相关的MIMO无线信道的统计特性，即空间相关性随天线单元间距增大而战小，随散射信号角度扩展增大不是一致减小．     

频率选择性衰落环境中MIMO系统信道容量研究

提出了一种频率选择性环境中多输入多输出系统信道容量的分析方法.该方法基于接收均匀圆阵构建了蕴含天线间距、散射角大小和多径数等模型物理参数的衰落空间相关模型。分析了MIMO OFDM系统信道衰落的统计特性。在此基础上利用Wishart分布的性质详细推导了任意天线数的MIMO OFDM系统的信道容量及其上下限。该方法回避了已有方法需要求取信道衰落相关特征值概率密度函数的问题，降低了运算量；并且可以有效地分析在频率选择性环境中模型物理参数对信道容量的影响。仿真结果表明，随着天线间距的增大，系统的平均信道容量也逐渐增大；但当天线间距增大到一定程度后,信道容量变化不明显，散射角越大，信道容量的增长速率越快，当接收信噪比较高时,平均信道容量的上下限接近于其实际值。     

基于FDTD方法的无线信道衰落特性模拟研究

为了表述无线信道衰落的时变及远区分布特性，提出了利用时域有限差分(FDTD)方法研究由多径效应引起的时变无线信道衰落的方法。在此将无线信道的衰落建模为随机过程，而不是通常的确定性随机变量。首先基于Clarke统计模型，利用FDTD方法研究了时变无线信道的小尺度平坦衰落特征；然后利用Monte Carlo方法和FDTD方法产生了具有信道多普勒功率谱特性的色高斯随机过程，再基于无线信道的时变统计特性建模，用Suzuki模型研究了时变无线信道的快衰落；最后将无线信道衰落特性分布和理论分布做了比较，验证了方法的有效性。     

Measurement and Statistical Analysis of the Temporal Variations of a Fixed Wireless Link at 3.5 GHz

This paper presents the measurement and statistical analysis of the temporal variations of the radio channel defined by a fixed link at 3.5 GHz in suburban areas. The analysis provides the required information about the temporal stability of the channel, the probability of occurrence and depth of fades, the Doppler spectrum and, in general, the influence of the environment on the signal behaviour. In particular, the effect of fast traffic on a motorway in the neighbourhood of the receiver is investigated, obtaining some general conclusions particularly useful in wireless communication systems design. Rafael P. Torres was born in M′laga, Spain, in 1961. He received his MS degree in Physics from the University of Granada (Spain) in 1986 and his Ph.D. from the Telecommunications Engineering School at the Polytechnic University of Madrid (UPM) in 1990. From 1986 to 1990 he was with the Radio Communication and Signal Processing Department of the UPM as a research assistant. During this time, he worked about numerical methods in electromagnetics, and its applications to design of passive microwave devices like radomes, circular polarizer, rotators and planar lenses. He became an associate professor in the Department of Communication Engineering of the University of Cantabria (Spain) in 1990. From this time to the present, he has participated in several projects about RCS computation, on board antennas analysis, electromagnetic compatibility, and radio-propagation. He is co-author of a book about the CG-FFT method, author of several chapters in different books, more than 20 papers, and about 80 conference contributions. He has been the leader of the group that have developed the code CINDOOR, Computer Tool for Planning and Design of Wireless Systems in Enclosed Spaces. His current research interests include radio-propagation for wireless and mobile communications, as well as the simulation and design of new wireless communications systems. Beatriz Cobo was born in Santander, Cantabria (Spain), in October 1974. She received the M.Sc. degree in telecommunications engineering from the University of Cantabria, Spain, in 2000. During the period 2000-2004 she developed her research work in the Department of Communications Engineering in the Higher Technical School of Industrial Engineering and Telecommunications at the University of Cantabria. During the first two years she was an assistant researcher of the FEDER project “Subsystems of Radar and Radiocommunications in Maritime Traffic Services” and the last two years she worked in the project “Systems and Applications WLAN and WPAN”. At the moment she is a Ph.D. student at University of Cantabria and from October 2004 she is an assistant professor at University of Oviedo. Her areas of research include high-frequency methods, applied to the characterization of the natural scenarios where a radar can be located. Dimas Mavares received B.S. degrees in electronic engineering from la Universidad Politécnica Antonio José de Sucre, Venezuela, in 1994, and M.S. degree in electronic engineering form la Universidad Simón Bolivar, Venezuela, in 1997. From 1997 to 2001 he worked as an instructor in la Universidad Politécnica Antonio José de Sucre. Since 2002 he has been pursuing a Ph.D. degree in Communications Engineering from the Universidad de Cantabria, Spain. His research interests include MIMO wireless communications, channel estimation, space-time coding and neural networks. Francisco Medina was born in Santander, Cantabria (Spain), in July 1974. He received the M.Sc. degree in telecommunications engineering from the University of Cantabria, Spain, in 2002. During three months in 2002 he hold a scholarship to stay at Bordeaux (France) and to work in the company Thalès Systèmes Aéroportés. Nowadays he works as a sales engineer at the Export Department of Nexans in Malia?o, Cantabria (Spain), an expert company in cables and cabling systems. Susana Loredo was born in Gijóon, Spain, in 1972. She received the M.S. and Ph.D degrees in telecommunications engineering from the University of Cantabria, Spain, in 1997 and 2001 respectively. From 1998 to 2001 she was with the Department of Communications Engineering as a Research Assistant. During this time, she worked on numerical and high frequency methods applied to the characterization of the radio-propagation channel, and also on the narrowband and wideband experimental characterization of the indoor radio channel. In 2001 she joined the Department of Electrical Engineering at University of Oviedo, Spain, as a Research Scientific. From this time to the present, she has been working on MIMO channel characterization using high frequency approaches and source reconstruction methods to characterize the antenna radiation.     

Simulation Models for Investigation of Multiuser Scheduling in MIMO Broadcast Channels

Spatial correlation is a result of insufficient antenna spacing among multiple antenna elements, while temporal correlation is caused by Doppler spread. This paper compares the effect of spatial and temporal correlation in order to investigate the performance of multiuser scheduling algorithms in multiple‐input multiple‐output (MIMO) broadcast channels. This comparison includes the effect on the ergodic capacity, on fairness among users, and on the sum‐rate capacity of a multiuser scheduling algorithm utilizing statistical channel state information in spatio‐temporally correlated MIMO broadcast channels. Numerical results demonstrate that temporal correlation is more meaningful than spatial correlation in view of the multiuser scheduling algorithm in MIMO broadcast channels. Indeed, the multiuser scheduling algorithm can reduce the effect of the Doppler spread if it exploits the information of temporal correlation appropriately. However, the effect of spatial correlation can be minimized if the antenna spacing is sufficient in rich scattering MIMO channels regardless of the multiuser scheduling algorithm used.