共查询到19条相似文献,搜索用时 171 毫秒
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最近的研究表明,多输入多输出(MIMO)技术在不增加功率和带宽消耗的情况下具有大幅提高无线通信速率的潜力.在传统的MIMO系统(称为天线信道MIMO系统)中,多个接收天线的输出被直接选作多输出信号.提出了波束信道MIMO系统的结构.在波束信道MIMO系统中,多个波束的输出被选作多输出信号.基于阵列方向响应矢量,提出了窄带MIMO信道冲激响应矩阵的仿真算法.基于提出的信道冲激响应矩阵算法,给出了天线信道MIMO系统和波束信道MIMO系统容量极限的分析算法.理论分析和仿真结果都表明:波束信道能够提高信噪比(SNR),降低信道间的互相关性,因此波束信道MIMO系统比天线信道MIMO系统具有更大的容量极限. 相似文献
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天线互耦对MIMO无线信道性能的影响 总被引:7,自引:4,他引:3
基于多天线系统等效网络模型,导出通用耦合系数矩阵,进一步推导天线单元平均接收功率以及空域相关系数的解析式,分析互耦对平均接收功率以及互耦与平均到达角对MIMO无线信道空域相关性及其容量的影响,并给出互耦无影响与天线单元功率平衡以及互耦解相关的条件,最后给出一些数值结果以指导MIMO多天线设计. 相似文献
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根据GSM系统的实际应用,对多波束智能天线在现有GSM移动通信系统中的性能改善及其融合方案进行了研究论证,建立了多波束智能天线GSM系统融合方案模型,为多波束智能天线与现有移动通信系统的融合奠定了基础。 相似文献
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在相控阵雷达系统中采用子阵同时多波束的方式可以既不损失天线增益同时又可以扩大天线空域覆盖范围。但是如果将每个子阵看成一个天线单元则单元之间的间距会大于半波长,这样会因为栅瓣原因抬高副瓣电平,影响系统效能。提出采用频率分集的方式不仅可以避免不需要的旁瓣电平同时保证空域的覆盖。 相似文献
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张杰 《中国电子科学研究院学报》2012,7(5):506-509
MIMO(Multiple-input Multiple-output)雷达系统的单元或子阵辐射互不相同的波形,提供了足够的自由度用于天线波束的灵活成形和捷变,可以作为常规相控阵和正交雷达信号MIMO体制的通用化推广。在研究分析具有任意互相关特性的信号集合的选择综合波束方向图的基础上,采用全局遗传模拟退火算法对MIMO雷达的波束综合问题进行了最优化搜索,仿真结果显示,该算法获得了较好的结果。 相似文献
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In this paper, a novel multiple antenna system framework, which combines smart antennas (SA) with multiple-input-multiple-output (MIMO) at the transmitter, is proposed. The downlink capacity of the single-user SA-MIMO wireless systems is investigated. The joint optimization problem corresponding to the capacity is deduced. After that, upper bounds of the capacity are given in general case and in the case of equal power allocation, respectively. Furthermore, in the case of equal power allocation and the same direction of departure from one transmit smart antenna to all antenna arrays at the receiver the closed-form expression of the capacity is obtained. Some numerical results are given to show that smart antennas can bring significant capacity gain for the MIMO systems due to the smart antennas gain, without additional spatial degrees of freedom, especially at high SNR with strong correlation among the MIMO channel links or at low SNR. 相似文献
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Dynamics of spatial correlation and implications on MIMO systems 总被引:3,自引:0,他引:3
The use of multiple antennas has found various applications in the area of wireless communications. One such application has recently become very popular and is referred to as the multiple-input multiple-output (MIMO) antenna system. The main idea behind MIMO is to establish independent parallel channels between multiple transmit and receive antennas. Each channel uses the same frequency, and the transmissions occur simultaneously. In such a configuration, the amount of data transmitted increases linearly with the number of parallel channels, which is what makes MIMO so popular in the wireless world. The enormous capacity offered by MIMO systems is not realizable when the parallel channels are highly correlated. The goal of this article is to highlight the correlation concept and its impact on MIMO systems. Although correlation can be defined in many dimensions, here we focus on spatial correlation, and specifically consider antenna correlations in mobile units. We provide an overview of spatial correlation and present its underlying parameters in detail. Special attention is given to mutual coupling since it has signal decorrelation and antenna gain reduction effects. We then present how correlation in a MIMO system affects the amount of data that can be transmitted (MIMO capacity) and briefly review how power should be distributed with the knowledge of correlation. Analyses indicate that in real propagation environments, the high capacity gain of MIMO systems can be realized with improved antenna selection algorithms and power allocation strategies. 相似文献
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在大规模多输入多输出系统中,针对密集部署的大型天线阵列之间的强相关性会抑制天线选择增益效果的问题。在系统下行链路场景下建立空间相关信道模型,提出了基于天线分组的天线选择算法。根据瞬时信道相关矩阵将天线阵列划分为若干组,保证各组内天线之间相关性较强。在完成天线分组的基础上,基于信道矩阵列范数准则在各组发射天线与接收天线之间构成的子信道矩阵中选择天线,进而构造有效发射天线与接收天线之间的信道矩阵。仿真分析了所提天线选择算法对系统遍历和速率的影响,结果表明,在基站天线数为32、接收天线数为2、选择天线数为2、天线相关因子为0.9的假设下,当信噪比为10 dB时,与基于相邻天线分组的天线选择算法相比,所提算法使系统和速率约提高了27.5%,且所提算法若要与最优天线选择算法达到相同的和速率,仅需将其信噪比提升1~2 dB即可。 相似文献
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On the Diversity Order of Spatial Multiplexing Systems With Transmit Antenna Selection: A Geometrical Approach 总被引:3,自引:0,他引:3
Zhang H. Dai H. Zhou Q. Hughes B. L. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(12):5297-5311
In recent years, the remarkable ability of multiple-input-multiple-output (MIMO) wireless communication systems to provide spatial diversity or multiplexing gains has been clearly demonstrated. For MIMO diversity schemes, it is well known that antenna selection methods that optimize the postprocessing signal-to-noise ratio (SNR) can preserve the diversity order of the original full-size MIMO system. On the other hand, the diversity order achieved by antenna selection in spatial multiplexing systems, especially those exploiting practical coding and decoding schemes, has not thus far been rigorously analyzed. In this paper, a geometrical framework is proposed to theoretically analyze the diversity order achieved by transmit antenna selection for separately encoded spatial multiplexing systems with linear and decision-feedback receivers. When two antennas are selected from the transmitter, the exact achievable diversity order is rigorously derived, which previously only appears as conjectures based on numerical results in the literature. If more than two antennas are selected, we give lower and upper bounds on the achievable diversity order. Furthermore, the same geometrical approach is used to evaluate the diversity-multiplexing tradeoff in spatial multiplexing systems with transmit antenna selection 相似文献
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In this article the use of smart antennas in mobile ad hoc and mesh networks is discussed. We first give a brief overview of smart antenna techniques and describe the issues that arise when applying these techniques in ad hoc networks. We consider ad hoc/mesh networks with directional antennas, beamforming/adaptive antennas, and/or multiple-input-multiple-output (MIMO) techniques. We then show how the MAC/routing techniques can be modified to get the maximum benefit with smart antennas, while also showing examples of degradation in system performance, rather than improvement, when smart antenna techniques are added to networks with standard MAC/routing techniques. 相似文献
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This paper presents the relationship between antenna structures and the performance of two kinds of compact MIMO antennas in order to find critical factors that affect the capacity of MIMO systems. The relationship between the channel capacity and some factors (antenna efficiency, mutual coupling, correlation) are analyzed based on experimental data under indoor Rayleigh fading environment. Antenna elements mounted in two different configurations (common and separated ground plane) with antenna spacing varying, were investigated at the frequency of 2.6 GHz band experimentally. The good characteristics in the case of separated ground plane show that the proposed antennas, even with small spacing, can still achieve high capacity to combat multipath fading and deliver higher data rates. It demonstrates that multiple antennas could be mounted onto small terminal devices without much loss of capacity. It is also found that mutual coupling has positive impact which could reduce channel correlation; negative effect which could degrade antenna efficiency. In the indoor multipath-rich environment, the negative effect is dominant. 相似文献
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In this paper, we investigate the Multiple-Input Multiple-Output (MIMO) channel capacity in indoor Ricean channels based on MIMO channel measurements at 2.45 GHz. The measured data is analysed using a super resolution parameter estimation algorithm. Our results demonstrate that the line-of-sight (LOS) component in a Ricean scenario influences indoor MIMO performance through increased spatial correlation between array elements. We found that indoor channels with higher values of Ricean K factor have smaller numbers of effective multipath components and increased spatial correlation. Measurement results also showed that, the effect of varying antenna height on indoor MIMO capacity is also due to the spatial correlation of multipath propagation and has a close relationship with the separation between the transmitter and receiver.
Zhongwei Tang is currently with the Wireless Technologies Laboratory at CSIRO. He was with Microwave and Wireless Technology Research Laboratory (MWTRL), Information and Communication Group, Faculty of Engineering of the University of Technology Sydney, Australia, where he pursued his Ph.D. Degree. His current research interests include RF propagation, MIMO Space-Time channel measurements, characterization and channel modelling, smart antennas, MIMO systems and array signal processing.
Ananda S. Mohan is currently a member of the Faculty of Engineering, University of Technology, Sydney (UTS), Australia where he leads research on antennas, microwaves, wave propagation, and wireless technology. He received a Ph.D. degree in electrical communication engineering from the Indian Institute of Technology, Kharagpur, India and was a Scientist and Senior Scientist at the Research and Training Unit for Navigational Electronics, Hyderabad, India. At UTS, he directed the Sydney microwave design resource centre and was the associate program leader of the co-operative research centre for satellite systems. He currently directs the microwave and wireless technology research laboratory and a core member of the university research centre on health technologies. His current teaching and research interests include wireless mobile communications, microwaves and antennas, smart antennas and applications of microwave and wireless technology in medicine and has obtained many competitive research grants in these areas. Dr. Mohan was a co-recipient of the Priestly memorial award from the Institute of Radio and Electronic Engineers (IREE), Australia. He was a member of the organizing and technical Program Committees of the IEEE Globecom'98, APMC 2000, and International Symposium on Wireless Systems and Networks, 2003 and IASTED International Conference on Antennas, Radar, and Wave Propagation, for 2004 and 2005. 相似文献
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Wireless communication systems employing multiple antennas at both the transmitter and receiver have been shown to offer significant gains over single-antenna systems. Recent studies on the capacity of multiple-input-multiple-output (MIMO) channels have focused on the effect of spatial correlation. The joint effect of spatial and temporal correlation has not been well studied. In this paper, a geometric MIMO channel model is presented, which considers motion of the receiver and nonisotropic scattering at both ends of the radio link. A joint space-time cross-correlation function is derived from this model and variates with this joint correlation are generated by using the vector autoregressive stochastic model. The outage capacity of this channel is considered where the effects of antenna spacing, antenna array angle, degree of nonisotropic scattering, and receiver motion are investigated. When n transmit and n receive antennas are employed, it is shown that the outage capacity still increases linearly with respect to n, despite the presence of spatial and temporal correlation. Furthermore, analytical expressions are derived for the ergodic capacity of a MIMO channel for the cases of spatial correlation at one end and at both ends of the radio link. The latter case does not lend itself to numerical evaluation, but the former case is shown to be accurate by comparison with simulation results. The proposed analysis is very general, as it is based on the transmit and receive antenna correlations matrices. 相似文献
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Cetiner B.A. Jafarkhani H. Jiang-Yuan Qian Hui Jae Yoo Grau A. De Flaviis F. 《Communications Magazine, IEEE》2004,42(12):62-70
Multi-input multi-output systems with associated technologies such as smart antennas and adaptive coding and modulation techniques enhance channel capacity, diversity, and robustness of wireless communications as has been proven by many recent research results both in theory and experiments. This article focuses on the antenna aspect of MIMO systems. In particular, we emphasize the important role of the reconfigurable antenna and its links with space-time coding techniques that can be employed for further exploitation of the theoretical performance of MIMO wireless systems. The advantages of the reconfigurable antenna compared to the traditional smart antenna are discussed. Establishment of reconfigurable antennas requires novel radio frequency microelectromechanical systems technology, which has recently been developed in the authors' group. We briefly introduce this technology with emphasis on its distinct advantages over existing silicon-based MEMS technologies for reconfigurable antennas. A reconfigurable antenna design that can change its operating frequency and radiation/polarization characteristics is described. Finally, we present the experimental and theoretical results from impedance and radiation performance characterization for different antenna configurations. 相似文献