一种空间相关的Nakagami-m衰落下MIMO-OFDM系统误码率计算方法

为了获得Nakagami相关衰落下各参数对MIMO系统误码率的影响,首先给出了一种新的MI-MO-OFDM系统模型.接着对空间相关的基于STBC编码的MIMO-OFDM系统在Nakagami-m平坦衰落下的信道误码率进行了研究,给出了一种误码率的表达式,分析了空间相关性和分布参数对系统的误码率的影响.最后给出空间相关条件下的STBC的误码率性能仿真,以验证理论分析的有效性.结果表明,在Rayleigh和Rice分布都不足以描述信道特性的情况下,采用Nakagami分布比较吻合实际测量的数据,信道衰落基于Nakagami-m分布的STBC编码能很好的满足MIMO-OFDM系统的差错性能要求.     

基于MapViewer的LBS系统应用研究和实现

该文介绍了MapViewer的基本构成和技术特点,研究和分析了以MapViewer与Oracle空间数据库相结合开发基于位置的服务系统的总体体系结构和实现原理,构建并实现了一种的基于Mapviewer平台的基于位置服务的应用,即在地图上的范围查询服务.最后总结了基于位置服务的技术具有广阔的应用前景和巨大的商业发展潜力.     

Multiuser beamforming based on max SINR for downlink spatial multiplexing MIMO

In this article, a method based on max signal interference noise ratio (SINR) criterion is proposed, to mitigate the interuser interference for downlink multiuser spatial multiplexing multi-input multi-output (MIMO) systems.Unlike the zero forcing (ZF) scheme in which the SNR is decreased when the interference is eliminated completely, max SINR method makes a compromise between noise and interuser interference.When the number of substreams is larger than the difference between the number of base station antennas and the sum of interference mobile station antennas, the ZF is infeasible.An existing coordinated TX-RX block diagonalization (COOR BD) method uses preprocessing at the receiver to cancel the interuser interference.However, it cannot obtain more receive diversity gain because of the preprocessing.Analysis and simulation show that the max SINR scheme has better performance than the ZF method.Moreover, when the ZF is infeasible, the max SINR scheme can obtain more receive diversity gain than COOR BD in the two-user case.     

WIMAX系统中的多天线技术及应用

WiMAX（全球互通微波接入）技术近年来发展迅速,逐渐成为宽带无线接入技术的热点之一。WiMAX系统能够实现高于2bps/Hz的频带利用率。为了增加覆盖范围和系统的可靠性,IEEE802.16标准支持Alamouti方案的空时码（STC）、自适应天线（AAS）和多输入多输出（MIMO）技术在内的多天线技术。多天线技术的应用能显著地提高系统容量和频谱利用率,从而大大增强WiMAX技术的竞争力。     

Spatial dynamics and genetics of infectious diseases on heterogeneous landscapes.

Explicit spatial analysis of infectious disease processes recognizes that host-pathogen interactions occur in specific locations at specific times and that often the nature, direction, intensity and outcome of these interactions depend upon the particular location and identity of both host and pathogen. Spatial context and geographical landscape contribute to the probability of initial disease establishment, direction and velocity of disease spread, the genetic organization of resistance and susceptibility, and the design of appropriate control and management strategies. In this paper, we review the manner in which the physical organization of the landscape has been shown to influence the population dynamics and spatial genetic structure of host-pathogen interactions, and how we might incorporate landscape architecture into spatially explicit population models of the infectious disease process to increase our ability to predict patterns of disease occurrence and optimally design vaccination and control policies.     

Research on Evaluation of Degree of Complexity of Mining Fault Network Based on GIS

A large number of spatial and attribute data are involved in coal resource evaluation. Database is a relatively advanced data management technology, but its Major defects are the poor graphic and spatial data functions, from which it is difficult to realize scientific management of evaluation data with spatial characteristics and evaluation result maps. On account of these deficiencies, the evaluation of degree of complexity of mining fault network, based on GIS, is proposed, which integrates management of spatial and attribute data. Fractal is an index which can reflect the comprehensive information of faults＇ number, density, size, composition and dynamics mechanism. Fractal dimension is used as the quantitative evaluation index. Evaluation software has been developed based on a component GIS-MapX, with which the degree of complexity of fault network is evaluated quantitatively using the quantitative index of fractal dimensions in Liuqiao No.2 coal mine as an example. Results show that it is effective in acquiring model parameters and enhancing the definition of data and evaluation results with the application of GIS technology. The fault network is a system with fractal structure and its complexity can be described reasonably and accurately by fractal dimension, which provides an effective method for coal resource evaluation.     

基于微焦斑源X射线传播的相衬成像模拟

从标量衍射及部分相干光衍射理论出发,结合硬X射线特点,建立基于微焦斑X射线源的衍射成像模型.该模型将Fresnel积分运算转换到空间频域,利用快速傅里叶变换计算衍射光场.根据部分相干光理论分析,有限大小光源的物体衍射光场为光源光强分布与点源所形成的物体衍射光场的卷积,将卷积运算转换到空间频域并利用快速傅里叶变换算法提高运算速度.模拟衍射结果表明,物体到X射线源的距离、X射线光子能量以及X射线源焦斑尺寸均影响自由空间传播相衬成像系统的图像衬度.研究结果有助于X射线相衬成像系统的设计和性能优化.     

角色群体协作中的层次感知模型研究

群体感知是群体协作有效进行的前提条件.在分析当前群体感知模型及群体协作模型研究现状的基础上,以角色为协作基础,根据任务相关度、协作者间组织结构的紧密程度来进行分层感知,提出了一种支持层次角色群体感知的模型(role based hierarchical awareness model,简称RHAM).RHAM 首先构建了一个群体协作环境(group cooperation environment,简称GCE),然后在GCE 的基础上扩展定义群体协作感知内容、感知层次及感知相关特性.最后对该模型的应用进行了     

基于集合论的煤矿床空间数据模型研究

为了有效地表达现实世界特别是煤矿床的三维空间实体，在分析了复杂煤层三维数据的基础上，基于集合论的数学思想，提出了一种新的抽象的煤矿床空间数据模型．该模型把三维空间数据分解为三维点、线、简单面、面、体等5种空间数据模型，通过模型的相关性进行适当的集合运算，从而得出空间真三维煤矿床实体．并以断层为实例，给出了相应模型表示及其相应的集合运算，即集合间并、交、差等相关操作，从而生成三维煤矿床断层．结果表明：这种模型可以较为有效地表达煤矿床三维空间实体，为进一步研究奠定了基础．     

基于四叉树的海量空间数据模型研究

地理信息系统的发展与应用，导致空间数据不断增长。数据量大、信息量多，内容丰富是空间数据的特点。针对全球海量空间数据的特点，提出了一种基于四叉树的空间数据模型，合理地对空间数据存储空间进行分配，很好地解决了海量空间数据的高效存取问题。