The RCT approach for cell coverage prediction (II): Experiment and early results

We study on the implementation flow of the radio computerized tomography (RCT) prediction method. A case in real cellular mobile radio (CMR) system together with the prediction results are also presented. As shown by the results, the RCT prediction method is marked for its convenience and rapidity, as well as its relative high precision even when the prediction procedure is highly simplified. Since it is developed according to the characteristics of wireless communication environments of our country and has concurrently merits from both statistical and deterministic prediction models, the RCT prediction method is in good agreement with engineering practices in cellular mobile communication in cities at home. Optimized by combining with other techniques, further improvement could be achieved in the stability and precision of the RCT prediction method which now serves as the core part of a software tool for commercial use in CMR system analysis and optimization. Biography: Yu Sheng-bing (1974-), male, Ph. D candidate, research interest: theory analysis and application development of radio propagation in wireless communication systems.     

A Time‐Simultaneous Prediction Box for a Multivariate Time Series

A sample‐based method in Kolsrud (Journal of Forecasting 2007; 26 (3): 171–188) for the construction of a time‐simultaneous prediction band for a univariate time series is extended to produce a variable‐ and time‐simultaneous prediction box for a multivariate time series. A measure of distance based on the L_∞ ‐norm is applied to a learning sample of multivariate time trajectories, which can be mean‐ and/or variance‐nonstationary. Based on the ranking of distances to the centre of the sample, a subsample of the most central multivariate trajectories is selected. A prediction box is constructed by circumscribing the subsample with a hyperrectangle. The fraction of central trajectories selected into the subsample can be calibrated by bootstrap such that the expected coverage of the box equals a prescribed nominal level. The method is related to the concept of data depth, and thence modified to increase coverage. Applications to simulated and empirical data illustrate the method, which is also compared to several other methods in the literature adapted to the multivariate setting. Copyright © 2015 John Wiley & Sons, Ltd.     

基于DEM的民航地空VHF通信有效覆盖仿真研究

针对起伏地形环境下求解民航地空甚高频(very high frequency, VHF)通信有效覆盖范围冗余较大、精度较低的问题,采用改进的最大斜率法进行了仿真研究。首先,考虑遮蔽角计算存在计算冗余,提出"高程清洗"方法,降低计算量。其次,考虑求解最大斜率遮蔽角存在误差,采用改进的反距离加权插值法对原始数字高程模型数据进行插值提升分辨率,提高了切点逼近点位置精度。然后,为确定遮蔽区域具体点位,提出"切点截止法"进行求解。最后,为得到准确覆盖率,采用"网格法"分析计算。实验表明,改进的最大斜率法可有效减少计算冗余,提高信号覆盖求解精度,覆盖率相对改进前分别降低9.58%、4.10%和1.26‰。改进的VHF有效覆盖范围仿真程序可为VHF地面通信站选址、飞机航线规划提供支撑。     

Application of ERS-1 scatterometer data to studying land surfaces ──Distributive characteristic of backscattering coefficient over China land surfaces

ERS 1 WSC data were obtained by international cooperation. The distributive characteristics of radar backscattering coefficient image of China land surface are analyzed and the research results are presented. The capability of ERS 1 WSC data for monitoring land surfaces is investigated. The results show that the radar backscattering coefficient images can reveal the natural landform features of China land. Using the WSC data can discriminate six types of major land coverage, including evergreen vegetation and snow covered region, vegetation and crops, mountains, grassland, desert and grassland, desert. On the whole, the radar backscattering coefficient image of China land is the synthesis of the vegetation map and terrain map. Statistical study of the typical terrain shows that the radar backscatter coefficients of China land range from -29 dB to -5 dB. The lowest value corresponds to the deserts of Badain Jaran, Takla Makan, and Tengger. The highest value corresponds to snow covered regions of Himalaya Mountains and Tianshan Mountains.     

天山山地森林调节河川径流作用的探讨

运用天山北坡山地３１条河流的水、气象以及森林资源资料，分析森林调节河川年径流量作用，结果表明：森林与蒸发因素具有减少河川年径流量的效应，且森林调节河川径流量的作用远大于蒸发因素影响。在森林因素中，森林面积增加对河川年径流量的影响程度大于的作用远大于蒸发因素影响。在森林因素中，森林面积增加对河川年径流量的影响程度大于单位集水区面积森林蓄积量增加的作用，在天山北坡山地自然地理环境条件下，林率每增加１     

一种新的传感器监测网络密度控制算法

密度控制是传感器监测网络研究的核心内容之一.本文在Tian Di.的基于倡导区覆盖模型的密度控制算法SSC的基础上,提出了一种新的密度控制算法ESSC.该算法着重考虑了SSC算法的不足,修改了倡导区覆盖模型.理论分析和仿真结果表明,ESSC算法比SSC算法减少了约15%~25%的活动节点,同时又保证了一定的网络监测性能.     

基于改进灰狼优化算法的WSN覆盖优化

针对无线传感器网络（WSN）节点在随机部署时,存在分布不均匀的情况,从而导致覆盖率较低的问题,提出了一种改进的灰狼优化（GWO）算法.首先利用Tent混沌映射初始化种群,增加种群的多样性;其次利用改进的非线性收敛因子,平衡算法的全局搜索能力与局部搜索精度;最后将差分进化（DE）算法的变异、交叉的理念融入GWO算法,避免算法陷入局部最优,并提高算法的收敛速度.基本测试函数仿真结果验证了改进算法的有效性,随后将其应用于WSN覆盖优化问题,可以使节点的分布更加均匀,显著提高覆盖率,进而改善网络性能.     

基于程序图的路径测试

本文给出了一种利用程序图进行软件测试的路径测试方法。     

媒体报道、承销商声誉与IPO首日换手率

本文以2009-2014年IPO(initial public offerings)公司上市前信息市场为研究对象,研究了公司上市前一年媒体报道与IPO首日换手率之间的相关关系.结果发现媒体关注度会显著正向影响IPO首日换手率,但该状况仅在承销商声誉较低时适用,当承销商声誉较高时这种相关关系会被高声誉的承销商所释放的强信号所减弱.进一步地,文章依照2012-2013年的IPO停牌期间将样本划分为政策变动前和政策变动后两个子样本,发现政策变动后媒体情绪对IPO首日换手率的影响变得不显著,可能的原因是由于政策变动后媒体的信息传播效应被政策波动所掩盖.文章以一个清晰的信息市场作为样本选择来源以排除其他信息主体的干扰,证实了媒体在信息市场中的信息中介角色,但该角色需要在一定条件下才会显著发挥作用.     

基于虚拟势场和学习自动机的有向传感网覆盖控制

针对目前有向传感网中覆盖增强和冗余节点体眠调度算法存在的问题,提出虚拟势场结合学习自动机的覆盖控制算法.引入基于质心距离和重复感知率的虚拟力改进模型,综合考虑虚拟向心力和切向力对感知角度调整的影响,建立微观虚拟力与转动角度的关系模型,并根据网络整体覆盖率增长率对节点调整幅度进行宏观控制,合理调整节点感知方向.在此基础上,根据节点重复感知率和能量因素建立学习自动机与环境信息的交互机制,学习最优的冗余节点休眠调度策略.仿真实验结果表明,该算法能够显著增强网络覆盖,并有效地控制网络覆盖冗余.