914 MHz path loss prediction models for indoor wirelesscommunications in multifloored buildings

Qualitative models are presented that predict the effects of walls, office partitions, floors, and building layout on the path loss at 914 MHz. The site-specific models have been developed based on the number of floors, partitions, and concrete walls between the transmitter and receiver, and provide simple prediction rules which relate signal strength to the log of distance. The standard deviation between measured and predicted path loss is 5.8 dB for the entire data set, and can be as small as 4 dB for specific areas within a building. Average floor attenuation factors, which describe the additional path loss (in decibels) caused by floors between transmitter and receiver, are found for as many as four floors in a typical office building. Path loss contour plots for measured data are presented. In addition, contour plots for the path loss prediction error indicate that the prediction models presented are accurate to within 6 dB for a majority of locations in a building     

A microcellular communications propagation model based on theuniform theory of diffraction and multiple image theory

Presents a comprehensive uniform theory of diffraction (UTD) propagation model for a city street grid, using the multiple image concept and the generalized Fermat's principle to describe the multiple reflections and diffractions. The model is a quasi 3D one in the sense that the building walls are assumed to be much higher than the transmitter height so that the diffractions from the rooftops can be neglected. The model includes all possible specular wall and ground reflections and corner diffractions in the main street, side streets, and parallel streets of a microcell. This enables the signal propagation through all the possible paths to be tracked to the receiver at various line-of-sight (LOS) or out-of-sight (OOS) positions. Previous papers on such propagation models have included only a limited number of specular reflections and diffractions or they are restricted to a rectilinear grid where all the building walls on each side of the street are coplanar. Our model includes contributions to the received signal from all possible propagation paths, including ground and wall reflections from diffracted and specularly reflected signals both in the LOS and OOS regions. Within the scope of the UTD model, the accuracy of our model is limited mainly by the assumptions of characterizing the building walls as “smoothed-out” flat surfaces with average relative permittivity ϵ_r and conductivity σ. Our theoretical results of the signal path loss along the streets are compared with measurements which have been reported for city streets in Tokyo and New York City     

Effective models in evaluating radio coverage on single floors ofmultifloor buildings

An effective site-specific hybrid model is developed to predict the path loss and the effective radio coverage on single floors. The hybrid model, combined with a two-dimensional (2-D) model and an easy-to-use direct-transmitted ray (DTR) model, is incorporated with the building blueprint in usage. Both effects of the interior walls and the metallic objects such as whiteboards, bookcases, and standing air conditioners on radio propagation are considered. It is found that inclusion of metallic objects will enhance the performance of the model     

A building-transmission model for improved propagation prediction in urban microcells

This paper presents a model for the propagation of radiowaves through buildings. The model can be used as a seamless extension to ray-based propagation prediction models that only consider external reflection and diffraction, as do most current models. This involves the use of so-called transmitted rays, which are traced through building walls. Outdoor-to-indoor propagation (building penetration) is automatically taken into account as a "by-product". The transmission model requires no information about each building's interior other than a specific attenuation factor that describes the global behavior of the field inside the building. This coefficient can be determined for individual buildings by measuring the excess loss associated with the propagation path through the building. It is shown, however, that no large errors are to be expected if all buildings are characterized by the average of the empirical values obtained in this study, at 1.9 GHz. Path loss predictions generated with the aid of the new model are shown and compared with measured data to illustrate the considerable improvement in accuracy that can be achieved in realistic urban microcell scenarios by taking into account building penetration and transmission.     

Wideband radio propagation modeling for indoor geolocationapplications

A framework for statistical modeling of the wideband characteristics of the frequency-selective fading multipath indoor radio channel for geolocation applications is presented. Multipath characteristics of the channel are divided into three classes according to availability and the strength of the direct line of sight (DLOS) path with respect to the other paths. Statistics of the error in estimating the time of arrival of the DLOS path in a building is related to the receiver's sensitivity and dynamic range. The effects of external walls on estimating the location of the DLOS path are analyzed     

Slant path rain attenuation and path diversity statistics obtained through radar modeling of rain structure

Single and joint terminal slant path attenuation statistics at frequencies of 28.56 and 19.04 GHz have been derived employing a radar data base obtained over a three-year period at Wallops Island, VA. Statistics were independently obtained for path elevation angles of20deg,45deg, and90degfor purposes of examining how elevation angles influences both single terminal and joint probability distributions. Both diversity gains and autocorrelation function dependence on site spacing and elevation angles were determined employing the radar modeling results. Comparisons with other investigators are presented. An independent path elevation angle prediction technique was developed and demonstrated to fit well with the radar derived single and joint terminal radar derived cumulative fade distributions at various elevation angles.     

Refocusing Through Building Walls Using Synthetic Aperture Radar

Through-wall imaging/sensing using a synthetic aperture array technique is studied by employing ultrawideband antennas and for wide incidence angles. The propagation through building walls, such as brick and poured concrete in response to point sources near the walls, is simulated by using high-frequency methods. Reciprocity is used to find the responses of point targets behind walls, which are then used to simulate the synthetic aperture radar (SAR) imaging through the walls. The effect of building walls on the target-image distortions is investigated by simulations and measurements. It is shown that by using the idea of match filtering, the effect of the wall can be compensated for, and the point target response can be reconstructed, provided that the wall parameters are known. An optimization method based on minimization of squared error in the SAR image domain within an area confined within the expected point-spread function is used to estimate the wall parameters and sharpen the image simultaneously. A controlled experiment within the laboratory environment is performed to verify the methods presented. It is shown that for an ultrawideband system operating over a frequency band of 1-3 GHz, highly distorted images of two point targets in close proximity of each other behind a wall can be resolved after refocusing. A dual-frequency synthetic method is also presented that can improve the cross-range resolution of the refocused image.     

Tropospheric microwave propagation--An X band diagnostic system

A microwave system for direct measurement of angles of arrival and multipath delay times is described. Based on the utilization of interferometer and very wide frequency sweeping (1- GHz range) techniques, high accuracy measurements on these parameters are possible. Some experimental results are presented which suggest that movements in the angle of arrival of a single ray path (as opposed to multipath) may be responsible for much of the fading experienced on light-of-sight microwave links in southwestern Ontario.     

A model to describe the distribution of transmission path elevationangles to the Iridium and Globalstar satellite systems

The quality of a satellite-based personal communications system (S-PCS) transmission path is heavily influenced by its elevation angle. The distribution of path elevation angles varies with a user's latitude but can be characterized by a single distribution with changing parameters. Through simulation, model fitting and regression analysis, a set of equations is presented which allows the distribution of elevation angles to both Globalstar and Iridium systems to be determined for any point on the Earth between ±60° latitude     

Clustering and learning Gaussian distribution for continuous optimization

Since the Estimation of Distribution Algorithm (EDA) was introduced, different approaches in continuous domains have been developed. Initially, the single Gaussian distribution was broadly used when building the probabilistic models, which would normally mislead the search when dealing with multimodal functions. Some researchers later constructed EDAs that take advantage of mixture probability distributions by using clustering techniques. But their algorithms all need prior knowledge before applying clustering, which is unreasonable in real life. In this paper, two new EDAs for continuous optimization are proposed, both of which incorporate clustering techniques into estimation process to break the single Gaussian distribution assumption. The new algorithms, Clustering and Estimation of Gaussian Network Algorithm based on BGe metric and Clustering and Estimation of Gaussian Distribution Algorithm, not only show great advantage in optimizing multimodal functions with a few local optima, but also overcome the restriction of demanding prior knowledge before clustering by using a very reliable clustering technique, Rival Penalized Competitive Learning. This is the first time that EDAs have the ability to detect the number of global optima automatically. A set of experiments have been implemented to evaluate the performance of new algorithms. Besides the improvement over some multimodal functions, according to the No Free Lunch theory, their weak side is also showed.     

Path Clustering for Test Pattern Reduction of Variation-Aware Adaptive Path Delay Testing

In this study, a novel path clustering technique for adaptive path delay testing, where the test paths are altered according to the extracted device parameters, is proposed. The proposed algorithm is based on the k-means++ algorithm. By considering the probability function of the die-to-die systematic process variation, the proposed algorithm clusters path sets to minimize the total number of test paths. A figure of merit for clustering, which represents the expected number of test paths, is also proposed for quantitatively evaluating path clustering under different conditions. The proposed clustering method is evaluated numerically by applying it to the OpenCores benchmark circuit. Using our clustering technique, the average number of test paths in the adaptive test is reduced to less than 92 % compared with those in the conventional test. In addition, adaptive testing using the proposed technique can reduce the test patterns by 94.26 % while retaining the test quality.     

Geometrical Spectrum Broadening in Ultrasonic Doppler Systems

The bandwidth of the output spectrum of blood flow meters may prove of value in estimating flow parameters such as the degree of turbulence. It is therefore important to determine the various factors which affect this bandwidth. It is shown that scatterers moving in the near field of the sound beam generated by a single transducer ultrasound Doppler system produce a spectrum whose breadth is primarily determined by the range of angles over which backscattered ultrasound is received by the transducer. An empirical method of calculating the bandwidth of the output spectrum is described, and the results are compared with direct Doppler measurements. Since the spectrum broadening depends on the angle between the target path and the ultrasound beam, it is suggested that the phenomenon may be usable to provide an independent measure of this angle.     

CATV return path characterization for reliable communications

The authors have examined the basic characteristics of hybrid-fiber coax (HFC) return systems to evaluate their ability to support bidirectional communications. The ability to support bidirectional communications on cable plants will allow deployment of two-way video applications as well as telecommunications services over the HFC plant. The results of the studies indicate that ingress in the cable return path is primarily due to broadcast signals which accumulate due to the noise-funneling effect of the cable return. Although this ingress can manifest itself in strong narrowband interferers which will prevent the use of large bandwidth channels, a reduction of node size to nodes on the order of 500 homes or lower will reduce the amount of interference. Filtering, in which a portion of the spectrum is blocked from the subscriber residence may also result in a significant reduction of ingress. Other phenomena on the return path can be dealt with by means of sound communication system design, including forward error correction to deal with impulse noise, and adaptive equalizers to deal with reflections in high data rate designs. TDMA, FDMA, and CDMA can all be utilized on the cable return path, but the capacities which result when less than perfectly synchronized CDMA is utilized are substantially lower than for TDMA and FDMA. A single carrier TDMA approach will be highly susceptible to narrowband interferers, and is unlikely to be successful. For these reasons a TDMA/FDMA or pure FDMA approach with narrow channels is likely to be the most robust multiple access technique for the cable return path     

X-ray microdiffraction investigation of crystallinity and strain relaxation in Ge thin lines selectively grown on Si(0 0 1) substrates

We used X-ray microdiffraction (XRMD) to investigate the crystallinity and strain relaxation of Ge thin lines with widths of 100, 200, 500 and 1000 nm selectively grown on Si(0 0 1) substrates using a patterned SiO₂ mask by chemical vapor deposition. The variations of the strain relaxation in the line and width directions were also investigated in Ge thin lines with a width of 100 nm. After growth, crystal domains with very small tilt angles were detected in Ge lines with all four line widths. The tilt angle range was larger in thinner Ge lines. After annealing at 700 °C, the formation of a single, large domain with a specific tilt angle was detected by XRMD for Ge thin lines with widths of 100 and 200 nm. These experimental results reflect the effects of SiO₂ side walls around the Ge thin lines on crystallinity and strain relaxation of Ge.     

The Impact of Reflections From Stratified Building Materials on the Wave Propagation in Future Indoor Terahertz Communication Systems

In order to derive reliable propagation models for future terahertz indoor pico-cellular communication systems, accurate reflectivity data of building materials is necessary. Here we present reflection terahertz time domain spectroscopy (THz-TDS) measurements and matching transfer matrix simulations of the frequency dependent reflection coefficient of multi layer building materials in the frequency range from 100 to 500 GHz for a set of angles, both in TE- and TM-polarization. Two prominent stratified structures, a double pane window and white paint on plaster are investigated as they usually account for large areas in indoor environments. Communication systems located above 100 GHz are expected to be strongly affected by the variations of the reflectivity over the frequency and incident angle of such stratified materials as they will rely both on line of sight (LOS) and non line of sight (NLOS) propagation. We discuss this impact on the power distribution in a sample scenario employing the ray-tracing method.     

基于相似性传播的天波雷达多路径量测聚类

电离层多层结构特性使得天波雷达(OTHR)与目标之间存在多条信号传播路径,进而可能对单目标产生多路径量测。该文考虑了天波雷达多路径量测聚类问题,其需要同时对多路径量测进行电离层传播路径辨识和聚类。由于天波雷达量测模型假设1个目标通过1种电离层传播路径至多产生1个量测,因此需要考虑多路径聚类约束。该文将相似性传播聚类扩展到多路径约束模型,并提出一种新的多路径相似性传播聚类算法。该算法通过构建多路径量测聚类的概率图模型,将聚类问题转化为概率图模型隐变量的推断问题,采用最大和置信传播算法近似求解聚类变量的最大后验概率。算法优点包括可以自动识别聚类团数目,单次消息传播的时间复杂度为量测个数和传播路径个数乘积的平方。仿真实验分析表明,所提算法较多路径多假设聚类算法具有更好的聚类性能。     

System Implications of 14/11 GHz Path Depolarization. Part II: Reducing the impairments

Dual-polarized co-channel operation via international communications satellites places stringent requirements on the amount of interference that can be allowed from all sources. System design must allow for the depolarization caused by rain and ice crystals, the principal source of additional interference. In the 14/11 and 14/12 GHz bands, some paths are depolarization limited, particularly at lower path elevation angles, or become so with up-link power control. Others are attenuation limited. Therefore, a means must be found to reduce the level of path depolarization to meet the requirements for path availability. In Part I or this paper, reference joint statistics of cross-polarization discrimination/attenuation statistics were derived for a number of paths and climates to establish the additional fade and cross-polarization discrimination margins required. This second paper addresses methods for reducing the system effects of path depolarization. Appropriate orientation of the polarization vectors at the spacecraft is shown to be an attractive alternative for spot-beam applications. For all other situations, it is concluded that single-parameter, phase-only compensation at the earth terminal will meet all practical system requirements.     

Image Segmentation by Hierarchical Spatial and Color Spaces Clustering

1IntroductionI mage segmentation, as a basic building block formany high-level i mage analysis problems ,such as objectrecognition[1], i mage retrieval[2], etc , has attractedmany research attentions over years .I mage segmenta-tionis to decompose the i mage into homogenous regionswiththe ai mof extractingthe major color andregionin-formationfromthe original i mage . The result of i magesegmentationis a set of non-overlapping regions whereeach regionis characterized by a chosen color and a con…     

基于无人机热成像的建筑饰面层脱粘缺陷识别

建筑外墙饰面层脱粘剥落广泛存在,对居民生命财产安全带来巨大威胁.本文以旋翼无人飞机为工作平台,搭载红外热成像相机对建筑外墙饰面层脱粘缺陷进行成像检测,获得脱粘缺陷热成像温度场分布规律;通过饰面层脱粘缺陷温度场、形状特征分析,提出基于热源聚类的脱粘缺陷红外图像分割方法,构建饰面层脱粘缺陷形状特征向量集,建立基于支持向量机...