A new spatial path persistency model for TOA-based indoor geolocation

Analysis of the persistency and birth/death of multipath components of the channel impulse response is essential for performance evaluation of indoor geolocation algorithms using indirect paths for ranging. The use of indirect paths via multipath diversity is particularly important for situations where the direct path gets blocked. In this letter, we propose a statistical model for the spatial behavior of the persistency of multipath components as a mobile moves inside a building. Based on empirical data from a measurement calibrated ray tracing algorithm we show that the persistency in a typical building is modeled by log-logistic distribution rather than commonly assumed exponential distribution and path birth can be modeled as a Poisson distribution.     

Empirical pathloss model for indoor geolocation using UWB measurements

A novel empirical approach is presented for modelling the path loss behaviour of the direct path (DP) between the transmitter and receiver, which is important for time-of-arrival-based indoor geolocation coverage characterisation. Using ultra wideband (UWB) measurements in four sites and three ranging scenarios, pathloss models at 500 MHz and 3 GHz system bandwidths are provided, centred on 4.5 GHz for DP and total signal power. In addition, ranging coverage analysis is provided using the DP models     

A substrate-dependent CAD model for ceramic multilayer capacitors

In this paper, a substrate-dependent lumped-element model for ceramic multilayer capacitors is presented. The height and dielectric constant of a substrate have a significant impact on the frequency response of a chip capacitor, and these effects cannot be treated independently from the capacitor model. Rather, the equivalent-circuit parameters in the model must be made to vary in accordance with changes in the substrate. The model presented in this paper is suitable for microstrip-mounted components, and has been applied up to 10 GHz for values from 0.5 pF to 0.47 μF, and for FR-4 substrates ranging in height from 5 to 62 mil. The modeling and extraction procedure is demonstrated for 0805- and 1206-style capacitors     

A multilayer exponential model for spreading resistance calculations

A new multilayer approach to spreading-resistance correction-factor calculations is proposed, based on the approximation of the graded resistivity profile by a series of exponential functions. The existence of a recurrence formula for the integration factor in the correction factor integral makes the proposed model a practical alternative to Schumann and Gardner's staircase model. Although a factor of 3 slower in terms of computation time, the exponential model yields results much closer to the true profile than the staircase model, particularly in cases where the profile has very steep gradient but where the available measurement data points are sparse.     

Markov model for dynamic behavior of ranging errors in indoor geolocation systems

Recently, considerable attention has been devoted to modeling and analysis of the behavior of the ranging error in indoor environment. The ranging error modeling is essential in design of precise time of arrival (TOA) based indoor geolocation systems. In this paper we present a new framework for simulation of the dynamic spatial variations of ranging error observed by a mobile user based on an application of Markov model. The model relegates the behavior of ranging error into four main categories associated with four states of the Markov process. The parameters of the model are extracted from empirical data collected from a measurement calibrated ray tracing (RT) algorithm in a typical office environment. Results of simulated errors from Markov model and actual errors from empirical data show close agreement.     

高精度机载可见光图像定位方法

针对现有技术不能解决机载可见光图像快速自动定位的问题,提出了一种定位精度高、处理速度快、可扩展性好的机载可见光图像定位方法.该方法以传感器共线成像模型为中心,将实时图像和传感器成像参数送入共线模型进行正射校正,校正后的图像与相应的基准图像进行图像配准,使用配准同名点信息更新传感器成像参数,最后再次通过共线模型获取实时图地理坐标定位信息.这种通过图像配准再计算成像模型的间接定位方法,不仅减少了计算量,而且使自动配准算法稳定,较传统的直接定位方法或图像配准方法有突出的优势.此外,该方法具有严格的误差传递计算公式,能计算定位结果的误差.仿真实验表明即使在大倾斜角条件下,该方法也能获得优于100 m的定位精度.     

A MULTILAYER FEEDFORWARD NEURAL NETWORK MODEL FOR VISUAL MOTION PERCEPTION

The local visual motion detection mechanism used in the visual systems of primatescan only sense the motion component oriented perpendicularly to the contrast gradient of thebrightness pattern.But the visual system of higher animals can adaptively determine the actualdirection of motion through a learning process.In this paper a multilayered feedforward neuralnetwork model for perception of visual motion is presented.This model employs W.Reichardt'selementary motion detectors array and T.Kohonen's self-organizing feature map.We explored theself-organizing principles for perception of visual motion.The computer simulations show thatthis neural network is able to recognize the true direction of motion through an unsupervisedlearning process.In addition,the neurons with the same or similar motion direction selectivitytend to appear in“functional columns”which seem to be qualitatively similar to the corticalmotion columns observed by electrophysiological and cytohistochemical studies in certain higherareas such as MT.It proves that motion-detection by spatio-temporal coherences,mapping,co-operation,competition,and Hebb rule may be the basic principles for the self-organization ofvisual motion perception networks.     

A process simulation model for multilayer structures involving polycrystalline silicon

The increasing complexity of VLSI fabrication often requires the use of multilayer structures above the silicon substrate. Electrical and metallurgical properties of multilayer structures have an important effect on circuit performance and reliability. Although process simulation models are available and widely used for computer-aided process design, none of the existing process simulation programs have the capability for modeling multilayer structures. A new model with such capability has been developed and this paper presents the physics as well as the results of simulation supported by experimental data. The model can simulate many desirable properties of multilayer structures involving polycrystalline silicon, such as grain growth, resistivity and oxidation rate of the polysilicon layer, the impurity redistribution across multilayers after high-temperature thermal processing, impurity segregation both at grain boundaries and at interfaces, and the interdependent phenomena of dopant-dependent oxidation/diffusion.     

A novel user satisfaction prediction model for future network provisioning

The notion of user perception has grown in terms of its importance and complexity. This paper presents results of an experimental study focused on predictive modeling of the relations between the user perception, user satisfaction and objective technical parameters in data communication services. A new model for prediction of user satisfaction was devised using probability theory based on Markov chain. Two experiments were completed for web browsing scenarios. The results of the first experiment have confirmed that previous user experience has significant effect on the user perception of quality and should represent a vital element of future predictive user models. The result of the second experiment is a user satisfaction prediction model, which presents a novel insight and deeper understanding of user perception of quality. This model can significantly improve level of user satisfaction with services in telecommunications systems if implemented within advanced system design, optimization and quality assurance procedures.     

A multipath-driven approach to HF geolocation

A method is proposed for HF emitter geolocation and mode group-range estimation when the signal of interest is received via skywave propagation by a uniform linear array (ULA) of antennas at a single site. Ionospheric multipath and the geometrical relationships that constrain such propagation are exploited to derive a new class of estimator for a problem that inherently produces an ambiguous solution when the modes are considered individually. The introduced multipath-driven approach resolves the coning ambiguity and opens up the possibility to perform meaningful HF single site location (SSL) with a ULA. The method is also applicable to reduce estimation errors in traditional HF-SSL systems based on two-dimensional apertures. Field-data gathered in a controlled experiment with known truth is used to validate the method.     

A model of the interdiffused multilayer process

The interdiffused multilayer process (IMP) is a novel approach to growing Hg_1−xCd_xTe. In this process, alternating thin films of HgTe and CdTe are grown and allowed to interdiffuse resulting in a bulk material of constant composition. A model of the IMP must include the effects of both the deposition of new material and the interdiffusion of the material. It must also be able handle the flush phases of the IMP where the growth rate decays to zero. Existing approaches to modeling epitaxial growth of Hg_1−xCd_xTe treat growth and interdiffusion as separate, sequential steps resulting in numerical stability problems, pseudodiffusion effects, or flush phase modeling problems. The model presented here, however, is based on an incremental balance where growth and diffusion occur simultaneously, resulting in a model exhibiting none of the difficulties mentioned above. The IMP growth model is integrated with a model for calculating reflectance from a laser directed at near normal incidence angle. The predicted reflectance is compared to experimental measurements and showed a good preliminary fit when the model employed default parameters. The agreement is greatly improved after parameter fitting.     

A multiservice user descriptive traffic source model

The asynchronous transfer mode (ATM)-based broadband integrated services digital network (B-ISDN) dominates the research interest in telecommunications. Traffic and network modeling are the techniques used for performance evaluation and assessment of B-ISDN design alternatives and planning. The specific nature of the ATM technique requires new approaches for traffic modeling. Selecting appropriate traffic source models is an important issue, since it is closely related to the successful design and efficient performance of the networks to be built in the future. The source (multilevel, multiservice structured Markovian) model presented provides a simple way for characterizing the behavior of a telecommunication user recognizing the multilevel discipline of a telecommunication session. The traffic model is general enough to fit a variety of different services by appropriately varying the values of the parameters defining it, but also it is simple enough because it is described by a small number of parameters and the defining parameters make a good intuitive sense by being closely related to actual physical quantities     

A derived physically expressive circuit model for multilayer RF embedded passives

In this paper, a derived physically expressive circuit model is presented for automatically deriving an equivalent-circuit model of a multilayered embedded RF passive. The scheme is based on the partial-element equivalent-circuit (PEEC) model and a simple circuit transformation. By defining an appropriate cutoff criterion that is related to the highest frequency of interest, most of the internal nodes in the coupling circuit generated by the PEEC model can be approximately absorbed by the remaining frequency-independent LC elements progressively. The model is very simple to implement and has apparent physical meaning. Mathematically, this model progressively recombines the least significant system pole with other less significant poles. The resultant physically expressive circuit model will be very useful in designing multilayer embedded RF circuits. Four examples are given for demonstrating the validity and effectiveness of the scheme.     

A combined self-organizing feature map and multilayer perceptronfor isolated word recognition

A neural network system which combines a self-organizing feature map and multilayer perception for the problem of isolated word speech recognition is presented. A new method combining self-organization learning and K-means clustering is used for the training of the feature map, and an efficient adaptive nearby-search coding method based on the `locality' of the self-organization is designed. The coding method is shown to save about 50% computation without degradation in recognition rate compared to full-search coding. Various experiments for different choices of parameters in the system were conducted on the TI 20 word database with best recognition rates as high as 99.5% for both speaker-dependent and multispeaker-dependent tests     

Object recognition using multilayer Hopfield neural network

An object recognition approach based on concurrent coarse-and-fine matching using a multilayer Hopfield neural network is presented. The proposed network consists of several cascaded single-layer Hopfield networks, each encoding object features at a distinct resolution, with bidirectional interconnections linking adjacent layers. The interconnection weights between nodes associating adjacent layers are structured to favor node pairs for which model translation and rotation, when viewed at the two corresponding resolutions, are consistent. This interlayer feedback feature of the algorithm reinforces the usual intralayer matching process in the conventional single-layer Hopfield network in order to compute the most consistent model-object match across several resolution levels. The performance of the algorithm is demonstrated for test images containing single objects, and multiple occluded objects. These results are compared with recognition results obtained using a single-layer Hopfield network.     

Radar backscattering model for multilayer mixed-species forests

A multilayer canopy scattering model is developed for mixed-species forests. The multilayer model provides a significantly enhanced representation of actual complex forest structures compared to the conventional canopy-trunk layer models. Multilayer Michigan Microwave Canopy Scattering model (Multi-MIMICS) allows overlapping layer configuration and a tapered trunk model applicable to forests of mixed species and/or mixed growth stages. The model is the first-order solution to a set of radiative transfer equations and includes layer interactions between overlapping layers. It simulates SAR backscattering coefficients based on input dimensional, geometrical, and dielectric variables of forest canopies. The Multi-MIMICS is an efficient realization of actual forest structures and can be shaped for specific interest of forest parameters. We present the model's application and validation in the paper. The model is parameterized using data collected from a 220,000-ha area of forests in central Queensland, Australia. Fifteen 50/spl times/50 m test sites representing the general forest diversity and growth stages are chosen as ground truth. Polarimetric backscattering airborne SAR (AIRSAR) data of the same area are acquired to validate the model simulations. The model predicts SAR backscattering coefficients of the test areas. Simulation results show a good agreement with AIRSAR data at most frequencies and polarizations. The simulated backscattering coefficient from the multilayer model and the standard MIMICS are also compared and significant improvements are observed.     

基于国家电波观测站网信号的短波机动用户位置认知方法

短波通信中频率选择是提高通信质量的必要手段,但短波机动用户却难以获取选频链路计算需要的位置信息. 文中设计了一种随时可利用多站信号进行机动终端位置认知的方法. 逆向应用时差定位原理,通过机动终端接收到的三个站点信号的两两信号时延差与虚路径差成正比,形成两条双曲线,交点就是机动用户的位置. 算法的关键是利用国家电波观测站网常态化发射的探测信号,同时设计了基于网格化预测时差与实测时差之间误差的位置概率函数,将定位问题转化为概率选择问题. 仿真分析和实测数据都验证了算法的可行性. 最后讨论了几种算法的改进策略,有望尽快实现工程应用.     

Exact closed-form geolocation for SAR interferometry

Exact closed-form algorithms for InSAR-derived digital elevation model (DEM) geolocation are described. They are based on the knowledge of orbit parameters and time/Doppler frequency coordinates of each SAR image, as well as of their interferometric phase. The proposed scheme gives a simple framework for deriving the geolocation accuracy     

A CASCADED MODEL OF NEURAL NETWORK FOR PATTERN RECOGNITION

A cascaded model of neural network and its learning algorithm suitable for opticalimplementation are proposed.Computer simulations have shown that this model may successfullybe applied to an error-tolerance pattern recognitions of multiple 3-D targets with arbitrary spatialorientations.     

一种基于信任度的朋友推荐模型

针对如何对交友网站中的用户进行朋友推荐的问题,提出一种依据信任度进行朋友推荐的模型。通过用户之间的信任关系,建立信任模型,计算出该用户和其信任距离在3个跳转之内的所有其他用户的信任度。在计算用户之间的间接信任度时引入了衰减因子,改进了常见的间接信任度算法,从而达到依据信任度的高低依次对用户进行朋友推荐的目的。通过应用该模型对一个实例模型关系进行分析的结果表明,该朋友推荐模型能够有效地对用户进行朋友推荐,体现了用户对于有直接指向关系用户的信赖程度。