RF Localization for Wireless Video Capsule Endoscopy

RF localization science and technology started with the global positioning systems for outdoor areas, and it then transformed into wireless indoor geolocation. The next step in the evolution of this science is the transformation into RF localization inside the human body. The first major application for this technology is the localization of the wireless video capsule endoscope (VCE) that has been in the clinical arena for 12?years. While physicians can receive clear images of abnormalities in the gastrointestinal tract with VCE devices, they have little idea of their exact location inside the GI tract. To localize intestinal abnormalities, physicians routinely use radiological, endoscopic or surgical operations. If we could use the RF signal radiated from the capsule to also locate these devices, not only can physicians discover medical problems, but they can also learn where the problems are located. However, finding a realistic RF localization solution for the endoscopy capsule is a very challenging task, because the inside of the human body is a difficult environment for experimentation and visualization. In addition, we have no-idea how the capsule moves and rotates in its 3D journey in this non-homogeneous medium for radio propagation. In this paper, we describe how we can design a cyber physical system (CPS) for experimental testing and visualization of interior of the human body that can be used for solving the RF localization problem for the endoscopy capsule. We also address the scientific challenges that face and the appropriate technical approaches for solving this problem.     

Precision of RSS-Based Localization in the IoT

International Journal of Wireless Information Networks - Currently, the most popular indoor geolocation technique used in smart device is the RSS-based Wi-Fi localization. The general accuracy of...     

Performance Analysis of RSS-Based Localization in Wireless Sensor Networks

Wireless Personal Communications - In this paper, localization error of the received signal strength (RSS)-based method in mixed LOS/NLOS conditions is analysed. In contrast to the time of arrival,...     

Comparative Performance Evaluation of RF Localization for Wireless Capsule Endoscopy Applications

This paper presents an assessment of the accuracy of cooperative localization of a wireless capsule endoscope (WCE) using radio frequency (RF) signals with particular emphasis on localization inside the small intestine. We derive the Cramer–Rao lower bound (CRLB) for cooperative location estimators using the received signal strength (RSS) or the time of arrival (TOA) of the RF signal. Our derivations are based on a three-dimension human body model, an existing model for RSS propagation from implanted organs to the body surface and a new TOA ranging error model for the effects of non-homogeneity of the human body on TOA of the RF signals. Using models for RSS and TOA errors, we first calculate the 3D CRLB bounds for cooperative localization of the WCE in three major digestive organs in the path of GI tract: the stomach, the small intestine and the large intestine. Then we analyze the performance of localization techniques on a typical path inside the small intestine. Our analysis includes the effects of the number of external sensors, the external sensor array topology, number of WCEs used in cooperation and the random variations in the transmitted power from the capsule.     

Deployment of RSS-Based Indoor Positioning Systems

Location estimation based on Received Signal Strength (RSS) is the prevalent method in indoor positioning. For such positioning systems, a massive collection of training samples is needed for their calibration. The accuracy of these methods is directly related to the placement of the reference points and the radio map used to compute the device location. Traditionally, deploying the reference points and building the radio map require human intervention and are extremely time-consuming. In this paper we present an approach to reduce the manual calibration efforts needed to deploy an RSS-based localization system, both when using only one RF technology or when using a combination of RF technologies. It is an automatic approach both to build a radio map in a given workspace by means of a signal propagation model, and to assess the system calibration that best fits the required accuracy by using a multi-objective genetic algorithm.     

Accuracy of Dipole Localization with a Spherical Homogeneous Model

Dipole localization methods (DLM's) with a spherical, homogeneous, isotropic model were applied to the problem of locating and characterizing simulated dipole sources of the brainstem acoustic evoked response (BAER) in cats. Dipole source parameters considered were chosen to be consistent with measurements of gross potential within the brainstem during the BAER. The steepest ascent method was used to solve the least-squares minimization problem on a set of noiseperturbed surface voltages to obtain parameters of a single assumed dipole source. The magnitudes of errors in dipole postion and in dipole moment vectors were calculated for two surface voltage location sets, two assumed dipole source locations, and a range of surface signal-to-noise ratios. An approximate analytic approach to the simulation results attributed DLM errors to an apparent "noise dipole" calculated as the dipole term in the multipole expansion of the added surface noise. The standard deviation of the "noise dipole" magnitude was directly proportional to the standard deviation of surface noise voltage and inversely proportional to the root of the number of surface voltages. This analytic result was in general agreement with the mean of the dipole moment parameter errors in the simulation study. It was found that recalculation of the surface voltage set from the solution dipole of the simulation problem or from the "noise dipole" of the analytic treatment resulted in an improvement of signal-to-noise ratio at the surface.     

On Boosting the Accuracy of Non-RF to RF Correlation-Based Specification Test Compaction

Several existing methodologies have leveraged the correlation between the non-RF and the RF performances of a circuit in order to predict the latter from the former and, thus, reduce test cost. While this form of specification test compaction eliminates the need for expensive RF measurements, it also comes at the cost of reduced test accuracy, since the retained non-RF measurements and pertinent correlation models do not always suffice for adequately predicting the omitted RF measurements. To alleviate this problem, we explore several methodologies that estimate the confidence in the obtained test outcome. Subsequently, devices for which this confidence is insufficient are retested through the complete specification test suite. As we demonstrate on production test data from a zero-IF down-converter fabricated at IBM, the proposed methodologies overcome the inability of standard specification test compaction methods to reach industrially acceptable test quality levels, and enable efficient exploration of the tradeoff between test accuracy and test cost.     

用幅度矢量合成定位法改进HRTF的定位效果

为了改进虚拟3D立体声技术的定位准确性,依据头相关传递函数(HRTF)的原理,采用CIPIC实验室根据KEMAR假人头测得的HRTF数据,利用多媒体计算机合成了两通道虚拟3D立体声。通过对HRTF在声源前后定位的“混淆锥”问题的分析,提出了用幅度矢量合成定位(VBAP)方法改进定位效果。实验结果证明,使用VBAP改进后的HRTF能够显著提高声源前后定位的准确性,表明VBAP的声音加权能够对HRTF的混淆锥问题有较大改进。     

射频功率测量误差分析及其精度改善方法

通过对水负荷射频功率测量问题的深入研究，详细分析了阻抗失配损耗引起的测量误差的机理，得到了失配损耗与工程可操作的参数——驻波比间的关系式，由计算机仿真出了可用于工程实践的曲线，并提出了一种基于一次反射的提高功率测量精度的方法。为通用型磁控管测试设备提高测量精度提供了理论依据和工程应用的精度改善方法，具有效强的应用价值。     

基于DV-Hop算法的无线传感器网络定位精度优化

在无线传感器网络定位领域,DV-Hop算法因其实现简单得以广泛使用.针对DV-Hop算法定位误差较大的问题,提出一种基于DV-Hop多通信半径的加权定位算法.该算法利用多通信半径并通过引入修正因子细化和优化跳数,利用最小均方误差准则和加权方式修正平均跳距,并利用加权最小二乘法估算未知节点坐标.通过仿真得出所提算法在相同实验条件下的定位精度较DV-Hop算法提升约60.5％,相较于双通信半径优化算法和3-DV-Hop算法分别提升约36.4％和13.8％.     

多雷达定位的动态加权融合算法及其精度分析

为进一步提高多雷达系统的定位精度,分析了各雷达的测量精度随目标-雷达相对位置的实时变化情况。根据雷达的标称精度和雷达-目标的相对位置关系,推导了雷达测量精度的动态表达式,并对每个观测按精度进行最优加权,从而得到了最优权值计算公式。计算了固定权系数加权平均法和动态加权融合法所能达到的定位精度,分析了它们的定位精度几何稀释。蒙特卡罗仿真表明,与前者相比,后者的定位精度有很大提高。     

基于白光LED的室内高精度定位算法的实现

搭建了室内可见光定位系统,实验上探索了接收信号强度比定位算法的可行性.通过控制多个LED光源在不同时隙的亮暗,分别传输直流与正弦信号,使用照度计及光电探测器测试接收信号强度,对接收机位置进行了估计.其中使用直流信号时,在与光源所在平面相距59 cm的接收平面内,得到最大误差为2.05 cm、平均误差为8.64 mm的定位精度;使用正弦信号时,在与光源平面相距30 cm的接收平面内,得到最大误差为1.09 cm、平均误差为5.6mm的定位精度,并且使用交流信号时实验结果不受环境杂散光的干扰.     

三站时差频差定位精度分析

利用辐射源信号到达多个平台的到达时差信号和到达频差信号对辐射源进行定位,建立定位模型并计算几何精度因子(GDOP)。基于三站定位的平均处理方法,计算出GDOP 的合理区间。仿真结果表明:在GDOP 的合理区间,三站定位精度明显优于双站定位精度。     

大范围海域多站纯方位定位精度分布特性估计

针对大范围海域被动定位精度分布特性认识不足、制约测量系统优化设计的问题,提出一种基于多站纯方位定位体制的全区域精度特性估计方法,将定位求解、精度分析与布站优化集成考虑,采用非线性最小二乘法建立定位模型,应用Monte-Carlo方法建立随机误差传播算法,通过大样本、网格化仿真模拟得到全区域定位均方根误差(RMSE)分布。通过仿真验证,模型具有快速收敛特性,能够对测量元素变化产生合理响应,对于在30km×20km测量海区内采用5阵元星形布站、单站测向误差为2°~5°的场景,全区域RMSE中值达到1km精度水平。应用该方法能给出到全区域精度差异的细节特征,进而支持不同布站几何条件下的定位性能比对。仿真算例表明,在5阵元限定下,采用五边形布站能够获取比星形布站、矩形布站、梯形布站更优的精度分布,使区域内RMSE中值降低0.1km,同时高精度覆盖区明显扩大。该方法可为测量系统论证中的精度分析及布站优化设计提供技术途径。      

A Hybrid RF and Vision Aware Fusion Scheme for Multi-Sensor Wireless Capsule Endoscopic Localization

A huge torrent of data traffic is generated from various heterogeneous applications and services at the Internet backbone. In general, at the backbone, all such applications and services are allocated spectral resources under a shared spectrum environment within elastic optical networks (EONs). In such a fully shared environment, connection requests (CRs) belonging to different traffic profiles compete for spectral resources. Hence, it is very challenging for network operators to resolve resource conflict that occur at the time of provisioning resources to such CRs. The heterogeneous traffic profile (HTP) considered in this work includes permanent lightpath demands (PLDs) and scheduled lightpath demands (SLDs). We propose various distance adaptive routing and spectrum assignment (DA-RSA) heuristics to resolve resource conflict among these two traffic profiles in EONs under a full sharing environment. Conventionally, preemption was the only technique to resolve such resource conflict among HTPs. Since preemption involves the overhead of selecting CRs to be preempted and then deallocating the resources given to those CRs, excessive preemption adversely affects the performance of the network. Therefore, in this work, we utilized bandwidth splitting as a solution to resolve resource conflict among HTPs under such a shared environment in EONs. Moreover, an integrated solution consisting of splitting and preemption is also proposed. We refer to this new integration as flow-based preemption. Our simulation results demonstrate that bandwidth splitting-based heuristics yield significant improvement in terms of the amount of bandwidth accepted in the network, link and node utilization ratio, number of transponders utilized and the amount of bandwidth dropped due to preemption. Moreover, the flow-based preemption approach is proved to be superior in performance amongst all proposed strategies.

     

采用窄带特征提取方法提高声发射源定位精度

针对提高声发射源定位精度的需要,提出了利用小波变换从宽带非平稳声发射信号中提取稳定的窄带响应信息的方法,可降低环境噪声和波速色散效应的影响;进一步根据Hilbert变换提取窄带信号的包络,可根据第一个包络峰值正确判定应力波到达时刻.介绍了该方法的实现原理,组建了应力波源定位实验系统.采用十字定位法确定发射源位置.结果表明,采用新的窄带特征提取技术后,定位误差从原来的15 mm减少到4.9 mm.     

Compensation of RF impairment in multi-band receiver based on RF sub-sampling

This paper is studied about multi-band receiver using sub-sampling and time division multiplexing (TDM) techniques. Software defined radio (SDR) has a goal that places the analog to digital converter (ADC) as near the antenna as possible. But current technique actually cannot process ADC about radio frequency (RF) band signals. So one method is being studied that samples RF band signals to intermediate frequency (IF) band. As one of the ways, sub-sampling technique can convert signals from RF band to IF band without oscillator. If sub-sampling technique is used, over 2 bands can convert signals from RF band to IF band. However, due to the filter performance in RF band, it is possible that interference is generated between signals that are converted to low frequency band. And the problem degrades performance. In this paper, we propose one method that uses TDM technique as a solution to avoid interference between signals. By processing TDM and sub-sampling at the same time, the method can get signals without large changes from the conventional structures.     

射频集成电路发展趋势

据市场调研咨询公司In-Stat/MDR的研究者称,到2005年全球所有家庭和办公室的无线以太网(Wi-Fi)接入点将达4400百万个。.现有频带中消费电子设备信号的干扰日益增加。与日俱增的通信需求已给通信业提出了挑战。骨干网络的传输速度业已提升到万亿位每秒,光纤也正进入局域网和广域网。此外,第三代系统(3G)不久将取代两代半系统(2.5G),包括通用便携无线服务(GPRS)、乃至改进数据速率GSM服务(EDGE)。为进一步改善移动通话质量并能提供可视服务,选择适当的工艺技术将不像以往那样简单,设计者将要面对诸多的抉择。工艺技术以往,用于移动电…     

WSN射频芯片中6 GHz RF CMOS低功耗双模前置分频器的设计

介绍了一种可以应用在无线传感网射频芯片中的超高速、低功耗32/33双模前置分频器的内部结构、电路设计原理以及版图设计.该前置分频器采用0.18 μm RF CMOS工艺制作,工作频率范围为1～6 GHz,工作温度范围为-20～+80℃,在I.8 V电压下正常工作频率为4.8 GHz,最高工作频率达到6 GHz,电源电流为2.5 mA,满足系统指标要求.