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.     

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.     

A New Privacy Aware Payment Scheme for Wireless Charging of Electric Vehicles

Electric vehicles (EVs) can be considered as a revolution in the combustion industry with significant improvement in fuel utilization and decrease in pollution compared to combustion engines. However, by decreasing the size of the battery to reduce the cost, the frequency of charging EVs in a day increases. Therefore, to reduce the downtime required for charging EVs, wireless charging on the move can be an effective solution. In such a situation, paying for wireless charging on the move is an important issue. However, it can endanger the location privacy of users, since the EVs need to charge frequently in a day. In this paper, we first explain different methods of payment and problems with such payment methods in the case of wireless charging on the move. Then, we propose an efficient payment method based on ‘tokens’ for wireless charging on the move, which minimizes the communications between service providers and users during the charging process. The proposed scheme prevents users and service providers from cheating, and it is robust to support different values for the price. Finally, we compare it with other payment methods that have been proposed for plug-in electric vehicles.     

A Distributed Node Localization Scheme for Wireless Sensor Networks

A distributed node localization scheme for wireless sensor networks (WSNs) is presented in this paper, and it includes three generic phases: (1) determine node-beacon distances, (2) compute node positions, and (3) refine the positions. Different from previous researches, we propose an algorithm combination Min–max + LI for the position derivation and SD method for the refinement in our scheme. Simulation shows that our proposed scheme can perform more robust than some representative distributed node localization schemes presented in previous researches in terms of the trade-off among accuracy, coverage, computation cost, and communication overhead.     

On Data Fusion for Parametric-Model-Based Wireless Localization

In this paper, we present a data fusion framework for parametric-model-based wireless localization where the mobile station location is treated as a deterministic unknown vector. Three types of fusion schemes are presented: measurement fusion, estimate fusion and mixed fusion. Theoretical performance comparison among these schemes in terms of the estimation root mean square error via the weighted least square estimator (WLSE) is conducted. Such a performance metric coincides with the Cramer-Rao lower bound (CRLB) in the case of Gaussian noise. We show that, if the raw measurement vectors are correlated, then measurement fusion achieves the best performance, mixed fusion follows and estimate fusion is the worst. If the raw measurement vectors are uncorrelated, then these different fusion schemes achieve the same performance. Benefits that can be earned from data fusion for wireless localization are also investigated and numerical examples are presented to validate our theoretical analysis.     

A Hybrid Trust Management Scheme for Wireless Sensor Networks

Wireless sensor network (WSN) consists of wireless small sensor nodes deployed in the terrain for continuous observation of physical or environmental conditions. The data collected from the WSN is used for making decisions. The condition for making critical decision is to assure the trustworthiness of the data generated from sensor nodes. However, the approaches for scoring the sensed data alone is not enough in WSN since there is an interdependency between node and data item. If the overall trust score of the network is based on one trust component, then the network might be misguided. In this work, we propose the hybrid approach to address the issue by assigning the trust score to data items and sensor nodes based on data quality and communication trust respectively. The proposed hybrid trust management scheme (HTMS) detects the data fault with the help of temporal and spatial correlations. The correlation metric and provenance data are used to score the sensed data. The data trust score is utilized for making decision. The communication trust and provenance data are used to evaluate the trust score of intermediate nodes and source node. If the data item is reliable enough to make critical decisions, a reward is given by means of adding trust score to the intermediate nodes and source node. A punishment is given by reducing the trust score of the source and intermediate nodes, if the data item is not reliable enough to make critical decisions. Result shows that the proposed HTMS detects the malicious, faulty, selfish node and untrustworthy data.     

A Low-Power Digital IC Design Inside the Wireless Endoscopic Capsule

This paper proposes an architecture of the wireless endoscopy system for the diagnoses of whole human digestive tract and real-time endoscopic image monitoring. The low-power digital IC design inside the wireless endoscopic capsule is discussed in detail. A very large scale integration (VLSI) architecture of three-stage clock management is applied, which can save 46% power inside the capsule compared with the design without such a low-power design. A stoppable ring crystal oscillator with minimal overhead is used in the sleep mode, which results in about 60-muW system power dissipation in sleep mode. A new image compression algorithm based on Bayer image format and its corresponding VLSI architecture are both proposed for low-power, high-data volume. Thus, 8 frames per second with 320*288 pixels can be transmitted with 2 Mb/s. The digital IC design also assures that the capsule has many flexible and useful functions for clinical application. The digital circuits were verified on field-programmable gate arrays and have been implemented in 0.18-mum CMOS process with 6.2 mW     

Non-parametric Method of Path Loss Estimation for Endoscopic Capsule Localization

Localization of the wireless video capsule endoscope (VCE) is necessary for proper diagnosis and treatment of the lesions in the gastrointestinal tract. In this paper, we propose path loss based VCE localization algorithm using weighted average of the sensors position. The main challenge in path loss based localization in human body is the scattered random deviation of path loss caused by the shadowing and multipath propagation of non-homogeneous medium. To address the randomness issue of the scattered path loss, we propose three non-parametric methods of path loss estimation using moving averaging, local weighted regression and local Gaussian weighted average. Then we use the degree based estimated path loss to calculate the weight of the sensors position. We propose a heuristic method of degree estimation for the estimated path loss. We develop a simulation platform using MATLAB to evaluate the performance of our proposed methods. The results show significant improvement in accuracy without any prior knowledge of distance related channel parameters.     

A Distributed Localization Scheme for Wireless Sensor Networks with Improved Grid-Scan and Vector-Based Refinement

Localization is a fundamental and essential issue for wireless sensor networks (WSNs). Existing localization algorithms can be categorized as either range-based or range-free schemes. Range-based schemes are not suitable for WSNs because of their irregularity of radio propagation and their cost of additional devices. In contrast, range-free schemes do not need to use received signal strength to estimate distances and only need simple and cheap hardware, and are thus more suitable for WSNs. However, existing range-free schemes are too costly and not accurate enough or are not scalable. To improve previous work, we present a fully distributed range-free localization scheme for WSNs. We assume that only a few sensor nodes, called anchors, know their locations, and the remaining (normal) nodes need to estimate their own locations by gathering nearby neighboring information. We propose an improved grid-scan algorithm to find the estimated locations of the normal nodes. Furthermore, we derive a vector-based refinement scheme to improve the accuracy of the estimated locations. Analysis, simulation, and experiment results show that our scheme outperforms the other range-free schemes even when the communication radius is irregular.     

一种基于球面坐标的无线传感器网络三维定位机制

 节点定位作为无线传感器网络应用支撑技术之一,一直备受学术界和工业界的关注.现有的大多数定位算法针对平面应用而设计,无法满足三维空间应用.针对目前三维空间定位算法的不足,本文提出了一种基于球面坐标的动态定位机制,将定位问题抽象为多元线性方程组求解问题,最终利用克莱姆法则解决多解、无解问题.仿真结果表明,当在100*100*100m³的仿真场景内部署100个传感器节点,通信半径为10m、锚节点密度为10%时,相对定位误差为50.7%.在算法中引入了最小二乘法理论来估算节点位置以及结果过滤策略以减小定位误差,试验结果表明,改进后的算法性能提高了32.2%.     

Energy Proficient Hybrid Secure Scheme for Wireless Sensor Networks

Wireless Personal Communications - One way hash chain with a new key indicating the performance of the node as well to isolate malicious nodes from the network. Public key cryptography is derived...     

An Interactive and Energy-efficient Node Localization Scheme for Wireless Sensor Networks

How to obtain accurate position of sensor node is still a challenging problem for wireless sensor networks (WSNs). This work concentrates on the problem of node localization with mobile anchor node, which is applied to broadcast beacon packets in the region of interest (ROI). Node localization scheme SAA-ERL (speed adaptive adjustment-energy ratio localization) for WSNs is realized in way of interactive communications. SAA scheme determines the suitable moving speed and direction for the mobile anchor node, while the ERL mechanism generates virtual hyper-spheres to help unknown nodes acquire their locations. Based on the quantitative analysis of the localizing performances, the guidelines for system parameters are obtained. Simulation results validate that when system parameters are jointly designed, SAA-ERL can be adapted to scenarios of diversified applications.     

一种基于相似度的无线异构网络遗传定位方法

定位技术是无线异构网络的关键技术之一,目标跟踪、辅助路由、网络管理等诸多网络功能的实现都依赖于对目标位置的准确定位.本文研究单基站WCDMA与WLAN构成的异构网络中节点定位问题,通过引入相似度确定初始种群,提出一种基于遗传算法的无线异构网络定位方法.算法利用WCDMA基站存在视距路线时的高精度TOA测距值,并采用了相似度的分析手段,对遗传算法中的初始群体进行选择.仿真结果表明,由于综合了两个网络的测距信息,且同时采用TOA测距值和相似度来确定初始群体,算法定位精度较高.     

基于IMU/视觉融合的导航定位算法研究

针对基于视觉传感器的移动机器人在快速运动或发生旋转时出现图像模糊和特征丢失,以至无法进行特征匹配,从而导致系统定位和建图的准确度及精确度下降问题,该文提出了一种以深度相机(RGB_D)融合惯性测量单元(IMU)的方案。采用ORB SLAM2算法进行位姿估计,同时将IMU信息作为约束弥补相机数据的缺失。两种传感器的测量数据采用基于扩展卡尔曼滤波的松耦合方式进行非线性优化,通过数据采集实验表明,该方法能有效提高机器人的定位精度和系统建图效果。     

Paired Measurement Localization: A Robust Approach for Wireless Localization

Location awareness remains the key for many potential future applications of distributed wireless ad hoc sensor networks (WSNs). While the location of a WSN node can be estimated by incorporating Global Positioning System (GPS) devices, it is not suitable to embed GPS receivers in every node considering the cost and size of these devices as well as from an optimization point of view. However, a small number of WSNs nodes called anchor nodes are able to resolve their location either through fixed deployment or using GPS receivers, and thereby provide the reference framework for localization of other nodes. The measurement devices in individual nodes are often erroneous for tiny WSNs nodes, and hence, robustness is a major issue for localization. In this paper, a theoretical localization framework in the presence of noise is postulated, which achieves accurate positioning compared to the existing theoretical approaches. The paired measurement localization (PML) strategy is evaluated through simulations under various noise conditions and environmental modeling, and practically verified by a testbed implementation with real motes. The results corroborate the improved positioning as well as the robustness of PML for ad hoc wireless sensor networks in the presence of noise.     

多传感器数据融合评估系统的设计与实现

多传感器数据融合技术现已成为研究热点,但对它的研究往往缺乏必要的仿真手段和评估手段。为不断验证和改进融合系统的融合算法,设计并实现了一个多传感器数据融合评估系统：首先建立了评估系统的模型;接着对评估指标,按精度、相关性和处理能力三方面内容,给出了详细定义和计算方法;并针对评估实现中的关键问题,给出了基于最近邻域的相关技术、基于自适应均值门限判断的正确航迹判断技术和基于Matlab的可移植编程技术等解决方法。仿真实验表明,评估指标设计合理,评估系统切实可用。     

Hybrid Wireless Sensors Deployment Scheme with Connectivity and Coverage Maintaining in Wireless Sensor Networks

With the rapid growth of the internet of things (IoT), an impressive number of IoT’s application based on wireless sensor networks (WSNs) has been deployed in various domain. Due to its wide ranged applications, WSNs that have the capability to monitor a given sensing field, became the most used platform of IoT. Therefore, coverage becomes one of the most important challenge of WSNs. The search for better positions to assign to the sensors in order to control each point of an area of interest and the collection of data from sensors are major concerns in WSNs. This work addresses these problems by providing a hybrid approach that ensures sensors deployment on a grid for targets coverage while taking into account connectivity. The proposed sequential hybrid approach is based on three algorithms. The first places the sensors so as to all targets are covered. The second removes redundancies from the placement algorithm to reduce the number of sensors deployed. The third one, based on the genetic algorithm, aims to generate a connected graph which provide a minimal path that links deployed sensors and sink. Simulations and a comparative study were carried out to prove the relevance of the proposed method.

     

无线内窥镜专用芯片的FPGA验证及相关测试

介绍了一种数字式无线内窥镜的系统方案及其胶出并实现了用于该数模混合专用芯片的FPGA验证系统及验证流程.为了进行芯片系统级低功耗设计,验证系统完成了体内硬件部分的能量测试.