Simulations and experiments for optimal deployment of an RFID‐based location‐aware system

The proliferation of communication and mobile computing devices and local‐area wireless networks has cultivated a growing interest in location‐aware systems and services. An essential problem in location‐aware computing is the determination of physical locations. RFID technologies are gaining much attention, as they are attractive solutions to indoor localization in many healthcare applications. In this paper, we propose a new indoor localization methodology that aims to deploying RFID technologies in achieving accurate location‐aware undertakings with real‐time computation. The proposed algorithm introduces means to improve the accuracy of the received RF signals. Optimal settings for the parameters in terms of reader and reference tag properties were investigated through simulations and experiments. The experimental results indicate that our indoor localization methodology is promising in applications that require fast installation, low cost and high accuracy. Copyright © 2009 John Wiley & Sons, Ltd.     

RFID-based localization with Non-Blocking tag scanning

The simple and cheap passive RFID tag systems have recently been used for efficient localization of indoor mobile robots, where each RFID tag stores its own absolute position and the mobile robot carrying an RFID reader scans the RFID tags to localize itself. The available localization schemes using passive RFID systems do not consider the scanning delay which may cause location estimation error, especially when the robot moves at a high speed. In this paper, a new Non-Blocking scanning (reading) scheme is proposed to avoid collisions so that the scanning delay, and consequently the localization error, can be reduced. This scheme avoids collisions among tag replies by assigning tag IDs based on the FCA coloring scheme. Theoretical and simulation studies indicate that the new Non-Blocking scheme combined with the new tag arrangement pattern can achieve a good RFID localization performance in terms of both estimation error and scanning delay with reduction of tag/reader required complexities.     

Integrating RFID and WLAN for indoor positioning and IP movement detection

Location awareness in an indoor environment and wireless access to Internet applications are major research areas towards the overwhelming success of wireless and mobile communications. However, the unpredictable indoor radio propagation and handover latency due to node mobility are the main challenging issues that need to be addressed. For tackling efficiently both problems of indoor localization and handover management, we propose combining key benefits of two outstanding wireless technologies, i.e. radio frequency identification (RFID) and a wireless local area network (WLAN) infrastructure. WLANs, such as IEEE 802.11 (WiFi), are now very common in many indoor environments for providing wireless communication among WiFi-enabled devices by accessing an Access Point (infrastructure mode) or through peer to peer connections (ad hoc mode). However, the small cell size of the Access Points (APs) in a WiFi-based network drives the need for frequent handovers leading to increased latency. RFID is an emerging technology consisting of two basic components, a tag and a reader, and its main purpose is the automatic identification of tagged objects by a reader. However, in the presence of multiple readers, RFID suffers from the so-called reader collision problem, mainly due to the inability for direct communication among them. In this paper, we propose a hybrid RFID and WLAN system; the RFID technology is employed for collecting information that is used for both localization and handover management within the WLAN, whereas the WLAN itself is utilized for controlling and coordinating the RFID reading process. In our system architecture, tag IDs of a RFID tag deployment are correlated with both location and topology information in order to determine the position and predict the next subnetwork of a Mobile Node (MN) with a reader attached to its mobile device. The role of the WLAN is to coordinate the readers when accessing the RFID channel for retrieving tags?? IDs, hence compensating the persisting RFID collision problem among multiple readers. Numerical results based on extensive simulations validate the efficiency of the proposed hybrid system in providing accurate and time efficient localization and reducing the IP handover latency.     

An adaptive location estimator using tracking algorithms for indoor WLANs

This paper presents adaptive algorithms for estimating the location of a mobile terminal (MT) based on radio propagation modeling (RPM), Kalman filtering (KF), and radio-frequency identification (RFID) assisting for indoor wireless local area networks (WLANs). The location of the MT of the extended KF positioning algorithm is extracted from the constant-speed trajectory and the radio propagation model. The observation information of the KF tracker is extracted from the empirical and RPM positioning methods. Specifically, a sensor-assisted method employs an RFID system to adapt the sequential selection cluster algorithm. As compared with the empirical method, not only can the RPM algorithm reduce the number of training data points and perform on-line calibration in the signal space, but the RPM and KF algorithms can alleviate the problem of aliasing. In addition, the KF tracker with the RFID-assisted scheme can calibrate the location estimation and improve the corner effect. Experimental results demonstrate that the proposed location-tracking algorithm using KF with the RFID-assisted scheme can achieve a high degree of location accuracy (i.e., more than 90% of the estimated positions have error distances of less than 2.1 m).     

An Efficient Anti-collision Protocol for Fast Identification of RFID Tags

Tag collision prevention/resolution for radio frequency identification (RFID) tags is one of the most significant issues for fast tag identification. This paper proposes a new anti-collision protocol that has objective of minimizing the tag identification delay. The proposed scheme reduces the tag collisions by allocating exclusive timeslot to each tag using identified timeslot information. Performance evaluation based on numerical and simulation results shows that the proposed anti-collision method improves RFID identification performance.     

基于牛顿插值的RFID室内定位算法

随着近年无线网络的发展,出现了多种与室内定位相关的技术与应用。文中提出了一种基于牛顿插值的室内定位算法。该算法主要是基于射频识别技术(RFID)并结合Larndmarc系统利用插值求解虚拟的标签,从而对待测标签得到更精确地定位。实验证明,与k邻域算法相比,该算法在定位精度上得到了显著提高。     

基于BP神经网络和泰勒级数的室内定位算法研究

 在研究分析室内无线信号传播特性和传统的室内定位算法的基础上,提出了用BP神经网络来拟合室内无线信号传播模型,避免了对无线信号传播模型中参数A和n的不精确估计.在训练完成的BP神经网络的输入层输入接收信号强度值RSSI(Received Signal Strength Indicator),在输出层即可得到对应的距离值,再利用泰勒级数展开法确定盲节点的坐标位置.最终通过Matlab仿真和ZigBee平台实验验证了算法的可行性和有效性.     

一种基于二维相控阵天线的RFID定位方法

RFID（Radio Frequency Identification）射频识别系统中,如何在识别标签基本信息的基础上进一步精准地感知标签的实时位置一直是一个重要问题.本文首次提出一种基于二维相控阵天线的非测距RFID标签定位方法（Phased Array based Range Free Tag Localization,PATL）.该方法利用相控阵天线辐射波束角度可调的特点,对搜索平面依次进行扫描,并通过统计不同天线区域内标签出现的次数,利用加权算法给出标签的二维位置.该方法能够在不借助参考标签或辅助设备的前提下对多个目标标签进行实时定位.通过利用一款集成有相控阵天线的商用超高频RFID阅读器对方法进行了实验验证.结果表明,算法的定位精度能达到21cm.     

Multiple feedback algorithm for RFID MAC protocols

This letter introduces a new tree-based anti-collision scheme using multiple feedbacks for uplink tag random access in a single-cell scenario. We examine MAC efficiency improvements that result from the proposed scheme in terms of uplink (UL) throughput for emerging radio frequency identification (RFID) networks, and compare it with the conventional tree based RFID MAC in ISO 18000-6 Type B standard.     

Performance Analysis of Tags Collection Time on A New Architecture of 2.4 GHz Embedded Active RFID System for Indoor and Outdoor Tracking and Monitoring Applications Based on IEEE 802.15.4 Standard

This paper focuses on the analysis of tags collection time of 2.4 GHz embedded active Radio Frequency Identification (RFID) system for indoor and outdoor real-time tracking and monitoring applications based on IEEE 802.15.4 standard. The main novelty of the system is the implementation of the communication method in order to provide Machine to Machine (M2M) communication and automated switching mechanism between indoor and outdoor location by utilizing active RFID, Wireless Sensor Network (WSN), Global Positioning System (GPS) and mobile communication on a single platform. In this work, GPS receiver covers outdoor location tracking, while active RFID provides identification and Receive Signal Strength Indicator (RSSI) reading for each tag holder to cover indoor location tracking especially near or inside building where location information is not detected by GPS. Several experiments were conducted on three different RFID tags which were active RFID tag embedded with GPS and GSM (ERFIDG2), active RFID tag embedded with GPS (ERFIDG) and standalone RFID tag communicating with the same active RFID reader. The experiment was done to evaluate the communication performance of the active RFID in terms of tags collection time using Transparent (AT) and Application Programming Interface (API) mode. The experiment was extended to measure tags collection time in single hop and multi hops communication for Tag Talk First (TTF) and Reader Talk First (RTF) protocols. The results show that the proposed active RFID system (ERFIDG2) is better than the standalone and ERFIDG systems. The in-depth research done in this work is to study the experience and identify the challenges that will be faced in the development and implementation of a wireless RFID-based system for tracking and monitoring applications.     

Improvement of the Hash-Based RFID Mutual Authentication Protocol

Radio frequency identification (RFID) is a popular kind of automatic identification technologies that uses radio frequencies. Many security and privacy problems my be raised in the using of RFID due to its radio transmission nature. In 2012, Cho et al. (Comput Math Appl, 2012. doi:10.1016/j.camwa.2012.02.025) proposed a new hash-based RFID mutual authentication protocol to solve these problems. However, this protocol was demonstrated to be vulnerable to DOS attack. This paper further shows that Cho et al.’s protocol is vulnerable to traffic analysis and tag/reader impersonation attacks. An improved protocol is also proposed which can prevent the said attacks.     

基于差分进化算法的RFID定位

针对传统射频识别(RFID)定位过程繁琐,系统定位精确度低以及计算较为复杂的问题,提出一种利用差分进化(DE)算法优化RFID定位精确度的方法。该方法首先随机初始参考标签的位置坐标,通过接收信号强度(RSS)值计算出阅读器与标签之间的测量距离,再通过优化阅读器与参考标签和待测标签之间的距离误差,估计出离待测标签最近的位置坐标,最后与经典LANDMARC定位系统做比较。仿真结果表明,经典LANDMARC定位系统的平均定位误差为1.115 8 m,而利用差分进化算法优化后的系统平均定位误差为0.001 2 m,从而证明利用差分进化算法优化RFID定位的方法是有效的。     

Server‐less RFID authentication and searching protocol with enhanced security

This paper focuses on two interesting radio‐frequency identification (RFID) cryptographic protocols: the server‐less RFID authentication protocol that allows readers to authenticate tags without the help of any online backend servers, and the RFID searching protocol in which the verifier explicitly specifies the target tag to be searched and authenticated. These two kinds of RFID protocols play important roles in many RFID applications; however, the existing protocols either had security weaknesses or exhibited poor efficiency. This paper shows the weaknesses, and then proposes our server‐less RFID authentication protocol and RFID searching protocol. The proposed protocols greatly enhance the security using one more hashing. Copyright © 2011 John Wiley & Sons, Ltd.     

An improved anti‐collision protocol for radio frequency identification tag

Many anti‐collision protocols have been proposed at present. Almost all known protocols exhibit an overall identification efficiency smaller than 50%. And all of them are proposed for general purpose applications and do not consider the distribution characteristic of tag IDs in different radio frequency identification (RFID) systems. In real world, there are many RFID systems, in which the tag IDs are mostly distributed continuously, such as in container terminals, warehouse management, supply chain management, and so on. This paper presents an efficient anti‐collision protocol, named improved collision tree protocol (ICT), to identify RFID tags simultaneously. The main novelties of this paper include that the duality and certainty principle is introduced and used in ICT to improve the tag identification efficiency, and the continuous and partially continuous distributions of tag IDs are taken into account in this paper. Both the theoretical and experimental results indicate that ICT improves the tag identification efficiency up to 100% when the tag IDs are distributed continuously, and always above 50% even when the tag IDs are distributed uniformly. For straightforward and efficient, ICT can be used in various RFID tag identification conditions, especially when the tag IDs are distributed continuously or partially continuously. Copyright © 2013 John Wiley & Sons, Ltd.     

A Polygonal Method for Ranging-Based Localization in an Indoor Wireless Sensor Network

In this paper, we propose an indoor localization method in a wireless sensor network based on IEEE 802.15.4 specification. The proposed method follows a ranging-based approach using not only the measurements of received signal strength (RSS) but also the coordinates of the anchor points (APs). The localization accuracy depends on the errors in the distance estimation with the RSS measurements and the size of the polygon composed of the APs used for the lateration. Since errors are inevitably involved in the RSS measurement, we focus on reducing the size of the polygon to increase the localization accuracy. We use the centroid of the polygon as a reference point to estimate the relative location of a target in the polygon composed of the APs hearing the target. Once the relative position is estimated, only the APs covering the area are used for localization. We implement the localization method and evaluate the accuracy of the proposed method in various radio propagation environments. The experimental results show that the proposed method improves the localization accuracy and is robust against the dynamically changing radio propagation environments over time.     

A fast tag identification anti‐collision algorithm for RFID systems

In this work, we propose a highly efficient binary tree‐based anti‐collision algorithm for radio frequency identification (RFID) tag identification. The proposed binary splitting modified dynamic tree (BS‐MDT) algorithm employs a binary splitting tree to achieve accurate tag estimation and a modified dynamic tree algorithm for rapid tag identification. We mathematically evaluate the performance of the BS‐MDT algorithm in terms of the system efficiency and the time system efficiency based on the ISO/IEC 18000‐6 Type B standard. The derived mathematical model is validated using computer simulations. Numerical results show that the proposed BS‐MDT algorithm can provide the system efficiency of 46% and time system efficiency of 74%, outperforming all other well‐performed algorithms.     

一种低功耗有源射频识别系统的设计

研究了一种低功耗有源射频识别系统组网与设计技术,该系统可在软硬件两方面实现低功耗设计。在硬件方面,采用NORDIC公司的nRF24LE1芯片作为有源标签,nRF24L01+芯片作为节点射频芯片,STM32单片机作为节点控制芯片,实现了芯片与节点的注册与通信;软件方面,采用时分复用方法,合理分配有源芯片的时隙,设计了防冲突机制,使得芯片在极端的时间内工作,实现了低功耗组网通信。     

Mobile location estimation for DS‐CDMA systems using self‐organizing maps

In this paper, a self‐organizing map (SOM) scheme for mobile location estimation in a direct‐sequence code division multiple access (DS‐CDMA) system is proposed. As a feedforward neural network with unsupervised or supervised and competitive learning algorithm, the proposed scheme generates a number of virtual neurons over the area covered by the corresponding base stations (BSs) and performs non‐linear mapping between the measured pilot signal strengths from nearby BSs and the user's location. After the training is finished, the location estimation procedure searches for the virtual sensor which has the minimum distance in the signal space with the estimated mobile user. Analytical results on accuracy and measurement reliability show that the proposed scheme has the advantages of robustness and scalability, and is easy for training and implementation. In addition, the scheme exhibits superior performance in the non‐line‐of‐sight (NLOS) situation. Numerical results under various terrestrial environments are presented to demonstrate the feasibility of the proposed SOM scheme. Copyright © 2006 John Wiley & Sons, Ltd.     

Hardware implementation of tag-reader mutual authentication protocol for RFID systems

Radio-frequency identification (RFID) is a recent technology that utilizes radio frequencies to track the object by transmitting a signal with a unique serial identity. Generally, the drawbacks of RFID technology are high cost and authentication systems between a reader and a tag become weak. In this paper, we proposed a protocol for RFID tag–reader mutual authentication scheme which is hardware efficient and consumes less dynamic power. Truncated multipliers are implemented in RFID tag–reader mutual authentication protocol system due to reduction in hardware cost and dynamic power. Experimental evaluation reveals that the proposed protocol with truncated multipliers provides more security than the earlier schemes. The proposed protocol is described in VHDL and simulated using Altera Quartus II. The functional block is implemented as hardware using an Altera DE2 Cyclone II (EP2C35F672C6) Field-Programmable Gate Array (FPGA).     

RFID系统中面向服务的动态资源配置优化机制

针对物联网中RFID(radio frequency identification)系统的tag和reader的速率不匹配及其资源受限问题,从理论上对tag和reader之间的协作通信上下文进行分析,提出一种面向服务的RFID系统资源配置优化机制,该机制利用tag与reader的组件QoS(quality of service)信息建立闭环控制框架,使用3种控制策略根据其资源状态和类型调节QoS参数。通过实验对机制进行了性能分析和验证,结果表明,该优化机制有效地提高RFID系统的吞吐量,高效地使用系统资源,减少了能量消耗和reader-to-reader干扰。