位屏蔽多叉树搜索射频识别防碰撞算法

针对RFID树型防碰撞算法中时隙数多、数据通行量大等问题,提出了一种改进的多叉树防碰撞算法,阅读器准确检测碰撞位并向标签反馈碰撞位信息,标签对阅读器已知的ID位进行屏蔽,把ID号转换成连续碰撞的序列号.阅读器利用屏蔽位信息和标签返回的碰撞位编码信息,对标签进行分层分类搜索.通过对标签ID进行屏蔽,阅读器和标签间仅发送对方不知道的碰撞位信息.该算法减少了碰撞时隙和识别时隙,避免了空闲时隙,减少了阅读器和标签间的数据通信量.理论分析和仿真结果表明,该算法减少了系统的时隙总数和数据通信量,提高了阅读器的识别效率.     

基于软件无线电的RFID阅读器设计

针对目前RFID系统工作频率多样,各类标准众多且差距较大,不适合多种标签同时应用的情况,提出了基于软件无线电及LabVIEW设计RFID阅读器的思想.通过加载不同的软件代码,仿真阅读器可以实现对不同频段,符合不同标准的RFID标签进行读写.通过与标准阅读器的读取结果进行比对,仿真阅读器实现了对RFID标签携带信息的读取,节约了需要配置各种不同类型阅读器的成本.     

基于位判别的后退式搜索防碰撞算法

在射频识别(RFID)系统中,经常出现多个标签同时向阅读器传递信息,进而相互干扰导致阅读器无法正确识别标签的碰撞现象。针对这一问题,提出了一种基于位判别的后退式二进制搜索防碰撞算法。该算法在传统后退式二进制搜索算法的基础上进行了改进,提出了碰撞距离的概念,通过对碰撞距离的判别来确定搜索的方式。实验结果表明,改进算法的性能比其他几种算法有所提高,传送数据量降低了很多。该算法可以有效的减少传输数据量,提高识别速率。     

基于RFID技术的自适应分组标签防碰撞算法研究

RFID技术具有安全可靠、可远距离识别等特点,被广泛应用于智能识别与机器人技术中。传统的类标签算法普遍存在不足,文中基于RFID技术研究了自适应分组的标签防碰撞算法。自适应分组的标签防碰撞算法在一定程度上改善了多目标标签的情形,提高了系统的识别速度,且利用了阅读器与标签中的信息通道。仿真结果表明,自适应分组标签防碰撞算法可以大幅减少能量损耗,提高识别精度,弥补了传统算法的不足。     

分组自适应分配时隙的RFID防碰撞算法研究

为了解决射频识别(Radio Frequency IDentification,RFID)系统中的多标签防碰撞问题,在分析帧时隙ALOHA算法的基础上,提出一种基于分组自适应分配时隙的RFID防碰撞算法(GAAS).首先让阅读器对标签随机所选的时隙进行扫描统计,并将其发送给每一个标签,标签再进行相应地时隙调整,使阅读器跳过空闲时隙和碰撞时隙,自适应地分配有效时隙,进而对标签进行快速识别.当未识别标签数比较大时,算法采用分组以及动态调整帧长等策略,以减少时隙处理的时间.仿真结果表明:GAAS算法提高了系统的识别效率和稳定性,降低了传输开销.特别是当标签数超过1000时,该算法的吞吐率仍保持在71%以上,比传统的帧时隙ALOHA-256算法和分组动态帧时隙ALOHA算法的系统效率分别提高了300%和97.2%.     

一种改进的RFID防碰撞算法

在RFID系统中,当多个标签同时处在阅读器的读写范围内时,如果没有相应的防冲突机制,会导致标签到阅读器的通信冲突,使得从标签返吲的数据难以被阅读器正确识别.防冲突算法是阅读器快速、正确获取标签数据的关键.详细论述了射频识别技术中的关键问题:防碰撞技术,提出了一种基于二进制防碰撞算法的改进树形算法.在介绍Manchester编码原理的基础上,对该改进算法的命令、原理进行了较为系统的论述,经验证该算法提高了阅读器辨认标签的速度,辨认准确性也大大提高,在电子标签数量较大的情况下比传统的二进制及动态二进制防碰撞算法优势更加明显.     

基于无源标签的远距离射频识别系统

通过RFID阅读器将标签对标签中的信息进行收集,然后将信息传送到操作应用系统中去,从而得知标签内容。虽然有源标签的传输距离要大于无源标签,但是考虑到设计成本及系统的广泛使用,于是文中通过标签依靠阅读器发送过来的载波将存储的信息发送到阅读器,再由内嵌在阅读器中的ZigBee,传送给作为协调器的ZigBee模块后送往应用系统中去,通过无源RFID和ZigBee来建立远距离的模型,达到扩大射频覆盖范围的功能。     

高级RFID阅读器应用对处理器的要求

射频识别（RFID）技术平稳地渗透到我们日常生活的许多方面。从超市的库存管理到快速收款，这项技术正改变着许多现有的应用并支持新的应用。在RFID前端，“信号链”从有效装置上的小标签开始，将信息、传送给一个或多个RFID阅读器，当标签出现在特定的区域内时，阅读器检测。在RFID后端，基于服务器的系统保持并更新标签数据库。RFID系统框图如图1所示。     

双时隙动态二进制搜索RFID防碰撞算法

在二进制搜索算法的基础上引入时隙的思想,提出了一种新的防碰撞算法:双时隙动态二进制搜索防碰撞算法.该算法利用阅读器堆栈形成进一步搜索命令;响应标签分为两个子集,并分别在两个时隙发送数据信息,一次搜索最多可识别4个标签.仿真结果表明:新算法减少了搜索次数和识别时间,提高了RFID系统的性能.     

一种具有阅读器匿名功能的射频识别认证协议

在射频识别(RFID)的应用中,安全问题特别是用户隐私问题正日益凸显。因此,(用户)标签信息的隐私保护的需求越来越迫切。在RFID系统中,标签的隐私保护不仅是对外部攻击者,也应该包括阅读器。而现有许多文献提出的认证协议的安全仅针对外部攻击者,甚至在外部攻击者的不同攻击方法下也并不能完全保证安全。该文提出两个标签对阅读器匿名的认证协议：列表式RFID认证协议和密钥更新式RFID认证协议。这两个协议保证了阅读器对标签认证时,标签的信息不仅对外部攻击者是安全的而且对阅读器也保持匿名和不可追踪。相较于Armknecht等人提出的对阅读器匿名和不可追踪的认证协议,该文所提的协议不再需要增加第三方帮助来完成认证。并且密钥更新式RFID匿名认证协议还保证了撤销后的标签对阅读器也是匿名性和不可追踪的。     

An Efficient Reader Anticollision Algorithm in Dense RFID Networks With Mobile RFID Readers

In parallel with the proliferation of radio-frequency identification (RFID) systems, many RFID readers have been increasingly employed. In such an environment, collision among readers becomes a serious problem. Existing anticollision algorithms, depending on the information of neighboring readers, may require constant effort in order to grasp such information. Although it may be given by a server or a coordinator, they may not be suitable in dense and dynamic RFID networks with mobile readers. In this paper, we propose an efficient reader anticollision algorithm using a polling server in dense and dynamic RFID networks with mobile readers. Owing to the assistance of the server, the readers can rapidly decide whether they can work or not without interfering neighbors and can be easily synchronized. Our proposed algorithm is simple and makes readers aware of neighbors to minimize reader collisions. Performance evaluation shows how many readers can operate in a network and indicates that our proposed algorithm is more efficient than distributed color selection, colorwave, and hierarchical Q-learning algorithm, particularly in dense and mobile environments.      

基于低级别读写器协议的无线射频识别中间件系统

无线射频识别（RFID）技术的应用在近年来取得了长足的发展。RFID中间件系统是RFID网络的重要组成部分,位于RFID应用系统和RFID读写器之间,是RFID标签信息的处理中枢。传统的RFID中间件系统对上层的RFID应用系统提供了统一的应用层事件（ALE）接口,但是和RFID读写器之间的连接则采用适配读写器厂商私有接口的方式,不利于快速构建RFID应用系统。基于低级别读写器协议（LLRP）的RFID中间件系统提供了标准的接口来接入不同厂商的读写器,大幅度地提高了构建RFID应用系统的效率。     

A self learned invasive weed-mixed biogeography based optimization algorithm for RFID network planning

The optimal placement of the RFID readers inaugurates an ongoing research field, namely the RFID network planning (RNP). The main issue in the RNP is to know how many readers have to be used and what is their best distribution that guarantees fulfillment of multiple objectives. The common RNP objectives are the optimal coverage, readers’ interference avoidance, redundant reader elimination, load balance among deployed readers and minimum power losses, which are considered as conflicting objectives that leads the RNP to be an NP-hard problem need to be solved. The contributions in this paper are: firstly, utilizing both the Biogeography based optimization (BBO) and the Hybrid Invasive Weed-Biogeography based optimization (HIW-BBO) as new algorithms have not used before for solving the RNP. Secondly, we proposed a Self Learning (SL) strategy with a mixed BBO Migration (MBBOM) operation to modify the HIW-BBO algorithm in an algorithm called Self Learned Invasive Weed-Mixed Biogeography based optimization (SLIWMBBO). Thirdly, the performance of the proposed SLIWMBBO algorithm is compared to both the HIW-BBO and the Self Adaptive Cuckoo Search (SACS) optimization algorithms according to a set of 13 benchmark functions. The results of this comparison encourage the application of the SLIWMBBO as an optimization algorithm for solving the complex problems. Lastly, the BBO, HIW-BBO and SLIWMBBO optimization algorithms are used for solving three complex RNP instances and compared to the SACS algorithm. Simulation results of the SLIWMBBO are outstanding and demonstrate its superiority over the compared algorithms.

     

基于寄生振子的多频印刷天线

RFID技术近年来发展迅猛,但是各国使用的频段却不统一。为了增强RFID系统的兼容性,本文设计一款应用于RFID标签的3频印刷天线。采用加载寄生振子实现天线的3频工作。使用ADS仿真软件对本文所设计的天线进行了仿真研究,结果表明反射损耗小于-15dB时天线的工作带宽分别为782.5～851.1MHz,919.3～995.5MHz,2.446～2.577GHz,满足设计要求。这3个频段分别覆盖了中国划分的两个RFID频段以及国际通用的2.45GHz频段。     

Radio frequency identification: technologies,applications, and research issues

A radio frequency identification (RFID) system is a special kind of sensor network to identify an object or a person using radio frequency transmission. A typical RFID system includes transponders (tags) and interrogators (readers): tags are attached to objects/persons, and readers communicate with the tags in their transmission ranges via radio signals. RFID systems have been gaining more and more popularity in areas such as supply chain management, automated identification systems, and any place requiring identifications of products or people. RFID technology is better than barcode in many ways, and may totally replace barcode in the future if certain technologies can be achieved such as low cost and protection of personal privacy. This paper provides a technology survey of RFID systems and various RFID applications. We also discuss five critical research issues: cost control, energy efficiency, privacy issue, multiple readers' interference, and security issue. Copyright © 2006 John Wiley & Sons, Ltd.     

Low Access Delay Anti-Collision Algorithm for Readers in Passive RFID Systems

Even though radio frequency identification (RFID) systems are spreading more and more as a medium for identification, location and tracking purposes, some reliability issues of these systems still need to be solved. In fact, RFID readers and tags experience collisions when sharing the wireless transmission channel over the same area. In this work, we propose a centralized scheduling-based algorithm as possible candidate solution for the reader collision problem in passive RFID systems. This algorithm has been designed taking into account the circuitry limitations of the tags, which do not allow the usage of frequency or code division multiple access schemes in passive RFID systems. The solution herewith proposed, which is suitable for those scenarios involving static or low mobility readers, aims at preventing reader collisions and provides at the same time low channel access delay to the readers. The performance of this algorithm has been tested via computer simulations. The results show that the proposed solution strongly reduces collision occurrences and, especially in static scenarios, provides low access delay to the readers during the channel contention phase.     

Network Information Security Data Protection Based on Data Encryption Technology

Today Radio Frequency Identification systems (RFID) are one of the most usable automated wireless identification technologies in the internet of things. Identification systems can exchange data remotely by communicating between a tag and a reader with sending radio waves. The main challenge of identification systems with radiofrequency in a dense RFID network is the collision, which occurs when readers are located in each other's interference range and start reading tags simultaneously. With these collisions happening, readers cannot read all the tags around them in the efficient time durations. In this research, using a distributed method and the channel listening technique, readers select a time interval to take the control channel by the Geometric Probability Distribution Function. Also, by measuring the signal strength from neighboring readers and sharing tag information, there will be an increase in the throughput of identification systems through radio waves while avoiding all kinds of collisions in the control channel. Extensive results show that the proposed method has better throughput and has less average waiting time.

     

Public key cryptography based privacy preserving multi-context RFID infrastructure

In this paper, we propose a novel radio frequency identification (RFID) infrastructure enabling multi-purpose RFID tags realized by the use of privacy preserving public key cryptography (PKC) architecture. The infrastructure ensures that the access rights of the tags are preserved based on the spatial and temporal information collected from the RFID readers. We demonstrate that the proposed scheme is secure with respect to cryptanalytic, impersonation, tracking, replay, and relay attacks. We also analyze the feasibility of PKC implementation on passive class 2 RFID tags, and show that the requirements for PKC are comparable to those of other cryptographic implementations based on symmetric ciphers. Our numerical results indicate PKC based systems can outperform symmetric cipher based systems, since the back end servers can identify RFID tags with PKC based systems approximately 57 times faster than the best symmetric cipher based systems.     

Tracking via Square Grid of RFID Reader Positioning and Diffusion Algorithm

The study and analysis of RFID (radio frequency identification) reader positioning is important for RFID large-scale deployment. Therefore, the purpose of this research is to investigate the art of RFID reader positioning in order to develop a highly accurate positioning and tracking system for usage inside a building and also to optimize the tracking performance that can be applied to different active and passive RFID standards. This study involves design of square grid RFID reader network and position calculation using diffusion algorithm. Square grid network presents the solution of placement pattern of RFID readers, hence optimal number of required readers and guaranteed coverage can be achieved. The proposed diffusion algorithm makes use of distance information between the reader and the tag to estimate the RFID tag position. This study has also introduced a probabilistic mathematical model to maintain coverage of the unit square region and to ensure connectivity of the proposed square grid network. The effectiveness of the diffusion algorithm is evaluated in this study and the obtained results show satisfactory performance. The obtained results show that the proposed positioning system can achieve average positioning error below 1 m with different RFID reading ranges and in some cases accuracy improvement of about 65% can be reached than the results obtained by known positioning system. It is also found that the proposed diffusion algorithm together with square grid can bring approximately 50–85% improvement on raw accuracy provided by only square grid method.     

An efficient resource allocation scheme in a dense RFID network based on cellular learning automata

Radio‐frequency identification (RFID) is a wireless communication technology. Radio frequencies can cause interference in a dense RFID system, thus decreasing efficiency. In recent years, many protocols have been proposed to reduce reader collisions based on multiple‐access techniques. The main weakness of Time Division Multiple Access (TDMA)‐based schemes is the random selection of resources. Additionally, they do not consider the distance between the interfering readers. Therefore, the likelihood of interference in an RFID system will be increased. To address this problem, we propose a new scheme for allocating resources to readers using a learning technique. The proposed scheme takes into account the distance between interfering readers, and these readers acquire the necessary knowledge to select new resources based on the results of the previous selection of neighboring readers using cellular learning automata. This approach leads to reduced interference in an RFID system. The proposed scheme is fully distributed and operates without hardware redundancy. In this scheme, the readers select new resources without exchanging information with each other. The simulation results show that the percentage of kicked readers decreased by more than 20%, and the proposed scheme also provides higher throughput than do state‐of‐the‐art schemes for dense reader environments and leads to further recognition of tags.