按需时隙分配RFID防碰撞协议研究

为进一步提高射频识别阅读器的标签识别效率,提出一种按需时隙分配高效防碰撞协议.该协议将识别循环分为预约帧时隙阶段和在帧时隙内读取标签两个阶段,通过帧前预约机制消除读取阶段的空闲时隙,采用预约冲突捕获机制有效地减少了读取阶段的碰撞时隙数.在此基础上,通过选择最优预约时隙随机码位数和最优预约时隙数,实现了该防碰撞协议的识别效率最优化,分析了该协议标签电路复杂性,并给出了适用于本协议的标签数估计方法.性能评估表明:该防碰撞协议的平均识别效率达到91.28%,在通信复杂性和识别速度方面明显优于现有典型防碰撞协议.     

物理层超高频射频识别标签信号分离中的信道估计

在被动式的超高频(UHF)射频识别(RFID)系统中,当多个标签选择同一个时隙向阅读器发送信息,标签间冲突就会产生,该冲突通常只在介质访问控制(MAC)层上解决。其实,若冲突信号在物理层上被分离,识别效率将能得到很大的提高。在物理层冲突信号分离中,信道估计是一项关键技术,因为好的信道估计有助于准确地恢复冲突信号。传统的信道估计方法在两个标签冲突的情况下具有较好的估计性能,但当冲突标签数超过2时,却会产生较高的误差。该文针对物理层的UHF RFID信号分离问题,提出一种新的信道估计方法。该方法利用已知的前缀信号,采用最小二乘方法对信道进行估计。从实验结果看,当标签冲突数超过2时,该文提出的信道估计方法的误差要小于传统的估计方法,而且估计的信道得到的分离效率也高于传统方法。     

基于CDMA和动态时隙ALOHA的UHF RFID防碰撞研究

为提高UHF RFID系统防碰撞性能,提出了一种基于码分多址(CDMA)和动态时隙ALOHA相结合的超高频RFID无源标签防碰撞识别方案。设计了标签防碰撞性能评估方案,采用Matlab进行仿真分析。性能分析和仿真结果显示,该方案在尽可能降低标签硬件复杂度和功耗的前提下,充分利用了码分多址和动态时隙ALOHA的性能,允许多个标签同时发送数据,提高了标签的识别速率。     

改进的基于ALOHA的RFID防碰撞算法

为了解决RFID系统中电子标签识别效率不高的问题,对基于ALOHA的随机性防碰撞算法进行了详细分析,提出了一种新的ALOHA防碰撞算法.在该算法中,针对标签估计,采用动态调整的方式自动改变标签估计式中的系数,使得标签估计个数随着已识别的标签数动态变化,从而估计下一帧待识别标签数;而对于帧长调整,根据估计的标签数,通过帧长与标签数分组的关系确定.通过MATLAB进行仿真,结果表明,该算法能明显提高系统的吞吐率和稳定性.     

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。     

一种时间高效的易于实现的多标签射频识别技术

多标签碰撞问题严重影响射频识别RFID系统的识别效率.在研究子帧观测机制的基础上,针对常规动态帧时隙Aloha多标签防碰撞算法存在的复杂度高、时间效率低等问题,提出了一种基于子帧的动态帧时隙Aloha算法,其在识别过程中采取设定的子帧观测,运用空闲与碰撞时隙数的关系估计剩余标签数,再依据预估的结果优化设置新的帧长,显著提升了大容量多标签RFID系统的识别效率.该算法的运算复杂度低、计算量小,易于在常规RFID读写器中实现,工程应用前景广阔.仿真结果表明：同传统的Aloha类防碰撞算法相比,提出的算法具有复杂度低、稳定好、识别效率高等优势.     

一种RFID标签数字电路的ASIC设计与实现

结合UHF频段EPCGlobal Class0协议,设计出一种符合协议要求的被动式射频身份识别（RFID）标签的数字电路。对电路的框架设计和模块具体实现方法进行了详细阐述,基于Chartered 0．35um工艺标准单元库用Synopsys相关工具对该电路进行了前端综合和后端物理实现,并对电路的主要性能进行了简要的分析。仿真及测试结果表明该标签数字电路功能符合协议要求,与该协议下阅读器兼容。     

利用单片机的捕获功能自动识别铁路RFID标签数据

铁路标签分为机车标签和货车标签。2种标签被阅读器发射的射频能量激活后,将连续不断、周而复始返回标签中的数据帧发送给阅读器。阅读器将标签信号解调后送给单片机,单片机采用边沿捕获功能完成解码。机车标签帧头和货车标签帧头,以及它们的数据波形均是不相同的,正是利用它们各自信号的特征,可以自适应地识别出是机车标签还是货车标签,这样无论机车处于列车的什么位置,均不会出现误识别或漏识别现象。     

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。     

基于模运算标签分类的RFID标签防碰撞识别方法

为了解决射频识别(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,提出一种基于模运算标签分类的RFID标签防碰撞识别方法。引入一种检测信息碰撞的时隙选择信息,对标签所选取时隙的碰撞情况进行分析并估计标签数量;然后对标签EPC编码进行逐级的取模运算,将同余的标签归为一组。各个标签经过K次取模运算后,分为2k组,每组只有发生少量碰撞位的标签。再将标签按照分组对应的时隙发送,碰撞标签采用二叉树后退式算法处理。本方法极大的提高了标签的识别效率,适用于射频识别系统中阅读器对于大量电子标签的快速识别。     

A New Scalable Lightweight Grouping Proof Protocol for RFID systems

Radio-frequency Identification (RFID) grouping proof protocol is widely used in medical healthcare industry, transportation industry, crime forensics and so on,it is a research focus in the field of information security. The RFID grouping proof protocol is to prove that some tags belong to the same group and exist simultaneously. To improve the applicability of the RFID grouping proof protocol in low cost tag applications, this paper proposes a new scalable lightweight RFID grouping proof protocol. Tags in the proposed protocol only generate pseudorandom numbers and execute exclusive-or(XOR) operations. An anti-collision algorithm based on adaptive 4-ary pruning query tree (A4PQT) is used to identify the response message of tags. Updates to secret information in tags are kept synchronized with the verifier during the entire grouping proof process. Based on these innovations, the proposed protocol resolves the scalability issue for low-cost tag systems and improves the efficiency and security of the authentication that is generated by the grouping proof. Compared with other state-of-the art protocols, it is shows that the proposed protocol requires lower tag-side computational complexity, thereby achieving an effective balance between protocol security and efficiency.     

可证明安全的RFID标签所有权转移协议

随着物品所有权的转移,其上附着的RFID标签的所有权也需要转移。安全和隐私问题是标签所有权转移过程中需要研究的重点问题。在通用可组合框架下,形式化定义了RFID标签所有权转移的理想函数。提出了一个新的轻量级RFID标签所有权转移协议,并证明了该协议安全地实现了所定义的理想函数,即具有双向认证、标签匿名性、抗异步攻击、后向隐私保护和前向隐私保护等安全属性。与已有的RFID标签所有权转移协议相比,新协议中RFID标签的计算复杂度和存储空间需求都较低,并且与新旧所有者的交互较少,能够更加高效地实现低成本标签的所有权转移。     

Instant collision resolution for tag identification in RFID networks

In this paper, we approach the problem of identifying a set of objects in an RFID network. We propose a modified version of Slotted Aloha protocol to reduce the number of transmission collisions. All tags select a slot to transmit their ID by generating a random number. If there is a collision in a slot, the reader broadcasts the next identification request only to tags which collided in that slot. Besides, we present an extensive comparative evaluation of collision resolution protocols for tag identification problem in RFID networks. After a quick survey of the best performing RFID tag identification protocols, both deterministic and probabilistic, we present the outcome of intensive simulation experiments set up to evaluate several metrics, such as the total delay of identification process and the bit complexity of reader and tags. The last metric is strictly related to energy constraints required by an RFID system. The experiments point out that our protocol outperform all the other protocols in most cases, and matches them in the others.     

Adaptive Binary Splitting: A RFID Tag Collision Arbitration Protocol for Tag Identification

In the RFID system, a reader recognizes tags through communications over a shared wireless channel. When multiple tags transmit their IDs at the same time, the tag-to-reader signals lead to collision. Tag collision arbitration for passive RFID tags is significant for fast identification since collisions disturb the reader's identification process. This paper presents an Adaptive Binary Splitting (ABS) protocol which is an improvement on the binary tree protocol. To reduce collisions and identify tags efficiently, ABS uses information which is obtained from the last processes of tag identification. Our performance evaluation shows that ABS outperforms other tree based tag anti-collision protocols. This work was supported by Korea Research Foundation Grant (KRF-2005-041-D00680).     

无后台服务器的射频识别标签安全查询协议

在许多射频识别(RFID)应用中,经常需要在多个标签中确定某个特定标签是否存在。在这种环境下,标签查询协议必不可少。然而,已有的协议要么存在安全漏洞,要么查询效率低下。利用Hash函数和时间戳,提出一个无后台服务器的RFID标签查询协议。GNY逻辑被用于证明新协议的正确性。分析显示提出的协议可以高效的实现特定标签的查询,且能够抵抗一些主要攻击,实现对标签隐私的保护。     

Enhancing Privacy and Security of RFID System with Serverless Authentication and Search Protocols in Pervasive Environments

One of the recent realms that gathered attention of researchers is the security issues of Radio Frequency Identification (RFID) systems that have tradeoff between controlled costs and improved efficiency. Evolvement and benefits of RFID technology signifies that it can be low-cost, efficient and secured solution to many pervasive applications. But RFID technology will not intermingle into human lives until prevailing and flexible privacy mechanisms are conceived. However, ensuring strong privacy has been an enormous challenge due to extremely inadequate computational storage of typical RFID tags. So in order to relieve tags from responsibility, privacy protection and security assurance was guaranteed by central server. In this paper, we suggest serverless, forward secure and untraceable authentication protocol for RFID tags. This authentication protocol safeguards both tag and reader against almost all major attacks without the intervention of server. Though it is very critical to guarantee untraceability and scalability simultaneously, here we are proposing a scheme to make our protocol more scalable via ownership transfer. To the best of our knowledge this feature is incorporated in the serverless system for the first time in pervasive environments. One extension of RFID authentication is RFID tag searching, which has not been given much attention so far. But we firmly believe that in near future tag searching will be a significant issue RFID based pervasive systems. So in this paper we propose a serverless RFID tag searching protocol in pervasive environments. This protocol can search a particular tag efficiently without server’s intervention. Furthermore they are secured against major security threats.     

Evaluating the energy consumption of the RFID tag collision resolution protocols

RFID technology acts as a bridge to connect the physical world with the digital space, and RFID system is pervading our daily life in the last few years. The energy consumed by the reader and a tag in resolving the collisions caused by multiple tags is a key issue that affects life time of mobile reader and active tags, as well as the identification accuracy of passive tags. In this paper, the energy consumed by the reader and a tag in resolving the tag collision is examined for the commonly used RFID tag collision resolution protocols, including the frame slotted ALOHA based and the binary query tree based protocols. Numeric evaluation is also performed and the result verifies that regarding to energy consumption, the dynamic frame slotted ALOHA protocol for the Class-1 RFID system performs best among the frame slotted ALOHA protocols, and the modified binary query tree protocol also performs better than the standard binary query tree protocols.     

A Scheme to Increase Throughput in Framed‐ALOHA‐Based RFID Systems with Capture

In this paper, a scheme to increase the throughput of RFID systems is presented, which considers the capture effect in the context of framed ALOHA protocol. Under the capture model in which the probability of one tag is identified successfully depending on the number of tags involved in the collision, two probabilistic methods for estimating the unknown number of tags are proposed. The first method is the maximum likelihood estimation method, and the second method is an approximate algorithm for reducing the computational time. The optimal frame size condition to maximize the system throughput by considering the capture effect is also presented.