Bi-slotted tree based anti-collision protocols for fast tag identification in RFID systems

This paper is intended to present bi-slotted tree based RFID tag anti-collision protocols, bi-slotted query tree algorithm (BSQTA) and bi-slotted collision tracking tree algorithm (BSCTTA). Diminishing prefix overhead and iteration overhead is a significant issue to minimize the anti-collision cost. For fast tag identification, BSQTA and BSCTTA use time divided responses depending on whether the collided bit is `0' or `1' at each tag ID. According to the simulation results, BSQTA and BSCTTA require less time consumption for tag identification than the other tree based RFID tag anti-collision protocols     

Improved RFID anti-collision algorithm

In this paper, we propose an improved anti-collision technique based on the binary search algorithm. The improvement is achieved thanks to the manner of the requests’ building. This latter reduces considerably the responding tag's numbers and therefore, decreases the probability of bit's collision. Further, the algorithm provides a noticeable advantage for the length of transmitted binary data compared against basic binary search and dynamic binary search algorithms. Besides, it provides same performance in terms of average request's number making the identification process faster, and the expose time of information is then reduced.     

RFID reader collision problem: performance analysis and medium access

The RFID reader collision problem, in which an RFID reader's interrogation is interfered by other concurrent readers' transmission, is considered an important issue to reliable operation and thus to the wide‐spread deployment of RFID networks. In this paper, we present modeling and analysis of the RFID reader collision problem. We observe asymmetry between an RFID reader's and a tag's communication capabilities and develop an RFID radio model based on the asymmetry. By the model, we characterize the spatial reuse of RFID reader networks, and derive concurrent interrogation distance beyond which readers can transmit simultaneously without causing collision and the carrier sense threshold corresponding to the distance. We also examine the dual‐channel mode where available bandwidth is divided into two channels by which reader‐to‐tag communication and tag‐to‐reader communication are separated. We analyze and evaluate the performance of the dual‐channel mode in terms of spatial reuse and interrogation completion time. Copyright © 2010 John Wiley & Sons, Ltd.     

A new anti‐collision protocol based on information of collided tags in RFID systems

Radio frequency identification (RFID) technology has recently become an integral part of a wide range of applications. One of the challenges in RFID systems is the tag anti‐collision issue, for which several anti‐collision tag identification protocols have been proposed. This paper proposes a novel slotted ALOHA‐based RFID tag anti‐collision algorithm which can be employed for tag identification. The main idea of this algorithm is to use the information available in collision slots, called collided data, to identify tags uniquely. For this purpose, the collision slots that include only two tags are selected. Then, the non‐conflict bits in these slots are used to possibly identifying the tags. Because in the proposed algorithm readers use both single slots and also the collision slots for tag identification, the performance is increased significantly compared with other protocols. Results of the study indicate that in the proposed algorithm, the optimal frame size for an individual tag number is equal to the half of tags number and the efficiency of the proposed protocol is improved to about 73%. Copyright © 2015 John Wiley & Sons, Ltd.     

基于比特查询的多进制树标签防碰撞识别协议

多标签碰撞问题被认为是射频识别系统中的一个关键问题.近来,许多基于比特追踪技术的查询树算法被提出用于有效的解决标签碰撞问题,然而由于无用的碰撞比特信息和空闲时隙的存在,这些查询树算法的性能都有待进一步提升.本文提出了一种基于比特查询的查询方法,该算法使得标签返回一个映射过比特串来取代原始的ID序列.同传统的ID查询相比较,比特查询不仅可以消除空闲查询还可以将碰撞标签分成更多子集并充分利用碰撞比特信息.基于该比特查询方法,我们提出了一种基于比特查询的多进制树（Bit query based M-ary tree,BQBMT）新型查询树算法,它通过多进制树迭代的分离碰撞,并通过比特查询模式和ID查询模式之间的最佳切换来快速识别标签.理论分析和仿真结果显示,BQBMT算法的的系统效率接近0.89,超过了现有的QT算法和混合防碰撞算法.     

TOA estimation of UWB backscattering RFID tag with dual pulse modulation for clutter suppression

To realize precise localization for UWB backscattering RFID system, the arrival time of the direct path in the received signal (referred as time of arrival (TOA)) needs to be accurately estimated. The background clutter is one of the major factors that deteriorates the TOA estimation accuracy in backscattering RFID system. To suppress the background clutter while maintain low‐complexity system design, we propose a novel UWB backscattering RFID system with its tag being implemented with dual pulse (DP) modulation. By transforming the mathematical model of received signal into a proper form, we discover the tag's sequence selection criteria which are able to mitigate the background clutter. For the proposed tag coded with dedicated sequences, a two‐stage TOA estimation algorithm able to effectively mitigate clutter is developed. Simulation results show that the proposed RFID system coupled with the algorithm is able to achieve accurate TOA estimation in the environment where the clutter overwhelms the tag response. Copyright © 2010 John Wiley & Sons, Ltd.     

Gen2‐Based Tag Anti‐collision Algorithms Using Chebyshev's Inequality and Adjustable Frame Size

Arbitration of tag collision is a significant issue for fast tag identification in RFID systems. A good tag anti‐collision algorithm can reduce collisions and increase the efficiency of tag identification. EPCglobal Generation‐2 (Gen2) for passive RFID systems uses probabilistic slotted ALOHA with a Q algorithm, which is a kind of dynamic framed slotted ALOHA (DFSA), as the tag anti‐collision algorithm. In this paper, we analyze the performance of the Q algorithm used in Gen2, and analyze the methods for estimating the number of slots and tags for DFSA. To increase the efficiency of tag identification, we propose new tag anti‐collision algorithms, namely, Chebyshev's inequality, fixed adjustable framed Q, adaptive adjustable framed Q, and hybrid Q. The simulation results show that all the proposed algorithms outperform the conventional Q algorithm used in Gen2. Of all the proposed algorithms, AAFQ provides the best performance in terms of identification time and collision ratio and maximizes throughput and system efficiency. However, there is a tradeoff of complexity and performance between the CHI and AAFQ algorithms.     

一种快速获取同频数据的防碰撞算法

文章在碰撞二叉树算法(CT)技术的基础上提出一种用于433 MHz频段下的标签防碰撞算法——改进型碰撞二叉树算法(ICT),可以很好地对各类土地的地形分布数量等特征进行测量。该算法根据首次碰撞码字进行前缀生成和标签组区分,在标签快速识别中,对每一个标签使用了一个计数器和一个指针,用来记录阅读器的历史序列,从而使得阅读器不需要传输整个前缀序列。仿真结果表明,ICT算法在当标签ID具有类似的前缀时,表现出优于CT算法的性能。     

Multi-branch query tree protocol for solving RFID tag collision problem

The technology of anti-collision is a key point in radio frequency identification （RFID） system. To avoid data collision, there are two approaches： ALOHA based algorithm and binary tree （BT） based algorithm. However, these cannot solve the collision problem completely, especially when the tag quantity is big and the tag ID is long. In this article, we present a multi-branch query tree （MBQT） protocol based on balanced incomplete block design （BIBD） code, and use 16-bit vectors derived from the BIBD as query prefix symbols of RFID reader. Compared with the conventional anti-collision algorithm, the theoretic analysis and simulation show that the proposed protocol improves the identification efficiency.     

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 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.     

LRST：低冗余搜索树防碰撞算法

针对RFID标签防碰撞树型算法在识别过程中因询问命令过多、过长而产生大量冗余数据导致通信开销过大的问题,在后退式动态搜索树算法的基础上提出一种低冗余搜索树防碰撞算法（LRST）：为减少询问次数,提出了“一问两答”询问方式,即碰撞标签根据最高碰撞位比特分别在第一个时隙或第二个时隙响应;为减小询问命令的长度,用计数器替代标签中的前缀匹配电路,使算法不再需要前缀作为询问命令的标识参数;此外,提出的预测识别和标签屏蔽机制可节省不必要的询问。理论分析和仿真结果表明,通信开销大大降低。     

System synchronization and channel estimation analysis for IEEE 802.16e OFDMA downlink system

System synchronization and channel estimation are two key problems of IEEE 802.16e Orthogonal Frequency Division Multiplex Access (OFDMA) downlink system. According to the standard, system synchronization is completed through the cell search procedure, which includes two steps: frame detection and cell‐ID identification. First, based on the special time‐domain (TD) and frequency‐domain (FD) structures of the preamble, we propose two novel frame detection ms: the TD algorithm and the FD algorithm. Their robustness performance is nearly the same, and the complexity of the FD algorithm is only of that of the TD algorithm. Then, an efficient cell‐ID identification algorithm is proposed, in which the necessary correlation length can be dramatically shortened even without any a priori channel knowledge. Thereby, it greatly reduces the cell search time. As for the problem of channel estimation, a cluster‐based channel estimation method is proposed. It is based on the special pilot distribution of IEEE 802.16e and utilizes the continuity of channel variations to mitigate the impact of time‐variant channel. System simulation results show that the proposed algorithms are both robust and efficient. Copyright © 2008 John Wiley & Sons, Ltd.     

Design of an Ultra‐Compact UHF Passive RFID Tag Antenna for a Medical Sample Tube

In this letter, a small‐sized ultra‐high frequency (UHF) RFID tag antenna for a medical sample tube is proposed. The RFID tag antenna is designed and fabricated based on the circular loop antenna used in the UHF band (Korea standard, 917 MHz to 923.5 MHz). The tag antenna size is reduced using a circular meander stub. The antenna has a physical size of 8 mm, which is about λ/40 in electrical length. The proposed tag antenna is molded into a medical sample and multitag identification is performed.     

Novel RFID anti-collision algorithm based on the Monte–Carlo query tree search

Tag collision is a pressing issue in radio frequency identification systems which significantly lowers the system performance if not mitigated carefully. This paper presents the Monte–Carlo Query Tree Search (MCQTS) method as a novel and fast anti-collision algorithm. This method combines the capabilities of the conventional Monte–Carlo Tree Search and Query Tree by applying a few heuristics on the tree traversal to raise the chance of facing the most promising states. The collision mitigation based on the MCQTS is presented and its performance in terms of time, and space (memory) complexity is analytically verified. Simulations are performed, and the effects of tree size, number of tags, and tag ID length on the performance of the proposed method are investigated. The results are compared to the previously presented tree-based algorithms, and it is shown that for typical tag lengths, the MCQTS method performs between 3.89% and 62.06% (in average) faster than the conventional methods for multi-tag identification.

     

Novel tag estimation method by use of Manchester coding in RFID systems

Radio frequency identification suffers from tag collision issue. ALOHA‐based algorithms are useful and practical groups of tag anti‐collision algorithm among others. Some standards such as EPCglobal Class‐1 Generation‐2 use some kind of dynamic framed slotted ALOHA (DFSA) to cope with tag collision. DFSA efficiency depends on estimating the number of unidentified tags in each identification cycle accurately. So tag estimation is one of the challenging issues in DFSA. In this paper, we use Manchester coding to compute the lower bound of collided tags in a frame and then add α as an additional value to computed value according to the difference between optimal number of collision slots and calculated number of collision slots. Then, we evaluate and compare our method with other proposed methods.     

SVM‐Based Speaker Verification System for Match‐on‐Card and Its Hardware Implementation

Using biometrics to verify a person's identity has several advantages over the present practice of personal identification numbers (PINs) and passwords. To gain maximum security in a verification system using biometrics, the computation of the verification as well as the storing of the biometric pattern has to take place in a smart card. However, there is an open issue of integrating biometrics into a smart card because of its limited resources (processing power and memory space). In this paper, we propose a speaker verification algorithm using a support vector machine (SVM) with a very few features, and implemented it on a 32‐bit smart card. The proposed algorithm can reduce the required memory space by a factor of more than 100 and can be executed in real‐time. Also, we propose a hardware design for the algorithm on a field‐programmable gate array (FPGA)‐based platform. Based on the experimental results, our SVM solution can provide superior performance over typical speaker verification solutions. Furthermore, our FPGA‐based solution can achieve a speed‐up of 50 times over a software‐based solution.     

Scale and Rotation Invariant Optical ID Tags for Automatic Vehicle Identification and Authentication

We present a scale and/or rotation invariant ID tag to achieve real time automatic vehicle identification for inventory or security purposes. We focus our attention to achieve invariance with respect to scale variations and in-plane rotations of the ID tag. Both distortions must be taken into account in the design of a vehicle identification system operating from above the area of interest (e.g., aerial detection and authentication). In our proposal, distortion invariance is achieved by both multiplexing the ID tag a priori information, and developing an appropriate topology for encoding the information on the ID tag. To increase security, the designed ID tag consists of an optical code containing an encrypted signature which identifies the vehicle. The applied encryption procedure follows the double phase encoding technique, which provides robustness to different degradation sources such as noise, occlusion, scratches, etc. that may affect the ID tag. Once the ID tag is captured by the processor, decryption of the hidden signature is carried out, and its correlation with a previously stored reference signal allows either the identification or the rejection of the authorized vehicle. Numerical results are provided to show the feasibility of the system. The proposed system may have broad applications in transportation, homeland security, and remote vehicle inventory control.     

BER‐modified regenerative protocols for OFDM‐based two‐way wireless relay channel

It is well known that symbol‐level regenerative relay protocols suffer the error propagation problem because receiver decodes blindly and overlooks the probability of relay forwarding wrong bits. In a two‐way relay networks, the problem still exists in both network coding (decode‐and‐forward) and physical network coding (denoise‐and‐forward) protocols. For today's widely adopted wide band Orthogonal frequency‐division multiplexing (OFDM) systems, error propagation will dramatically restrict the system's end‐to‐end performance especially when frequency selective fading exists. In this paper, we propose a bit error rate (BER) modified decoding algorithm for these OFDM‐based two‐way symbol‐level regenerative relay strategies. By confining the confidence level of demodulated soft information according to the likelihood of relay having made an error on each bit, this proposed algorithm significantly boosts the end‐to‐end BER performance of the system. Copyright © 2015 John Wiley & Sons, Ltd.     

智能滑套内低频段RFID 标签识别率的研究

实际应用中智能滑套内低频段RFID 标签存在识别率低的问题,从射频识别技术的工作机理出发,借助MATLAB 仿真软件,对低频螺线管天线感应电压特性进行了仿真分析,讨论了读写器天线长度和内径对识别率的影响,提出了基于井下智能滑套的RFID 通信系统最佳天线部署。同时为减弱井下复杂工况环境对标签识别率的影响,设计了读写器天线自适应阻抗匹配系统,建立一套基于井下RFID 通信系统识别率的模拟试验平台,验证仿真设计结果的正确性。