基于二进制树的RFID系统自适应多分支防碰撞算法

为提高射频识别(RFID)系统的识别效率,研究了系统的标签防碰撞问题。考虑到对标签进行多分支处理能够有效地提高RFID系统标签识别效率,而传统的多分支防碰撞算法都是在标签估计的基础上对标签进行最优分组,标签估计产生的时延和误差都会影响整体的识别效率,提出了一种基于二进制树的自适应多分支(AMB)防碰撞算法。该算法根据二进制树结构特点,利用识别的标签数目对树结构中右节点标签进行估计并进行分组识别,经过多次调整的自适应多分支防碰撞算法,可以规避一次标签估计所引入的估计误差,从而提高系统的识别效率。仿真结果表明自适应多分支算法可以大大提高标签识别效率,在标签数量较大时系统效率可达43%左右。同时该算法实现简单,只需在阅读器中增加若干计数器,不需要改变任何空中接口,很容易与现有协议兼容。     

智能包装中的RFID标签防碰撞算法研究

目的 解决目前物流系统中智能包装RFID标签冲突的问题。方法 在研究已有防碰撞算法的性能和缺点基础上,针对大量标签场景设计一种分组动态帧时隙的混合查询树（GDFSA-HQT）算法。该算法在每一轮识别之后估计还没有识别的标签数量,如果还没有识别的标签数量小于或等于354个,则先采用动态帧时隙ALOHA（DFSA）算法对标签进行识别,再采用混合树查询算法（HQT）进行标签识别;若未被识别标签数大于354个,则先对标签进行分组处理,再分别采用DFSA和HQT进行标签识别。结果 仿真实验表明,GDFSA-HQT算法的吞吐率能够保持在0.82左右。结论 GDFSA-HQT算法解决了标签碰撞问题,在大量智能包装的物流系统中具有良好的应用前景。     

A Frame Breaking Based Hybrid Algorithm for UHF RFID Anti-Collision

Multi-tag collision imposes a vital detrimental effect on reading performance of an RFID system. In order to ameliorate such collision problem and to improve the reading performance, this paper proposes an efficient tag identification algorithm termed as the Enhanced Adaptive Tree Slotted Aloha (EATSA). The key novelty of EATSA is to identify the tags using grouping strategy. Specifically, the whole tag set is divided into groups by a frame of size F. In cases multiple tags fall into a group, the tags of the group are recognized by the improved binary splitting (IBS) method whereas the rest tags are waiting in the pipeline. In addition, an early observation mechanism is introduced to update the frame size to an optimum value fitting the number of tags. Theoretical analysis and simulation results show that the system throughput of our proposed algorithm can reach as much as 0.46, outperforming the prior Aloha-based protocols.     

A Dynamic Multi-ary Query Tree Protocol for Passive RFID Anti-collision

In this paper, a dynamic multi-ary query tree (DMQT) anti-collision protocol for Radio Frequency Identification (RFID) systems is proposed for large scale passive RFID tag identification. The proposed DMQT protocol is based on an iterative process between the reader and tags which identifies the position of collision bits through map commands and dynamically encodes them to optimize slots allocation through query commands. In this way, the DMQT completely eliminates empty slots and greatly reduces collision slots, which in turn reduces the identification time and energy costs. In addition and differently to other known protocols, the DMQT does not need to estimate the number of tags, reducing the protocol implementation complexity and eliminating the uncertainty caused by the estimation algorithm. A numerical analysis shows that DMQT has better performance than other algorithms for a number of tags larger than 300. Meanwhile, when the number of tags is 2000 and the tag identity (ID) length is 128 bits, the total identification time is 2.58 s and the average energy cost for a tag identification is 1.2 mJ, which are 16.9% and 10.4% less than those of state-of-the-art algorithms, respectively. In addition, a DMQT extension based on ACK command has also been presented to deal with capture effect and avoid missing identification.

     

基于二元指数后退的电子标签防碰撞算法

为解决目前现有电子标签防碰撞算法在电子标签数量较大时,读取效率低且耗时较长的问题,提出了一种基于二元指数后退的时隙选择算法,当碰撞发生时,改进算法以二进制指数方式进行时隙的增加,并随机选择时隙发送数据,重复这个过程直到所有标签被正确读出。仿真试验表明,在电子标签数量急剧增加时,改进算法的读取效率较高,电子标签读取所需时隙基本不增加。     

判断二进制树中标签识别完毕的方法

分析了射频识别(RFID)系统阅读器与标签通信的二进制树算法,指出在标签识别过程中,阅读器并不知道是否识别完标签,阅读器会以连续多次没有接收标签响应为依据结束对标签的查询,这样往往会造成标签漏读或浪费时间在已识别完的标签上。基于此分析,提出了判断二进制树中标签识别完毕的方法。该方法通过在阅读器中设置计数器,就可以很好地跟踪标签的识别情况,准确地判断出标签是否识别完毕。分析结果表明,该方法可以准确地判断标签是否识别完毕,增加系统识别效率和可靠性。     

RFID包装系统中防冲突算法研究

目的解决现阶段包装箱管理过程中RFID标签冲突的问题。方法在分析已有的解决标签冲突算法的基础上,采用多线程技术、后退式二进制防冲突算法和优化的数据结构等方法,设计并实现一种新的防冲突算法。RFID读写器发送一个三元组命令,RFID标签应答冲突位的信息,减少数据传输量;采用堆栈存储RFID读写器发送的命令,减少识别冲突的次数;利用多线程处理思想,对标签进行分类处理,缩短冲突处理的时间。结果经过仿真分析,这种并发执行的后退式二进制RFID防冲突算法效率可提高约51%。结论该算法解决了RFID标签冲突,提高了多标签情况下的读写效率,很好地解决了包装箱管理系统中RFID标签的功能和性能的问题。     

A Novel Time-aware Frame Adjustment Strategy for RFID Anti-collision

Recently, object identification with radio frequency identification (RFID) technology is becoming increasingly popular. Identification time is a key performance metric to evaluate the RFID system. The present paper analyzes the deficiencies of the state-of-the-arts algorithms and proposes a novel sub-frame-based algorithm with adaptive frame breaking policy to lower the tag identification time for EPC global C1 Gen2 UHF RFID standard. Through the observation of slot statistics in a sub-frame, the reader estimates the tag quantity and efficiently calculates an optimal frame size to fit the unread tags. Only when the expected average identification time in the calculated frame size is less than that in the previous frame size, the reader starts the new frame. Moreover, the estimation of the proposed algorithm is implemented by the look-up tables, which allows dramatically reduction in the computational complexity. Simulation results show noticeable throughput and time efficiency improvements of the proposed solution over the existing approaches.     

"互联网+计量"模式下样品动态追踪 管理系统研究

针对传统人工和半自动化条形码的管理系统对工作的实时性和便捷性存在的缺陷与弊端，设计了一种基于RFID技术的样品动态追踪管理系统，实现了通过访问应用系统准确定位、动态跟踪送检样品、自动更新信息和无线升级电子标签应用程序的功能。系统由路标激励器、半有源电子标签、阅读器和应用系统组成。电子标签采用低功耗设计，经测试，整机休眠电流低至6启动防碰撞算法，200个激励器同时被激励器时，平均漏读率为0.5%，误判率为0%。     

基于调度方式的阅读器防碰撞算法

目的阅读器碰撞是射频识别技术(RFID)的常见问题,常见的防碰撞算法没有同时考虑阅读器碰撞的2种情况,并且对硬件要求高,这影响了RFID系统数据通信的效率。提出了基于调度的阅读器防碰撞算法。方法采用中央服务器调度方式,建立混合整数规划模型,按一定的规则,将频率和时隙分配给阅读器;在2种不同阅读器距离及同时考虑吞吐率和均衡率的情况下,对提出的算法与CSMA算法进行了对比。结果在同时考虑吞吐率和均衡率的条件下,基于调度的阅读器防碰撞算法优于CSMA算法。结论该算法能够提高吞吐率和均衡率。     

基于改进ALOHA算法的RFID标签防碰撞研究

目的 为提高射频识别技术(Radio Frequency Identification,RFID)标签识别成功率,以及包装生产线自动分拣效率、智能化水平.方法 以包装生产线检测系统为研究对象,结合RFID技术设计一种自动包装、检测、配送系统.介绍RFID检测系统,主要包括标签、阅读器、天线和控制系统.针对RFID识别过程中标签碰撞问题,提出一种改进ALOHA算法,采用动态预测权值估计标签数目使标签数目与数据帧长度大致相等.通过实验验证ALOHA算法的有效性.结果 实验结果表明,碰撞比率平均值只有1.1％,整个系统的检测成功率可以达到99.6％;所述改进ALOHA算法可以有效避免标签碰撞.结论 该系统能够自动完成检验,并且用时较少,检验过程中正确率较高,具有较高的市场应用价值.     

A Physical Layer Algorithm for Estimation of Number of Tags in UHF RFID Anti-Collision Design

A priori knowledge of the number of tags is crucial for anti-collision protocols in slotted UHF RFID systems. The number of tags is used to decide optimal frame length in dynamic frame slotted ALOHA (DFSA) and to adjust access probability in random access protocols. Conventional researches estimate the number of tags in MAC layer based on statistics of empty slots, collided slots and successful slots. Usually, a collision detection algorithm is employed to determine types of time slots. Only three types are distinguished because of lack of ability to detect the number of tags in single time slot. In this paper, a physical layer algorithm is proposed to detect the number of tags in a collided slot. Mean shift algorithm is utilized, and some properties of backscatter signals are investigated. Simulation results verify the effectiveness of the proposed solution in terms of low estimation error with a high SNR range, outperforming the existing MAC layer approaches.     

Tag identification enhancement by using a distributed antenna structure for radio frequency identification systems

This study presents a distributed antenna structure operating at a frequency of 915 MHz to increase the tag identification sensitivity for passive radio frequency identification (RFID) systems. The distributed antennas are connected to a reader with a four-port power splitter/combiner which consists of Wilkinson power splitters (WPSs), band pass filters (BPFs) and power amplifiers (PAs). Due to the polarisation of the electromagnetic field, the antennas are positioned on opposite sides in both vertical and horizontal directions of the object. This positioning improves the performance of the system, and increases the sensitivity when identifying unclearly positioned tags. An experimental RFID system is also set up to demonstrate the proposed structure. Simulation and experimental results indicate that using four distributed patch antennae can improve tag identification in passive RFID systems.     

A Cross Layer Protocol for Fast Identification of Blocked Tags in Large-Scale RFID Systems

Blocker tag attack is one of the denial-of-service (DoS) attacks that threatens the privacy and security of RFID systems. The attacker interferes with the blocked tag by simulating a fake tag with the same ID, thus causing a collision of message replies. In many practical scenarios, the number of blocked tags may vary, or even be small. For example, the attacker may only block the important customers or high-value items. To avoid the disclosure of privacy and economic losses, it is of great importance to fast pinpoint these blocked ones. However, existing works do not take into account the impact of the number of blocked tags on the execution time and suffer from incomplete identification of blocked tags, long identification time or privacy leakage. To overcome these limits, we propose a cross layer blocked tag identification protocol (CLBI). CLBI consists of multiple rounds, in which it enables multiple unblocked tags to select one time slot and concurrently verify them by using tag estimation in physical layer. Benefiting from the utilization of most collision slots, the execution time can be greatly reduced. Furthermore, for efficient identification of blocked tags under different proportions, we propose a hybrid protocol named adaptive cross layer blocked tag identification protocol (A-CLBI), which estimates the remaining blocked tag in each round and adjusts the identification strategy accordingly. Extensive simulations show that our protocol outperforms state-of-the-art blocked tags identification protocol.     

A statistical method for assessing peptide identification confidence in accurate mass and time tag proteomics

Current algorithms for quantifying peptide identification confidence in the accurate mass and time (AMT) tag approach assume that the AMT tags themselves have been correctly identified. However, there is uncertainty in the identification of AMT tags, because this is based on matching LC-MS/MS fragmentation spectra to peptide sequences. In this paper, we incorporate confidence measures for the AMT tag identifications into the calculation of probabilities for correct matches to an AMT tag database, resulting in a more accurate overall measure of identification confidence for the AMT tag approach. The method is referenced as Statistical Tools for AMT Tag Confidence (STAC). STAC additionally provides a uniqueness probability (UP) to help distinguish between multiple matches to an AMT tag and a method to calculate an overall false discovery rate (FDR). STAC is freely available for download, as both a command line and a Windows graphical application.     

Informative SNP selection methods based on SNP prediction

The search for the association between complex diseases and single nucleotide polymorphisms (SNPs) or haplotypes has recently received great attention. For these studies, it is essential to use a small subset of informative SNPs, i.e., tag SNPs, accurately representing the rest of the SNPs. Tag SNP selection can achieve: 1) considerable budget savings by genotyping only a limited number of SNPs and computationally inferring all other SNPs or 2) necessary reduction of the huge SNP sets (obtained, e.g., from Affymetrix) for further fine haplotype analysis. In this paper, we show that the tag SNP selection strongly depends on how the chosen tags will be used-advantage of one tag set over another can only be considered with respect to a certain prediction method. We show how to separate tag selection from SNP prediction and propose greedy and local-minimization algorithms for tag SNP selection. We give two novel approaches to SNP prediction based on multiple linear regression (MLR) and support vector machines (SVMs). An extensive experimental study on various datasets including ten regions from hapMap project shows that the MLR prediction combined with stepwise tag selection uses fewer tags than the state-of-the-art method of Halperin The MLR-based method also uses on average 30% fewer tags than IdSelect for statistical covering all SNPs. The tag selection based on SVM SNP prediction uses fewer tags to achieve the same prediction accuracy as the methods of Halldorsson     

Feasibility of ultra-wideband SAW RFID tags meeting FCC rules

We discuss the feasibility of surface acoustic wave (SAW) radio-frequency identification (RFID) tags that rely on ultra-wideband (UWB) technology. We propose a design of a UWB SAW tag, carry out numerical experiments on the device performance, and study signal processing in the system. We also present experimental results for the proposed device and estimate the potentially achievable reading distance. UWB SAW tags will have an extremely small chip size (<0.5 times 1 mm²) and a low cost. They also can provide a large number of different codes. The estimated read range for UWB SAW tags is about 2 m with a reader radiating as low as <0.1 mW power levels with an extremely low duty factor.     

硅酸镓镧单晶材料的声表面波标签研究

声表面波射频识别标签在射频标签领域获得广泛关注,其中对标签基底材料的研究也成了研究热点。文章旨在研究使用硅酸镓镧单晶材料为压电基底的声表面波标签的标签特性。对使用硅酸镓镧单晶材料为压电基底的声表面波标签进行频域和时域分析,并结合有限元分析方法,对标签的特征频率、叉指换能器(Interdigital Transducer, IDT)的反射系数、叉指电极金属化比、金属电极厚度以及标签回波特性进行研究分析,提取了耦合模COM(Coupled-mode)模型参数。分析结果表明了压电效应是声表面波的谐振与反谐振频率存在的根源,验证了脉冲幅度编码方式,并为使用硅酸镓镧材料作为压电基底的声表面波标签的制作提供了仿真实验依据。     

Identification of SAW ID-tags using an FSCW interrogation unit and model-based evaluation

Surface acoustic wave (SAW) devices are well suited for the application as wireless and completely passive identification (ID)-tag. They operate even under harsh environmental conditions, especially under high temperatures. Interrogation units operate similar to conventional radar systems and therefore, have the same resolution restrictions when an inverse fast Fourier transformation (IFFT) is applied. The application of model-based algorithms to the evaluation of identification tags is presented and enhancements in either improved resolution or reduced system bandwidth are shown. Furthermore, optimizations in the coding scheme for reduced tag sizes are discussed, and measured results obtained by a built interrogation unit and fabricated ID-tags for an identification system are shown.     

Cross-layer design for tree-type routing and level-based centralised scheduling in IEEE 802.16 based wireless mesh networks

Infrastructure wireless mesh network, also named as mesh router, is one key topology for the next generation wireless networking. In this work, the performance optimisation for the infrastructure wireless mesh network is presented and the sub-optimum solution mechanism is investigated. A cross-layer design for tree-type routing, level-based centralised scheduling and distributed power control theme is proposed as the sub-optimum solution strategy. The cross-layer design relies on the channel information and the distributed transmission power control in the physical layer, and the wireless scheduling in the medium access control (MAC) layer, as well as the routing selection mechanism in the MAC upper layer. In this work, a modified distributed power control algorithm is proposed first. In addition, a tree-type routing construction algorithm for centralised scheduling is presented to improve the network throughput by jointly considering interference and hop-count to construct the routing tree. Simulation results show that the proposed cross-layer design strategy can effectively improve the network throughput performance, decrease the power consumption and achieve better performances.