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关键词： Radio frequency identification (RFID)   anti-collision algorithm   query tree   lock position   prediction instruction  

摘要： In the radio frequency identification technology system, there are too many time slots which are caused by tag collision, and the communication complexity is high. On the basis of the anti-collision algorithm of the binary tree and the quadtree query tree, the methods of locking the collision bit and predicting the child node are used, a newlock-bit hybrid querytree (novel lock-bit hybrid query tree, NLHQT) algorithm is proposed. In the algorithm, the collision bit information is extracted through the lock instruction, and the extracted collision bit information is predicted. While reducing the collision time slot, the reader generates a new query prefix through prediction, thereby avoiding the generation of idle child nodes. Compared with the improved hybrid query tree (IHQT) anti-collision algorithm and the regression lock adaptive multi-tree search (RLAMS), the algorithm in this paper is more effective in reducing the total number of time slots and communication complexity, and the efficiency of identifying tags can be effectively improved.

关键词： Implantable antennas   radio frequency identification (RFID)   wireless monitoring   cyber-prosthesis   battery-less  

摘要： Body core temperature is one of the most reliable biometric indicators for monitoring the health status of a person. The gold standard in clinical settings is a highly invasive procedure involving the insertion of a catheter into the pulmonary artery, which receives blood directly from the core of the body. However, if a patient needs to host an Implanted Medical Device (IMD), a precise body core temperature measurement can be obtained without causing them additional discomfort, by adding communication and sensing capability to the IMD itself. This paper proposes a possible augmentation of a passive metal-free aortic valve prosthesis with a wrapped C-dipole provided by an RFID-based temperature sensor for batteryless and wireless temperature monitoring from the inside. A robust transcardiac link can be achieved with at least 24 dBm interrogation power by using a small on-skin reader antenna, which is also robust against moderate mutual misalignment among the two devices. The temperature sensing capability of a true sensorized valve, evaluated by means of a heated liquid phantom, demonstrated the possibility of sensing typical physiological temperature gradients with an average accuracy of less than 0.25? w.r.t. a reference thermocouple.

关键词： Resonant ring   metal mountable   Internet of Things (IoT) systems   radio frequency identification (RFID)   bendable UHF tag antenna  

摘要： A new flexible substrate UHF RFID tag on metal with a resonant ring and surface-etched slots that can be read at a long distance is proposed in this paper. The tag has a compact footprint of 50 mm x 50 mm x 1.1 mm (0.152 lambda x 0.152 lambda x 0.003 lambda at 915 MHz). It consists of two rectangular patches with a closed resonant ring and 4 surface etching slots, a narrow inductive stub, and a square ground. With the above structure which can make the tag adjusts both the resistance and reactance of the chip. The antenna has 7 adjustable parameters and can also be resonated at different frequencies. In the simulation, the proposed tag reaches a high power transmission coefficient(99.99%), which is an almost perfect conjugate matching, and the tag can reach a long reading distance of about 11 m on the metal containers. Finally, the tag is fabricated on the flexible polyethylene terephthalate substrates and tested. With an EIRP(effective isotropic radiated power) of 4 W, the tag can be read at a long range of 7.29 meters on metal planes and 3.71 meters on curved metal surfaces.

关键词： 含水率   活立木   射频识别   极限学习机  

摘要： 近年来,森林资源的利用和保护变得越来越重要,如何有效管理森林资源是全世界共同研究的课题。其中,活立木含水率测量在活立树木的监测和管理中起到至关重要的作用,其测量精度对林业信息化产业的发展具有重要意义。目前有很多技术手段被运用在木材含水率的检测中,但是检测过程及结果中存在的高能耗、低适用性、低预测精度等问题还需要进一步解决。本课题针对活立木水分生理研究和林业信息化技术的发展需求,以活立木含水率的无损检测和高效识别为目标,开展了基于无源超高频射频识别技术（UHF RFID）的活立木含水率研究。论文的主要思路为:基于低功耗的射频识别技术获取射频信号数据,同时采集测量环境中关键环境参数的数据;接着改进和集成先进的机器学习技术,建立最佳的活立木含水率预测模型,实现对各类木材的含水率无损检测;最后通过大量实验验证了该在线预测模型,结果证明所提出的方案具有准确、无损、实用、低功耗的优点,满足目前林业物联网领域的含水率检测需求。论文的具体研究内容如下:（1）总结了国内外相关研究现状和无源超高频射频识别技术的特点,基于UHF RFID技术设计了一种超低成本的活立木含水率检测方案。在校园林站中建立了一个高效的数据采集系统,设计了上位机程序进行长期的数据采集操作,获取了反向散射信号中的接收信号强度指数（RSSI）和相位等信息并采集了其它关键环境参数数据,对数据进行预处理并基于改进支持度函数的数据加权融合策略对多标签数据进行了同构数据融合,验证了由RSSI和相位反演活立木含水率的可行性。（2）基于UHF RFID传感器,优化现有识别机制,提出了一种改进的在线序列并行极限学习机算法（OS-PELM）。OS-PELM对传统在线序列极限学习机（OS-ELM）中的隐藏层网络结构进行优化,通过探路者算法进行初始参数优化并使用在线神经元调整的策略调节模型参数,根据改进算法建立了预测模型并用于含水率预测系统。（3）基于实验室和室外活立木中采集到的大量数据,使用基于OS-PELM算法的含水率预测模型进行了活立木实测分析,实验结果表明OS-PELM算法的性能与传统的OS-ELM算法相比有显著提升,在四种不同种类的树木上（水杉、杨树、松树、山毛榉）都具有更高的准确率。通过鲁棒性实验证明了所提出的活立木含水率无损检测系统具有准确率高、稳定性好、鲁棒性强等优点,可以为目前林业物联网行业提供切实可行的方案。对于所有采集样本,所提出模型的预测值与实际值之间的MAE为0.224,RMSE为0.252,R2系数为0.9629。将基于OS-PELM算法的预测模型与其它四种算法（DE-OSELM、WE-OSELM、GSA-PELM、OLSPELM）进行比较,采取的优化策略在预测准确率上具有显著优势。综上所述,论文为实时、准确地预测活立木含水率提供了强有力的设计思路和技术支持,在国家林草局精准林业的示范推广中具有极为广阔的应用前景。

关键词： 石墨烯   纳米银线   透明天线   RFID   小尺寸   吉赫兹  

摘要： 随着无线通信技术的不断发展,军事、航空航天、车载无线通信等领域对天线提出了小型化与美观性的新要求。透明天线作为一种集合光学与射频技术的两大优势特点的新型天线,成为当下热门研究课题之一。然而,目前已报道的透明天线存在制备工艺复杂、材料易碎、导电性差和透光度低等问题。针对以上问题,本研究旨在设计并制备高性能透明天线,主要研究内容与创新点总结如下: 1、采用石墨烯和纳米银线材料制备复合导电薄膜,进行材料表征及光电性能测试。通过探究工艺参数对薄膜透光度及导电性能的影响,获得了薄膜最佳光电性能的制备条件。实验结果表明,石墨烯和纳米银线制备的复合导电薄膜,弥补了纳米银线薄膜的缺陷,并极大地提高了石墨烯薄膜的导电性能。最终制备的石墨烯/纳米银线复合薄膜透光率为86%,方阻值为7.8Ω/(15),满足预期设计要求。 2、针对现存的照明市场能源浪费以及农业粗放式管理的现象,本研究设计了一款谐振频率为915 MHz的透明超高频RFID标签天线,其结构为折叠偶极子。在谐振点的实测反射系数为-7.91 d B,辐射方向图与仿真结果高度吻合,标签最大识别距离为4.15 m。实测透明标签对于植物生长灯的光强性能基本无影响,透明RFID标签RSSI(Received Signal Strength Indicator)与温度呈线性关系。以上测试结果表明透明RFID标签在智慧农业的信息管理系统中具有巨大的应用潜力。 3、针对一些空间尺寸限制严格以及光学透光度要求高的应用场景,本研究设计了一款谐振频率为8.8 GHz的半波偶极子天线,辐射单元体的半波臂尺寸为4 mm×2 mm。实测谐振点的反射系数为-14.6 d B,E面辐射方向图呈倒“8”形状,H面辐射方向图呈全向性,辐射最大方向增益值为0.19 d Bi。对比现有的小尺寸透明石墨烯天线研究,本研究中的透明吉赫兹半波偶极子天线具有高增益、高辐射效率和小尺寸的优势。

关键词： Gain   microstrip antennas   patch antennas   slot antennas   RFID   UHF antennas  

摘要： This paper aims to enhance the gain of a microstrip patch antenna for ultra-high frequency (UHF) radio frequency identification (RFID) reader. The paper proposes a new antenna design that consists of a perfectconductor rectangular patch with a quasi H-shaped slot using a flame retardant substrate and an aluminum ground plane. In order to improve the gain while keeping a modest antenna size, an empirical parametric study is performed using the CST Studio Suite software. As a result, an enhanced slotted antenna design is obtained with a total size of 136 x 124 x 3 mm(3) and a gain of 5.24 dBi at 922-MHz frequency. Such a gain magnitude is shown to be significantly higher than those obtained by analogous single patch antennas.

关键词： Radiofrequency identification   Waveguide components   Dielectrics   Sensors   Monitoring   Media   Corrosion   Attenuation constant   dielectric particulate media   dielectric waveguide   RFID   wireless sensors  

摘要： Radio frequency identification (RFID) is a wireless communication technique that has a wide variety of applications in many fields. In some cases, the read range of the RFID transponder is a limiting factor to the application;thus, it is desired that the read range of a given RFID system be maximized. This paper presents a method to extend the read range of UHF RFID signal (860-960 MHz) by using cost-effective dielectric particulate materials (e.g., dry sand) as filler in dielectric waveguides, which is useful for applications that employ UHF RFID as a sensing or communication tool that need long read ranges, e.g., underground pipeline corrosion monitoring or leak detection. Reading tests conducted in both laboratory (air) and underground showed that the transmission of the UHF RFID signal through dielectric particulate media can considerably extend the read range of passive RFID transponders, which makes it a good material choice for the manufacturing of wireless monitoring systems for underground infrastructures. Classic waveguide theories developed by Marcatili and Emslie et al. were modified to analyze the transmission of the UHF RFID signal in the waveguide filled with dielectric particulate media. Reasonably good agreement was observed between the measured and calculated power values.

关键词： 射频识别   双向认证协议   混淆函数   二次剩余   形式化分析  

摘要： 射频识别(Radio Frequency Identification,RFID)技术是当今物联网结构中的重要识别技术之一,广泛应用于现代智能家居、智慧城市、智能工业管理和农业环境勘测等领域。然而,RFID系统中采用的无线通信方式引发了一系列安全威胁,包括信道监听、标签或读取器身份伪造、标签跟踪攻击、重放攻击、去同步攻击和前向安全等问题。此外,由于标签体积小且计算资源受限,传统的公钥加密算法和重量级认证协议无法直接应用于RFID系统。为了应对这些挑战并满足市场需求,主要通过在RFID系统中使用轻量级和简单级认证协议,来保障系统的安全性。近年来,研究者提出了一系列轻量级或简单级的双向认证协议。然而,这些安全协议仍存在一些安全问题。因此,研究和发展更加安全可靠的RFID双向认证协议在实际应用方面具有重要的价值意义。本文主要针对轻量级和简单级认证协议展开研究,主要工作如下: (1)对SASI-RH协议进行分析研究,并对其实施了秘密信息披露攻击,证明了不可逆混淆函数在保障协议安全性方面的重要性。并且提出了一种适用于轻量级协议的不可逆的混淆函数Confuse。 (2)针对轻量级协议存在的安全问题,提出了一种基于Confuse混淆函数的轻量级RFID双向认证协议。该协议通过Confuse函数对关键消息进行加密存储,降低关键消息泄露的可能性。在认证过程中,采用伪Hash函数和伪随机数加密的方法,确保认证消息的随机性和新鲜性。通过形式化分析结果表明,该协议能够有效抵御各种攻击手段,满足协议对于安全性的要求。并且相较于同类协议具备更优的传输性能。 (3)在对Vasilakos等人提出的简单级RFID双向认证协议进行研究的基础上,针对其存在的前向安全性问题,提出了一种基于二次剩余算法的简单级RFID双向认证协议。该协议利用离散对数和二次剩余求解的困难性,来确保共享密钥对的安全性。利用模素数下二次剩余的性质,达到协议主体之间相互认证的目的。形式化分析结果表明,该协议能够有效抵御各种攻击手段,满足协议对于安全性的要求。并且,相较于同类协议,该协议具备良好的传输性能。 (4)针对提出的改进协议进行了软件仿真实验。使用socket通信模拟标签、阅读器和后台服务器之间的通信过程,使用Java语言对协议的加密过程进行了实现,并模拟了常见的攻击手段,进一步验证了提出的改进认证协议具有良好的有效性和可靠的安全性。

关键词： 室内定位   超高频射频识别   场景分析算法   标签互耦   接受信号强度指示  

摘要： 由于射频信号极易受到复杂室内环境中多径传播及噪声等因素的影响,场景分析算法凭借其非测距的优势成为目前基于UHF RFID(Ultra High Frequency Radio Frequency Identification,UHF RFID)定位的主流算法之一。但伴随着参考标签部署密度的增加,标签天线互耦影响逐渐增大,成为进一步降低场景分析算法定位精度的关键问题。对此,本文从分析密集部署场景下参考标签反向散射信号特征出发,提出信号扰动模式下点定位和区域定位算法。本文主要工作和创新点包括:(1)搭建包含不同标签间隔距离、方向和数目的RFID实测场景,深入分析引入邻近干扰标签后标签反向散射信号的变化情况,实验结果表明虽然密集部署环境中邻近标签之间的天线互扰对标签反向散射信号具有明显影响,但随着标签间距的增加标签互扰程度会呈现出下降趋势,为扰动模式下定位算法的研究提供可行性基础;(2)提出扰动模式下基于射频信号RSSI(Received signal strength indicator,RSSI)波动特征的点定位算法。该算法与传统基于相似性的场景分析算法不同,本算法将标签波动程度作为邻近参考标签的筛选准则,并引入Kmeans算法利用聚类剔除非邻近参考标签,进一步提高筛选准确性,实验结果表明,在密集部署条件下,本算法明显优于传统场景分析算法k NN算法和修正k NN算法,进一步验证了射频信号波动特征是一项新的有效定位特征;(3)针对货架场景下的区域级定位问题,提出基于单天线的区域级定位算法,FBL算法,该算法通过融合扰动模式下RSSI波动特征和相位波动特征,以进一步提高邻近标签筛选准确性,根据实测结果对比可知,FBL算法能有效提高区域级定位精度,可为智能货架应用提供算法基础。

关键词： RFID   reader coordination   read throughput  

摘要： How to efficiently coordinate multiple readers to work together is critical for high throughput in RFID systems. Existing researchs focus on designing efficient reader scheduling strategies that arrange adjacent readers to work in different time to avoid signal collisions. However, the impact of unbalanced tag number of readers on tag read throughput is still challenging. In RFID systems, the distribution of tags is usually variable and uneven, making the number of tags covered by each reader (i.e., the load) imbalanced. This imbalance leads to different execution time for readers: the heavily loaded readers take longer time to collect all tags, while the other readers whose finish execution earlier have to wait in vain. To avoid this useless waiting and improve the system throughput, this paper focuses on the load balancing problem of multiple readers, which is an NP-hard problem. In this paper, we design heuristic algorithms to adjust readers' interrogation regions and efficiently balance their loads. The amazing advantage of our algorithm is that it can be adopted by almost all existing protocols in multi-reader systems, including the reader scheduling protocol, to improve system throughput. Extensive experiments demonstrate that our algorithm can significantly improve the throughput in various scenarios.