Chipless RFID tags fabricated by fully printing of metallic inks

This paper reviews recent advances in fully printed chipless radio frequency identification (RFID) technology with special concern on the discussion of coding theories, ID generating circuits, and tag antennas. Two types of chipless tags, one based on time-domain reflections and the other based on frequency domain signatures, are introduced. To enable a fully printed encoding circuit, linearly tapering technique is adopted in the first type of tags to cope with parasitic resistances of printed conductors. Both simulation and measurement efforts are made to verify the feasibility of the eight-bit fully printed paper-based tag. In the second type of tags, a group of LC tanks are exploited for encoding data in frequency domain with their resonances. The field measurements of the proof-of-concept of the tag produced by toner-transferring process and flexible printed circuit boards are provided to validate the practicability of the reconfigurable ten-bit chipless RFID tag. Furthermore, a novel RFID tag antenna design adopting linearly tapering technique is introduced. It shows 40 % save of conductive ink materials while keeping the same performance for conventional half-wave dipole antennas and meander line antennas. Finally, the paper discusses the future trends of chipless RFID tags in terms of fabrication cost, coding capacity, size, and reconfigurability. We see that, coupled with revolutionary design of low-cost tag antennas, fabrication/reconfiguration by printing techniques, moving to higher frequencies to shrink tag sizes and reduce manufacturing cost, as well as innovation in ID generating circuits to increase coding capacities, will be important research topics towards item-level tracking applications of chipless RFID tags.     

IR-UWB-based chipless RFID system

This paper presents a chipless radio frequency identification (RFID) system, based on impulse radio ultra-wideband (IR-UWB) technology. This UWB-RFID system consists of a transmitter, a receiver, two tapered slot antennas, and several chipless tags. Covering the lower UWB frequency band in 3–5 GHz, the transmitter integrated circuit generates signals with high peak-to-peak amplitude of 6.6 V and short pulse duration of 1 ns. The receiver front end consists of amplifiers and filters, with total front-end gain up to 36 dB. This is followed by an equivalent time sampling analog to digital converter to sample the equivalent RF signals directly followed by digital signal processing in MATLAB. The tapered slot antenna has a high and relatively flat gain of 10 dBi. The chipless tag is uniplanar and with a size of 23 × 23 × 0.508 mm³ only. Based on these hardware designs developed in our research group, a novel method is proposed to separate two overlapped time-domain signals. This method, which is experimentally validated in this paper, greatly simplifies the hardware designs, especially the chipless tag. This chipless UWB-RFID system is an excellent candidate to realize a low-cost, low-power, and high-performance system for next-generation RFID applications.     

Design rules for chipless RFID tags based on multiple scatterers

In this paper, we present some design rules to create a chipless RFID tag that encodes the information in the frequency domain. Some criterions are introduced to make the best choice concerning the elementary scatterers that act like signal processing antennas. The performance of several scatterers will be compared before a study on the radiating properties of a versatile C-like scatterer. An electrical model as well as a transfer function model is presented to best understand the frequency response of both a single-layer and a grounded scatterer. An example of the design and the optimization of a chipless RFID tag based on the use of multiple scatterers are provided, and the frequency optimization step for each resonant peak will be discussed.     

基于极点展开法无芯片电子标签的识别与传感

利用极点展法得到的极点与留数,可对无芯片电子标签进行识别与传感.由极点与标签结构成对应关系,利用衰减因子与谐振频率可对标签结构的基本属性进行识别,还可以进一步地感知标签结构的弯曲变形程度;利用留数所含有的信息,可以感知标签结构相对入射波或观测点的空间角度方位信息.通过理论仿真分析,极点与留数不仅可用来识别标签,还可以感知标签结构的其它特性的功能.     

A practical quadratic residues based scheme for authentication and privacy in mobile RFID systems

In this paper we propose a novel approach to authentication and privacy in mobile RFID systems based on quadratic residues and in conformance to EPC Class-1 Gen-2 specifications. Recently, Chen et al. (2008) [10] and Yeh et al. (2011) [11] have both proposed authentication schemes for RFID systems based on quadratic residues. However, these schemes are not suitable for implementation on low-cost passive RFID tags as they require the implementation of hash functions on the tags. Consequently, both of these current methods do not conform to the EPC Class-1 Gen-2 standard for passive RFID tags which from a security perspective requires tags to only implement cyclic redundancy checks (CRC) and pseudo-random number generators (PRNG) leaving about 2.5k–5k gates available for any other security operations. Further, due to secure channel assumptions both schemes are not suited for mobile/wireless reader applications. We present the collaborative authentication scheme suitable for mobile/wireless reader RFID systems where the security of the server–reader channel cannot be guaranteed. Our schemes achieves authentication of the tag, reader and back-end server in the RFID system and protects the privacy of the communication without the need for tags to implement expensive hash functions. Our scheme is the first quadratic residues based scheme to achieve compliance to EPC Class-1 Gen-2 specifications. Through detailed security analysis we show that the collaborative authentication scheme achieves the required security properties of tag anonymity, reader anonymity, reader privacy, tag untraceability and forward secrecy. In addition, it is resistant to replay, impersonation and desynchronisation attacks. We also show through strand space analysis that the proposed approach achieves the required properties of agreement, originality and secrecy between the tag and the server.     

A Novel RFID Tag Identification Protocol: Adaptive n-Resolution and k-Collision Arbitration

Since radio frequency identification (RFID) technology has become increasingly common in numerous applications, including large-scale supply chain management, improving the efficiency of RFID tag identification is an important task. In practical settings, the identification of RFID tags often occurs in a dynamic environment, in which tags move through a specific interrogation range. However, the literature contains few studies on the design of efficient identification protocols in dynamic environments. This study proposes a novel tag identification protocol that is particularly efficient in dynamic environments. the proposed protocol involves two anti-collision techniques: adaptive n-Resolution (AnR) and k-Collision Arbitration (kCA). These two techniques significantly improve the tag identification delay and communication overhead. This improvement is primarily due to the use of a newly designed challenge-response bit sequence mechanism and the information obtained from the previous tag identification procedure. As a result, AnR requires only a constant number of interrogation times regardless of the number of target tags, while kCA further improves the efficiency of tag identification with \(k\) -splitting collision arbitration. Rigorous analysis and simulation experiments show that this tag identification protocol significantly outperforms related methods (by at least 48.85 % identification delay and 23.87 % communication overhead can).     

基于混合编码的射频识别无芯片标签设计

为降低传统射频识别标签成本,提升标签编码容量,文中采用幅值与频率位置混合编码的方法,设计了一种由微带主传输线、收发正交的超宽带天线和长度不等的谐振器组成的,具有大容量编码功能的无芯片射频识别标签。仿真及测试结果表明,该标签在2.376.17 GHz频段上得到了20 bit的编码容量,混合编码后可得到60 bit的编码容量。实测3种编码状态的8 bit无芯片标签,显示谐振器频点误差小于10 MHz,能够保证谐振点的准确识别,实现预设的编码功能。该种具有大容量编码功能无芯片标签,降低了物联网系统的成本,可以取代激光条形码应用于物流领域。     

Phase-Encoded Chipless RFID Transponder for Large-Scale Low-Cost Applications

A novel 3 b chipless RFID transponder is presented. The transponder comprises three microstrip patch antennas, which are loaded with open circuited (O/C) high impedance stubs. The antennas are resonant at nearby frequencies, and when excited with their respective resonant frequency signals, they re-radiate backscattered signals with distinct phase characteristics. This phase information is encoded as hexadecimal bits for the proposed chipless RFID tag. Both the CST Microwave Studio full-wave solver and the anechoic chamber measurements show a 30$^{circ}$ phase step for the 3 b chipless RFID transponder. It it easily transferred to printed technology, and it may find applications in the mass identification market.      

A 13.56-MHz RFID System Based on Organic Transponders

RFID tags based on organic transistors are described, discussing in detail the IC blocks used to build the logic and the radio. Tags energized and read out at 13.56 MHz, de facto standard frequency for item-level identification, have been tested and enabled for the first time multiple-object identification, using different 6-bit codes. A complete 64-bit transponder, the most complex organic RFID tag reported to date, operates at 125 kHz and employs 1938 transistors     

Design of a RFID System for Real-Time Tracking of Laboratory Animals

In this paper, a real-time RFID system capable of tracking laboratory animals is designed and implemented. Four passive RFID tags based on low frequency are designed and implemented. The tags can be read by any RFID reader that operates on the low frequency range 125–134 kHz. The tags are designed through the investigation of various antenna, encoding, modulation, and energy harvesting techniques. The tag receives the electromagnetic signal via the antenna, and converts it to a DC signal that the microcontroller can use to manipulate the electromagnetic signal with the data such that the reader can decode the unique tag identifier. RFID sensors are designed and implemented to collect data from various monitored areas of a semi natural environment. The data is sent to a central data coordinator for pre-processing and middleware for data error checking, display and storage. The RFID system can successfully detect and store movement data in real time. A read range of 14.5 cm is achieved.     

ASAF ALOHA Protocol for Dense RFID Systems

RFID tags are used for varied applications in large numbers. Human Tracking is one such important application wherein the RFID system detects the presence of a tag in a dense tag environment. Quick estimation of the number of tags in the field at a desired level of accuracy is one of the most common requirements in the present scenario. Identification of tags has become a critical area which need more time and unsuitable in many situations; especially where tag set is dense. We introduce a novel medium access control (MAC) protocol for Radio Frequency IDentification (RFID) systems which exploits the statistical information collected at the reader. The protocol, termed Adaptive Slot Adaptive Frame (ASAF) ALOHA protocol, is motivated to significantly improve the total read time performance of the currently suggested MAC protocols for RFID systems by minimizing the collisions of the tags. In order to perform this task, ASAF estimates the dynamic tag population and adapts the frame size and number of slots simultaneously in the subsequent round via a simple policy that maximizes an appropriately defined function. We demonstrated that ASAF is better than the current RFID MAC protocols. We also considered the case where suddenly if the number of tags increases, the running frame with adapted slots gets flushed away and new frame with increased number of slots gets adapted automatically by the system showing the robustness in this case as well.     

基于FM0记忆辅助特性的RFID标签碰撞检测

为实现两个射频识别(RFID)碰撞标签信息的检测和分离,提出一种利用Gen2标准中FM0标签编码固有记忆特性的检测方法。通过对FM0比特编码特点和碰撞标签信息的无记忆检测分析,得到基于单个比特持续时间的无记忆检测方法的条件错误概率和单个标签信息检测的误码率;然后利用单个FM0比特编码需要前一比特的“记忆”特性,得到对应于前一比特的一对测量值和对应于下一比特的一对测量值,进而得到碰撞标签信息的1比特记忆辅助检测时的条件错误概率和误码率性能;并对在帧Aloha媒质接入方案中采用提出的检测方法时的N个标签群的总延迟减少性能进行了分析。仿真实验结果表明,提出的1比特记忆辅助检测方法,相比于无记忆检测具有更好的误码率性能,且能减少标签群接入时的总延迟。     

Protecting Your Privacy with a Mobile Agent Device in RFID Environment

Radio Frequency Identification (RFID) Technology is a contactless automatic identification technology using radio frequency. For this RFID technology to be widely spread, the problem of privacy invasion should be solved. There are many research works in progress to solve the RFID privacy problems. Most of works for solving this problem have focused on developing light-weight cryptographic modules which can be embedded into RFID tags, but some of them used a proxy agent approach that control communications between the tag and the reader for protecting user privacy. The later approach is very useful and practical in terms of manufacturing low-cost tag hardware. However, all schemes of this approach have some problems in ownership transfer and forgery detection. In this paper, we are focusing on the proxy agent approach and we suggest an advanced agent scheme that guarantees not only privacy protection but also forgery detection. And our scheme is more scalable than other agent schemes so far.     

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).     

Optimization of an RFID location identification scheme based on the neural network

An indoor localization technology is increasingly critical as location‐aware applications evolve. Researchers have proposed several indoor localization technologies. Because most of the proposed indoor localization technologies simply involve using the received signal strength indicator value of radio‐frequency identification (RFID) for indoor localization, radio‐frequency interference, and environmental factors often limit the accuracy of localization results. Therefore, this study proposes an accurate RFID localization based on the neural network (ARL‐N²), a passive RFID indoor localization scheme for identifying tag positions in a room, combining a location identification based on dynamic active RFID calibration algorithm with a backpropagation neural network (BPN). The proposed scheme composed of two phases: in the training phase, an appropriate BPN architecture is constructed using the training data derived from the coordinates of reference tags and the coordinates obtained using the localization algorithm. By contrast, the online phase involves calculating the tracking tag coordinates and using these values as BPN inputs, thereby enhancing the estimated location. A performance evaluation of the ARL‐N² schemes confirms its high localization accuracy. The proposed method can be used to locate critical objects in difficult‐to‐find areas by creating minimal errors and applying and economical technique. Copyright © 2013 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.     

射频识别动态定位方法

提出一种新型的通过参考标签和移动RFID射频读写器进行定位的方法。该定位方法的主要优点是不需要记录任何测量信息如TOA、RSSI等,而是通过移动读写器,不断对目标标签和参考标签进行读取,经椭圆还原算法对读区域进行还原,最终以交集计算实现定位。该方法思路简单,但实现了较高精度的RFID室内定位。实验结果表明,该定位方法的精度可在最小的参考标签单元格内（可到达数十厘米级）。同时建立的原型定位系统具有成本低、易于部署等特点,存在应用于大规模RFID仓储定位管理的可行性。     

Maximum Likelihood Approach for RFID Tag Set Cardinality Estimation with Detection Errors

Estimation schemes of Radio Frequency IDentification (RFID) tag set cardinality are studied in this paper using Maximum Likelihood (ML) approach. We consider the estimation problem under the model of multiple independent reader sessions with detection errors due to unreliable radio communication links and/or collisions. In every reader session, both the detection error probability and the total number of tags are estimated. In particular, after the $R$ -th reader session, the number of tags detected in $j$ ( $j=1,2,...,R$ ) reader sessions out of $R$ sessions is updated, which we call observed evidence. Then, in order to maximize the likelihood function of the number of tags and the detection error probability given the observed evidences, we propose three different estimation methods depending on how to treat the discrete nature of the tag set cardinality. The performance of the proposed methods is evaluated under different system parameters and compared with that of the conventional method via computer simulations assuming flat Rayleigh fading environments and framed-slotted ALOHA based protocol.     

Group delay modulation for pulse position coding based on periodically coupled C-sections

Chipless radio frequency identification (RFID) is an emerging research area nowadays. The recent development in this area proves its efficiency to compete with low cost identification systems like barcodes in the upcoming years. Chipless RFID encodes data using different kinds of spectral signature produced from some planar images as in the case of barcodes, the difference here is those images are made with conductive materials. Among the different ways of information encoding, a powerful way of encoding is time domain approach. This paper incorporates a tag using group delay encoding. The proposed chipless tag is composed of commensurate cascaded transmission line sections coupled at alternative ends (also known as C-sections). It consists of single group of C-sections. However, in order to increase the coding capacity, the proposed tag can allow multi-frequencies also. In addition to this, the tag is also compatible with commercial ultra wide band radar. The proposed tag is validated experimentally. It exhibits a good reading range of 1.2 m.     

Tree-LSHB+: An LPN-Based Lightweight Mutual Authentication RFID Protocol

In this paper, we propose an enhancement of the Tree-based authentication protocol, named as the Tree-LSHB+ protocol. The protocol is a lightweight authentication protocol that is suitable for use in radio frequency identification (RFID) systems. Compared with the Tree-based HB authentication protocol, our protocol provides mutual authentication in authentication stage. The authentication keys stored in the reader and the tag are also updated when the mutual authentication succeeds. It means that two drawbacks can be avoided in the Tree-based authentication protocol, one is that only the reader authenticates the tag and the other is that the secret keys stored in the tags remain unchanged all the time. We also improve the performance of Tree-based protocol with the property of Toeplitz matrix and find that the Tree-LSHB+ protocol is still a good choice for RFID authentication.