To reduce RFID tag identification delay, we propose a novel Dynamic Splitting protocol (DS) which is an improvement of the Query tree protocol (QT). DS controls the number of branches of a tree dynamically. An improved performance of DS relative to QT is verified by analytical results and simulation studies.

Tracking a large quantity of moving target tags simultaneously is essential for the localization and guidance of people in welfare facilities like hospitals and sanatoriums for the aged. The locating system using active RFID technology consists of a number of fixed RFID readers and tags carried by the target objects, or senior people. We compare the performances of several determination algorithms which use the power measurement of received signals emitted by the moving active RFID tags. This letter presents a study on the effect of collision in tracking large quantities of objects based on active RFID real time location system (RTLS). Traditional trilateration, fingerprinting, and well-known LANDMARC algorithm are evaluated and compared with varying number of moving tags through the SystemC-based computer simulation. From the simulation, we show the tradeoff relationship between the number of moving tags and estimation accuracy.

In this paper we propose a novel RFID anti-collision technique that intelligently combines polling and random access schemes. These two fundamentally different medium access control protocols are coherently integrated in our design while functionally complementing each other. The polling mode is designed to enable fast collision-free identification for the tags that exist within reader's coverage across the sessions. In contrast, the random access mode attempts to read the tags uncovered by the polling mode. Our proposed technique is particularly suited for a class of RFID applications in which a stationary reader periodically attempts to identify the tags with slow mobility. Numerical results show that our proposed technique yields much faster identification time against the existing approaches under various operating conditions.

The performance of a UHF-band passive RFID system in a dense multi-reader environment is limited by both the reader-to-reader interference and reader-to-tag interference. In this paper, first, we propose a combination of subcarrier modulation backscattering and reduced carrier frequency offset among readers to reduce both the reader-to-reader interference and the reader-to-tag interference. Then, we propose a new distributed modulation index control scheme using the readers' estimation of the tag's SINR in order to further reduce the reader-to-tag interference. By adaptively controlling each reader's transmission modulation index, the asymmetric reader-to-tag interference can be effectively controlled to satisfy the required SINR of tags. Computer simulations show that the proposed scheme can reduce the minimum required inter-reader distance or increase the number of concurrently operable readers in dense multi-reader environments, especially when there are large differences in the levels of reader-to-tag interference. We show some optimizations of the proposed scheme for practical RFID applications. We also propose a bandwidth efficient modulation scheme for reader transmission which is suitable for the proposed modulation index control scheme.

In RFID systems, collision resolution is a significant issue in fast tag identification. This letter presents a dynamic frame-slotted ALOHA algorithm that uses a collision factor (DFSA-CF). This method enables fast tag identification by estimating the next frame size with the collision factor in the current frame. Simulation results show that the proposed method reduces slot times Required for RFID identification. When the number of tags is larger than the frame size, the efficiency of the proposed method is greater than those of conventional algorithms.

In this letter, we propose a new scheme for the tag structure of the EPCglobal Class-1 Generation-2 (EPC C1 Gen2) standard equipped with a channel encoding block and the corresponding decoding block in the receiver of the reader system. The channel coded tag is designed to fully accommodate the EPC C1 Gen2 standard. The use of the proposed channel encoding block increases the number of logic gates in the tag by no more than 5%. The proposed reader system is designed to be used in the mixed tag modes as well, where the channel coded tags and existing tags co-exist in the same inventory round. The performances of the proposed tags and the corresponding reader systems are also presented by comparing the number of EPC error frames and the tag identification time with those of the conventional tags and reader systems.

A high-efficiency CMOS rectifier circuit for UHF RFID applications was developed. The rectifier utilizes a self-Vth-cancellation (SVC) scheme in which the threshold voltage of MOSFETs is cancelled by applying gate bias voltage generated from the output voltage of the rectifier itself. A very simple circuit configuration and zero power dissipation characteristics in biasing enable excellent power conversion efficiency (PCE), especially under small RF input power conditions. At higher RF input power conditions, the PCE of the rectifier automatically decreases. This is the built-in self-power-regulation function. The proposed SVC CMOS rectifier was fabricated with a 0.35-µm CMOS process and the measured performance was compared with those of conventional nMOS, pMOS, and CMOS rectifiers and other types of Vth cancellation rectifiers as well. The SVC CMOS rectifier achieves 32% of PCE at the -10 dBm RF input power condition. This PCE is larger than rectifiers reported to date under this condition.

A single chip NFC transceiver with Dual Antenna structure supporting not only NFC active and passive mode but also 13.56 MHz RFID reader and tag mode is designed and fabricated. The proposed NFC transceiver can operate as a RFID tag even without external power supply thanks to a dual antenna structure for initiator and target. The area increment due to additional target antenna is negligible because the target antenna is constructed by using a shielding layer of the initiator antenna.

In this study we propose a manufacturing control framework based on radio-frequency identification (RFID) technology and a distributed information system to construct a mass-customization production process in a loosely coupled shop-floor control environment. On the basis of this framework, we developed RFID middleware and an integrated information system for tracking and controlling the manufacturing process flow. A bicycle manufacturer was used to demonstrate the prototype system. The findings of this study were that the proposed framework can improve the visibility and traceability of the manufacturing process as well as enhance process quality control and real-time production pedigree access. Using this framework, an enterprise can easily integrate an RFID-based system into its manufacturing environment to facilitate mass customization and a just-in-time production model.

In an RFID search protocol, a reader uses a designated query instead of an unspecified query commonly used in RFID authentication protocols. Due to this fundamental difference, techniques used in RFID authentication protocols may not be suitable for RFID search protocols. Tan et al.'s protocol, however, is based on techniques used in previous works such as using random values. In this paper, we propose two RFID search protocols, one based on static ID and the other based on dynamic ID, both which does not require additional measures to satisfy security requirements of RFID protocols. We achieve this by using counters.

In this paper, we design and implement a multi-protocol 13.56 MHz reader in software. In order to satisfy the timing constraint, three level optimizations called compile level, syntax level, and architectural level optimizations are applied. The execution time of optimized code is reduced by 85%, so that it satisfies timing requirement of a 60 MHz speed EISC processor. In addition, the binary code size is minimized to 211 KBytes which can be loaded on a 256 KB size memory.

RFID event filtering is an important issue of RFID data management. Tag read events from readers have some problems like unreliability, redundancy, and disordering of tag readings. Duplicated events lead to performance degradation of RFID systems with a flood of similar tag information. Therefore, this paper proposes a fuzzy logic-based quantized event filter. In order to reduce duplicated tag readings and solve disordering of tag readings, the filter applies a fuzzy logic system to control a filtering threshold by the change in circumstances of readers. Continuous tag readings are converted into discrete values for event generation by the filtering threshold. And, the filter generates as many events as the discrete values at a point of event generation time. Experimental results comparing the proposed filter with existing RFID event filters, such as the primitive event filter and the smoothing event filter, verify effectiveness and efficiency of the fuzzy logic-based quantized event filter.

The RFID (Radio Frequency IDentification) tag technology is expected as a tool of localization. By the localization of RFID tags, a mobile robot which installs in RFID readers can recognize surrounding environments. In addition, RFID tags can be applied to a navigation system for walkers. In this paper, we propose an adaptive likelihood distribution scheme for the localization of RFID tags. This method adjusts the likelihood distribution depending on the signal intensity from RFID tags. We carry out the performance evaluation of estimated position error by both computer simulations and implemental experiments. We show that the proposed system is more effective than the conventional system.

Recent advancements in the ubiquitous sensor network field have brought considerable feasibility to the realization of a ubiquitous society. A ubiquitous sensor network will enable the cooperative gathering of environmental information or the detection of special events through a large number of spatially distributed sensor nodes. Thus far, radio frequency identification (RFID) as an application for realizing the ubiquitous environment has mainly been developed for public and industrial systems. To this end, the most existing applications have demanded low-end antennas. In recent years, interests of ubiquitous sensor network have been broadened to medical body area networks (BAN), wireless personal area networks (WPAN), along with ubiquitous smart worlds. This increasing attention toward in ubiquitous sensor network has great implications for antennas. The design of functional antennas has received much attention because they can provide various kinds of properties and operation modes. These high-end antennas have some functions besides radiation. Furthermore, smart sensor nodes equipped with cooperated high-end antennas would allow them to respond adaptively to environmental events. Therefore, some design approaches of functional antennas with sensing and reconfigurability as high-end solution for smart sensor node, as well as low-end antennas for mobile RFID (mRFID) and SAW transponder are presented in this paper.

There are many protocols proposed for protecting Radio Frequency Identification (RFID) system privacy and security. A number of these protocols are designed for protecting long-term security of RFID system using symmetric key or public key cryptosystem. Others are designed for protecting user anonymity and privacy. In practice, the use of RFID technology often has a short lifespan, such as commodity check out, supply chain management and so on. Furthermore, we know that designing a long-term security architecture to protect the security and privacy of RFID tags information requires a thorough consideration from many different aspects. However, any security enhancement on RFID technology will jack up its cost which may be detrimental to its widespread deployment. Due to the severe constraints of RFID tag resources (e.g., power source, computing power, communication bandwidth) and open air communication nature of RFID usage, it is a great challenge to secure a typical RFID system. For example, computational heavy public key and symmetric key cryptography algorithms (e.g., RSA and AES) may not be suitable or over-killed to protect RFID security or privacy. These factors motivate us to research an efficient and cost effective solution for RFID security and privacy protection. In this paper, we propose a new effective generic binary tree based key agreement protocol (called BKAP) and its variations, and show how it can be applied to secure the low cost and resource constraint RFID system. This BKAP is not a general purpose key agreement protocol rather it is a special purpose protocol to protect privacy, un-traceability and anonymity in a single RFID closed system domain.

UHF radio frequency identification (RFID) has gathered significant interest in the field of long-distance automatic identification applications. Since UHF RFID shares the frequency band with other RFID and/or other wireless systems, it is important to determine how much interference can be applied without causing a significant degradation of anti-collision speed. In this paper, the permissible link quality for RFID anti-collision in a practical environment is discussed by considering an erroneous communication link, taking into account of bit encoding and the type of interference. We approach the quantification of permissible link quality experimentally along with protocol simulations and the mathematical analyses. An international standard protocol, employing frame slotted ALOHA, was used as the air protocol. For these investigations, the present authors developed a protocol simulator. The simulation results were compared with analytical values based on Poisson distribution. The investigation in the return (tag to reader) link, and the forward (reader to tag) link, were analyzed separately. As result of the protocol simulation, it is generally important to secure the Pulse Error Rate 10-4 or better in both return and forward links for the anti-collision of 64 or less tags. The quality of the return link may be relaxed when the application does not require fast anti-collision. The degradation of the forward link, on the other hand, may entail loss of important commands, resulting in extremely slow anti-collision. It is measured experimentally that the required link quality can be relaxed by up to 10 dB in the return links and by 5 dB in the forward link when the primary source of interference originates in the interfering readers.

Tag collision is a major problem in the field of multi-tag identification in RFID systems. To solve this problem, many RFID systems adopt their own collision arbitration algorithms based on framed-structure slotted Aloha (FSSA) due to the simplicity of implementation. The frame size, meaning the number of slots in a frame, is a very important factor to inventory tags' responses in the FSSA. How to assign the frame size is therefore crucial to the collision arbitration performance. Since the existing collision arbitration methods do not consider the slot times of each slot when assigning frame size, they may increase overall identification time. By involving the slot times, we improve the collision arbitration performance of the conventional methods. Simulation results show that collision arbitration based on the proposed method is superior to that based on the conventional methods, irrespective of the number of tags.

Binary search tree and framed ALOHA algorithms are commonly adopted to solve the anti-collision problem in RFID systems. In this letter, the read efficiency of these two anti-collision algorithms is compared through computer simulations. Simulation results indicate the framed ALOHA algorithm requires less total read time than the binary search tree algorithm. The initial frame length strongly affects the uplink throughput for the framed ALOHA algorithm.

For the success of a large deployment of UHF RFID, easy-to-use and low-cost engineering tools to facilitate the performance evaluation are demanded particularly in installations and for trouble shooting. The measurement of interrogation area is one of the most typical industrial demands to establish the stable readability of UHF RFID. Exhaustive repetition of tag position change with a read operation and a usage of expensive measurement equipment or special interrogators are common practices to measure the interrogation area. In this paper, a practical method to measure the interrogation area of a UHF RFID by using a battery assisted passive tag (BAP) is presented. After introducing the fundamental design and performances of the BAP that we have developed, we introduce the measurement method. In the method, the target tag in the target installation is continuously traversed either manually or automatically while it is subjected to a repetitive read of a commercial interrogator. During the target tag traversal, the interrogator's commands are continuously monitored by a BAP. With an extensive analysis on interrogator commands, the BAP can differentiate between its own read timings and those of the target tag. The read timings of the target tag collected by the BAP are recorded synchronously with the target tag position, yielding a map of the interrogation area. The present method does not entail a measurement burden. It is also independent of the choice of interrogator and tag. The method is demonstrated in a practical UHF RFID installation to show that the method can measure a 40 mm resolution interrogation area measurement just by traversing the target tag at a slow walking speed, 300 mm/sec.

A low-ripple diode charge-pump type AC-DC converter based on the Cockcroft-Walton diode multiplier is proposed for coil-coupled passive IC tags in this paper. This circuit is developed as a power supply for passive RFID tags with smart functions such as heart rate detection and/or body temperature measurement. The proposed circuit converts wirelessly induced power to a low-ripple DC voltage suitable for a 13.56 MHz RFID tag. The proposed circuit topology and the principle of operation are explained and treated theoretically by using quasi-equivalent small-signal models. The proposed circuit was implemented on a PCB. And it was confirmed that the proposed circuit provides 3.3 V DC with a ripple of less than 20 mV when a 4 Vp-p sinusoidal input is applied. Under this condition, the maximum output power is about 310 µW. The measured results were in good agreement with theoretical and HSPICE simulation results.