This paper presents a simulation based method to predict the amount of frequency interference in a passive type RFID system. To judge occurrence of frequency interference, we use a parameter POI (probability of interference) that depends on several factors such as multiple access method, emission mask, the number of channel, etc. Due to its dependence on several factors, a Monte-carlo based simulation is suitably used. Through the simulation, we draw minimum separation distance between two readers and examine performance degradation due to aggregate interfering readers. Moreover, we present a reader deployment strategy based on the average POI of active readers operating in some area.

In this Letter, we investigate the correlation rate of a random sequence data set which is collected by RFID (Radio Frequency IDentification) readers in an indoor location. Using a passive RFID tag introduces reading error, which causes a loss of original data. From the question of how sensing errors of RFID readers affect the location prediction algorithm used for context awareness services at home, we analyze the correlation rate of a collected data set with respect to RFID reader-sensing error rate. Through our analysis, we conclude that the prediction accuracy can be better or worse than the one of the original data streams according to the error rate. We suggest that the reader specification has to be satisfied by the error boundary which is found in this work for the tolerant location prediction.

The collision of ID signals from a large number of co-located passive RFID tags is a serious problem; to realize a practical RFID systems we need an effective anti-collision algorithm. This letter presents an adaptive algorithm to minimize the total time slots and the number of rounds required for identifying the tags within the RFID reader's interrogation zone. The proposed algorithm is based on the framed ALOHA protocol, and the frame size is adaptively updated each round. Simulation results show that our proposed algorithm is more efficient than the conventional algorithms based on the framed ALOHA.

A full wave voltage multiplier for passive RFID transponders is presented. The current driving capability of the proposed rectifier is remarkably improved at the cost of only a small increase in layout area compared to the widely used conventional half wave voltage multiplier. The communication distance of RFID systems can be extended due to the improved RF carrier to DC power conversion capability of the proposed voltage multiplier.

Implementation of RFID reader/writer on software defined radio is studied in this paper. The target RFID is ISO18000-3 mode 2 which has 8 reply channels for simultaneous communication with 8 different RFID tags. In the software defined radio architecture, the 8 reply channels are sampled at a single A/D converter and separated by digital down converters, whereas conventional RFID architecture has redundant 8 parallel analog down converters. A novel multi-stage transmultiplexing digital down converter is proposed for efficient implementation of multi-channel digital down converter. Moreover the proposed architecture is implemented on a FPGA evaluation board, and validity of the system is confirmed on a real hardware. The proposed architecture can be applied to multi-channel receiver for dynamic spectrum system in the cognitive radio.

Eavesdropping on backward channels in RFID environments may cause severe privacy problems because it means the exposure of personal information related to tags that each person has. However, most existing RFID tag security schemes are focused on the forward channel protections. In this paper, we propose a simple but effective method to solve the backward channel eavesdropping problem based on Randomized-tree walking algorithm for securing tag ID information and privacy in RFID-based applications. In order to show the efficiency of the proposed scheme, we derive two performance models for the cases when CRC is used and not used. It is shown that the proposed method can lower the probability of eavesdropping on backward channels near to '0.'

We have been investigating a new class of ubiquitous services, called Activity Logging, which takes advantage for private and public sensors and the RFID tags on real-world objects. The purpose of Activity Logging is to digitally record users' interests with real-world objects and users' context to describe the users' activity. Such digital information acquired from a range of sensors and tags, if being accumulated, forms a great data source for users to recall their activities later or to share the activities with others. This paper explores the design space to realize Activity Logging, and proposes a simple mobile device called Activity Recorder that marries public and private sensors to provide a powerful Activity Logging service. An Activity Recorder contains a range of private sensors, and has communication capability to work with public sensors around the user.

Many devices are expected to be networked with wireless appliances such as radio frequency identification (RFID) tags and wireless sensors, and the number of such appliances will greatly exceed the number of PCs and mobile telephones. This may lead to an essential change in the network architecture. This paper proposes a new network architecture called the appliance defined ubiquitous network (ADUN), in which wireless appliances will be networked without network protocol standards. Radio space information rather than individual appliance signals is carried over the ADUN in the form of a stream with strong privacy/security control. It should be noted that this is different from the architectural principles of the Internet. We discuss a network-appliance interface that is sustainable over a long period, and show that the ADUN overhead will be within the scope of the broadband network in the near future.

The performance of a passive RFID system in a dense multi-reader environment is limited by both reader-to-reader interference and reader-to-tag interference. In this paper, we formulate a practical RFID system model which takes into account the non-linear demodulation of the tags and the transmission spectrum of the readers. Using this model, we derive a novel linear programming formulation to obtain the optimum communication probability of the readers for a given reader deployment scenario. We then propose two novel distributed interference avoidance algorithms based on the detect-and-abort principle for multi-channel readers which can effectively mitigate the reader-to-tag interference as well as the reader-to-reader interference. Computer simulations show that the proposed algorithms can improve the successful communication probability and fairness among readers in dense reader environments, compared with the conventional listen-before-talk algorithm.

This work is concerned with the problem of robot localization using standard RFID tags as landmarks and an RFID reader as a landmark sensor. A main advantage of such an RFID-based localization system is the availability of landmark ID measurement, which trivially solves the data association problem. While the main drawback of an RFID system is its low spatial accuracy. The result in this paper is an improvement of the localization accuracy for a standard short-range RFID sensor. One of the main contributions is a proposal of a machine learning approach in which multiple classifiers are trained to distinguish RFID-signal features of each location. Another contribution is a design tool for tag arrangement by which the tag configuration needs not be manually designed by the user, but can be automatically recommended by the system. The effectiveness of the proposed technique is evaluated experimentally with a real mobile robot and an RFID system.

This paper proposes a novel method to suppress tag collision in the ISO 18000-6 type B protocol which is one of the standard protocols of UHF RFID systems. The anti-collision performance in terms of the total identification time is improved by reducing the length of bits and the number of transmission commands required for multi-tag identification in the ISO 18000-6 type B protocol. Simulation results show that the proposed method improves the multi-tag identification time by about 15% over the conventional method, irrespective of the number of tags.

An integrated multi-level simulation environment is developed for a highly collision-resistant RFID system. An analog/mixed-signal (AMS) simulator for a circuit-level description of analog front-end power/signal transmission through electro-magnetic coupling is concurrently connected to a tailored software simulator for system-level description of digital back-end processing of TH-CDMA based anti-collision communication. The feasibility of the RFID system in which more than 1,000 transponders can be identified by a single reader in 400 msec is successfuly explored, under a practical presence of field disturbances such as background noises in communication channels as well as variations of electro-magnetic coupling strengths for power transmission.

A circuit design of a CMOS integrable heartbeat spike-pulse detection circuit is proposed in this paper. This circuit is developed to be implemented on a small-sized RFID sensor tag (which we call a smart RFID tag throughout this paper) implanted in a transgenic mouse. This circuit can detect only spike pulses with magnitude higher than the prescribed level from a mouse's heartbeat signal, which is sensed by a small microphone sensor and/or an electrocardiogram (ECG) microsensor attached to the RFID tag. The proposed circuit features robustness to the device tolerances and temperature variations thanks to its auto-bias technique based on good device matching and its switched-capacitor auto offset-canceling technique. The circuit was fabricated by a standard 0.35 µm CMOS process and works at a supply voltage of 3 V and dissipates less than 800 µW.

Radio frequency identification (RFID) technology is becoming increasingly attractive because of its high storage capacity and reprogrammability. There is a challenge to be overcome when a reader needs to read a number of tags within the reader's interrogation zone at the same time. In this paper, we present an anti-collision scheme in a RFID system. The scheme is based on the dynamic framed ALOHA protocol developed for radio networks. In our scheme, we propose two methods to estimate the number of tags. Simulation results indicate that the total number of time slots for reading all tags is about 4 times the number of tags that need to be read, including acknowledgement time slots. The main advantages of our scheme are the great performance of uplink throughput and its easy implementation for both readers and tags.

A highly collision-resistive RFID system multiplexes communications between thousands of transponders and a single reader using TH-CDMA based anti-collision scheme. This paper focuses on the back-end design consideration of such an RFID system with the deployment of high-level modeling techniques, accompanying a technical comparison of physical-level description, hardware-based emulation, and software-based simulation. A new rapid-prototyping simulation system was constructed to evaluate the robustness of a multiplexed RFID link system with more than 1,000 channels in the presence of field disturbances, and the design parameters of the back-end digital signal processing that dominated anti-collision performance were explored. Finally, the derived optimum parameters were applied to the design of a back-end digital integrated circuit to be installed in collision-resistive transponder circuitry.

A highly collision-resistive RFID system multiplexes communications between thousands of tags and a single reader in combination with time-domain multiplexing code division multiple access (TD-CDMA), CRC error detection, and re-transmission for error recovery. The collision probability due to a random selection of CDMA codes and TDMA channels bounds the number of IDs successfully transmitted to a reader during a limited time frame. However, theoretical analysis showed that the re-transmission greatly reduced the collision probability and that an ID error rate of 2.510-9 could be achieved when 1,000 ID tags responded within a time frame of 400 msec in ideal communication channels. The proposed collision-resistive communication scheme for a thousand multiplexed channels was modeled on a discrete-time digital expression and an FPGA-based emulator was built to evaluate a practical ID error rate under the presence of background noise in communication channels. To achieve simple anti-noise communication in a multiple-response RFID system, as well as unurged re-transmission of ID data, adjusting of correlator thresholds provides a significant improvement to the error rate. Thus, the proposed scheme does not require a reader to request ID transmission to erroneously responding tags. A reader also can lower noise influence by using correlator thresholds, since the scheme multiplexes IDs by CDMA-based communication. The effectiveness of the re-transmission was confirmed experimentally even in noisy channels, and the ID error rate derived from the emulation was 1.910-5. The emulation was useful for deriving an optimum set of RFID system parameters to be used in the design of mixed analog and digital integrated circuits for RFID communication.

We propose an ASK modulator and Antenna driver for multi-standard 13.56 MHz RFID readers and NFC devices. The proposed transmitters of RFID readers and NFC devices consist of ASK modulator, inverting output driving buffer and off-chip antenna with a matching circuit. The ASK modulation depth can easily be controlled by adjusting duty ratio by the delay line circuit. The test chip was fabricated by using a 0.35 µm double poly CMOS process. The measured results demonstrated that the proposed circuit has met the standard specifications.

Radio frequency identification (RFID) enables everyday objects to be identified, tracked, and recorded. The RFID tags are must be extremely simple and of low cost to be suitable for large scale application. An efficient RFID anti-collision mechanism must have low access latency and low power consumption. This paper investigates how to recognize multiple RFID tags within the reader's interrogation ranges without knowing the number of tags in advance by using framed ALOHA. To optimize power consumption and overall tag read time, a combinatory model was proposed to analyze both passive and active tags with consideration on capture effect over wireless fading channels. By using the model, the parameters on tag set estimation and frame size update were presented. Simulations were conducted to verify the analysis. In addition, we come up with a proposal to combat capture effect in deterministic anti-collision algorithms.

An ultra-small (0.4 0.4 mm2) radio frequency identification (RFID) chip named µ -chip has been developed for use in a wide range of individual recognition applications. The chip is designed to be 0.06 mm thick so that it can be applied to paper and to thin paper-like media, which have been used widely in retailing to create certificates that have monetary value, as well as to token-type devices. The µ-chip has been designed and fabricated using 0.18 µm standard CMOS technology with 3-layer aluminum metallization. The chip has a 128-bit memory. The memory data is easily read by applying a 2.45 GHz microwave radio frequency identification circuit technique. The minimum operating voltage of the chip's digital circuits is 0.5 V. This chip has attached to a thin-film external antenna. The chip terminals are connected to the antenna by an anisotropic conductive film (ACF). This type of structure results in a 0.15 mm thin transponder. The maximum communication distance between the µ -chip and a reader is 300 mm at a reader power of 300 mW.

This paper describes a CMOS transponder IC for RFID applications. A full-wave rectifier implemented using NMOS transistors supplies the transponder with a dc supply voltage. A 64-bit ROM has been designed for a data memory. Front-end impedance modulation and Manchester coding are used for transmitting the data from the transponder memory to the reader. A new damping circuit has been proposed and employed for impedance modulation. The designed circuit has been fabricated using a 0.65 µm 2-poly, 2-metal CMOS process. Measurement results show that it has a constant damping rate of around 20-25% and a data transmission rate of 3.9 kbps at a 125 kHz RF carrier. Die area is 0.9 mm0.4 mm. The measured reading distance is up to 7 cm.