• ETRI Journal
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• v.30 no.5
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• pp.653-662
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• 2008

Arbitration of tag collision is a significant issue for fast tag identification in RFID systems. A good tag anti-collision algorithm can reduce collisions and increase the efficiency of tag identification. EPCglobal Generation-2 (Gen2) for passive RFID systems uses probabilistic slotted ALOHA with a Q algorithm, which is a kind of dynamic framed slotted ALOHA (DFSA), as the tag anti-collision algorithm. In this paper, we analyze the performance of the Q algorithm used in Gen2, and analyze the methods for estimating the number of slots and tags for DFSA. To increase the efficiency of tag identification, we propose new tag anti-collision algorithms, namely, Chebyshev's inequality, fixed adjustable framed Q, adaptive adjustable framed Q, and hybrid Q. The simulation results show that all the proposed algorithms outperform the conventional Q algorithm used in Gen2. Of all the proposed algorithms, AAFQ provides the best performance in terms of identification time and collision ratio and maximizes throughput and system efficiency. However, there is a tradeoff of complexity and performance between the CHI and AAFQ algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1C
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• pp.59-66
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• 2007

This paper proposes a windowing method to reduce noise effect and bit synchronization error caused by tolerance of a tag-response signal for ISO/IEC 18000-6 type-B readers. A tag response signal has very weak power because of a back-scattering modulation scheme and thus may be sensitive to noise. In addition, bit tolerance admitted in a tag response signal requires robust timing synchronization because it affects readers' detection performance. To reduce the two undesirable effects in a tag signal, we acquire bit transition position by using variable windows from over-sampled data, and average whole data in one bit duration. With a hardware system adopting the proposed method, we tested and verified its performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3660-3669
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• 2011

Demands for systemized management of workers' safety systemically in construction sites have been increased. Industrial accidents at work places are often happened by risk factors of construction sites, and also it brings a lot of loss as the correct direction for workers about locations to work is not delivered properly. In this paper, a safety supervision system for construction sites is designed and implemented to figure out the location of workers accurately and to provide the information about the status of works and workers in real-time by personal device which is based on RFID. The system designed in this paper achieved high performance in its function and efficiency through a performance test, compared with existing analogous systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.12
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• pp.2763-2768
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• 2013

In this paper, a design method for a compact slot antenna for 5.8 GHz RFID band (5.725-5.875 GHz) is studied. The proposed slot antenna is size-reduced by bending both ends of the straight slot in "I"-shape, and a rectangular feed patch is located inside the slot. The effects of slot length, location of feed patch, and width and length of feed patch on the antenna performance are examined. A prototype antenna with optimized parameters for 5.8 GHz band is fabricated on an FR4 substrate and tested experimentally to verify the results of this study. The experimental results show that the frequency band for a VSWR < 3 ranges 5.72-6.13 GHz (bandwidth 410 MHz), and it corresponds fairly well with the simulated band 5.64-5.97 GHz (bandwidth 330 MHz). The fabricated antenna shows good radiation performance such as maximum power density in both directions normal to the slot plane, low cross-polarization level of < -20 dB, and realized gain > 0 dBi within the frequency band.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.3
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• pp.195-198
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• 2013

Many libraries utilize RFID tags for checking in and out of books. However, the recognition rate of this automatic process may depend on the orientation of antennas and RFID tags. Therefore we need supplemental systems to improve the recognition rate. The proposed algorithm sets up the ROI of the book existing area from the input image and then performs Canny edge detection algorithm to extract edges of books. Finally Hough line transform algorithm allows to detect the number of books from the extracted edges. To evaluate the performance of the proposed method, we applied our method to 350 book images under various circumstances. We then analyzed the performance of proposed method from results using recognition and mismatch ratio. The experimental result gave us 97.1% accuracy in book counting.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.797-802
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• 2005

In this paper, we design a UHF band RFID tag antenna which is conjugate matched to an impedance of a chip and also mountable on conductive materials. The proposed tag antenna is very compact($50{\times}30{\times}4mm$) with a modified PIFA shape. The proposed tag antenna has an advantage of easy matching to various chip input impedances. The performance of the antenna is evaluated by monitoring RCS in the reader direction. The RCS of the designed tag is $-10.2\;dBm^2$ when the chip is shorted and is $-21\;dBm^2$ when the chip impedance is a complex conjugate of the antenna impedance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.807-812
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• 2015

In RFID system, when multiple tags respond simultaneously, a collision can occur. A method that solves this collision is referred as anti-collision algorithm. In 13.56MHz RFID system of Auto-ID center, STAC protocol is defined as an anti-collision algorithm for multiple tag reading. The PS algorithm divides the tags within the identification range of reader into smaller groups by increasing the transmission power incrementally and identifies them. In this paper, we propose a STAC/PS algorithm that the PS algorithm is applied in the STAC protocol. Through simulations, it is demonstrated that the collision rate for the proposed algorithm is about 50% lower than STAC protocol. Therefore, the STAC/PS algorithm can achieve faster tag identification speed compared with STAC protocol due to the low collision rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.184-194
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• 2005

One of the most important factors that decide the overall performance of RFID system is anti-collision algorithm. By enhancing the anti-collision algorithm, we can increase the number of RFID tags that can be processed in unit time. Two anti-collision algorithms are most widely prevailed: one is ALOHA-based protocol and the other is a binary tree walking method, but these are still under research. In this paper, we suggest an anti-collision algorithm named AAC(Address Allocating and Calling) using pre-distributed random address, which is much faster and more efficient than existing ones. Finally, we evaluate our scheme using mathematical analysis and computer simulation.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.65-71
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• 2011

In this paper, the RFID / USN-based ad-hoc network structure is presented for efficient operation of a container terminal yard. Communication between fixed or mobile devices in the container terminal yard is accomplished through the ad-hoc node, to collect the status information of a container in real time. Any outside shipper of the container as well as central server allows to share the status information of a container through ad-hoc communication. In addition, to predict the maximum wireless transmission range of nodes by RFID tag position in the yard, LAODV (Location based AODV) routing protocol is proposed. The validity is proved by performance evaluation via computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.806-811
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• 2006

In RFID system, when multiple tags respond simultaneously, a collision can occur. A method that solves this collision is referred to as anti-collision algorithm. Among the existing anti-collision algorithms, SFSA, though simple, has a disadvantage that when the number of tags is variable, the system performance degrades because of the fixed frame size. This paper proposes a new anti-collision algorithm called DFSA which determines the optimal frame size using the number of collided slots at every frame. According to the simulation results, the tag identification time of the proposed algorithm is faster than that of SFSA.