• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1444-1451
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• 2009

This paper first proposes diverse C determining models in the Q algorithm which is proposed in the EPCglobal C1 Gen 2 standard and then compares and analyzes its performance. EPCglobal C1 Gen 2 standard proposes the slot-count (Q) selection algorithm for multiple tag identification environment, but there is no such definition for the C value which modifies the Q value depending on collision or no reply. During the tag anti-collision process, the Q algorithm adds C to the Q when there is a collision and reduces the Q by C when there is no reply. The modified Q value updates new slot-counts for tags which determines the tag identification speed, so the C value is an important factor. However, many researches only intend to increase the tag identification speed by proposing a new method or modifying the Q algorithm without any research about the C value. This paper suggests diverse C models which satisfies the EPCglobal C1 Gen 2 and analyzes their performance in the multi tag identification environment. The result of this paper can be used as an index for future researches on EPCglobal C1 Gen 2 C models and multiple tag identification performance.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.727-730
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• 2006

RFID 시스템은 유비쿼터스 컴퓨팅 환경에서 중요한 기술로 주목하고 있다. RFID의 국제 표준으로 자리 잡고 있는 EPCglobal Class-1 Gen-2 RFID 시스템을 통해서 전 세계 어디에서도 문제없이 인식될 것으로 보인다. 그러나 EPCglobal Class-1 Gen-2 RFID 시스템은 위협의 요소들을 가지고 있다. 본 논문에서는 표준에서 승인된 태그의 능력을 사용하여 표준의 수정을 최소화시켜 보안의 문제점을 해결 할 수 있는 방안을 제시한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1047-1056
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• 2007

In this paper, we analyze the performance of the encoding and the modulation processes in the downlink and uplink of the EPCglobal Gen-2 system through the analysis and simulation. Furthermore, the synchronization issues on time and frequency domain and the preamble architecture are evaluated. By incorporating the encoding and the modulation technigue in the downlink and uplink, we assess the performance of the EPCglobal Gen-2 system. We also introduce the encoding and backscatter modulation process as well as the BER performance of FM0 code. In addition, the importance and the role of the frequency and time synchronization, such as the preamble and frame synchronization are explained. Through the simulation in the uplink on the detection probability through preamble, we find that the detection probability approaches 1 for 13 dB $E_b/N_0$.

• Journal of information and communication convergence engineering
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• v.8 no.3
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• pp.307-311
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• 2010

EPCglobal Class-1 Gen-2 protocol has been proposed for UHF-band RFID systems. In Gen-2 standard, Q-algorithm was proposed to select a frame size for the next query round without estimating the number of tags. Therefore, the Q-algorithm has advantage that the reader's algorithm is simpler than other algorithms. However, it is impossible to allocate the optimized frame size. Also, the original Q-algorithm did not define an optimized parameter C for adjusting the frame size. In this paper, we propose an adaptive Q-algorithm with the different parameter $C_c$ and $C_i$ in accordance with the status of reply slot. Simulation results show that the proposed adaptive Q-algorithm outperforms the original Gen-2 Q-algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.752-760
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• 2010

This paper investigates the performance of EPCglobal Generation-2(Gen-2) radio frequency identification(RFID) protocol under reader-to-reader interfering environments. We establish a modified discrete-time Markov chain(DTMC) model for the Gen-2 and accordingly obtain quantitative results of query success rate(QSR) and tag identification speed (TIS). Extensive simulations validate our theoretical analysis and demonstrate that the number of tags over 100 has little impact on the performance. TIS linearly decreases by 10 tags/sec/reader as the number of interfering readers increases. Our model for Gen-2 protocol is also useful to study the performance of other RFID protocols.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.653-655
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• 2011

EPCglobal proposed a Q-algorithm, which is used for selecting a slot-count in the next query round. However, it is impossible to allocate an optimized slot-count because the original Q-algorithm did not define an optimized weight C value. In this paper, we propose an adaptive Q-algorithm, in which we differentiate the weight values with respect to collision and empty slots. The weight values are defined with the identification time as well as the collision probability.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1133-1138
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• 2010

In the anti-collision scheme proposed by EPCglobal Class-1 Gen-2 standard, the frame size for a query round is determined by Q-algorithm. In the Q-algorithm, the reader calculates a frame size without estimating the number of tags in it's identification range. It uses only the slot status. Therefore, Q-algorithm has advantage that the reader's algorithm is simpler than other algorithms. However, it cannot allocate an optimized frame size because it does not consider the number of tags. Also, the conventional Q-algorithm does not define an optimized parameter value C for adjusting the frame size. In this paper, we propose a modified Q-algorithm and evaluate the performance with computer simulations. The proposed Q-algorithm estimates the number of tags at every query round, and determines the parameter value C based on the estimated number of tags.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1013-1020
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• 2009

This paper proposes an authentication protocol using the key server in the ECPglobai RFID system. The proposed authentication protocol uses the key server and the time-out mechanism to resist various attacks including DoS(Denial of Service) attack. For easy implementation, the proposed protocol also uses the function existing in EPCglobal class 1 gen2 protocol without additive function such as hash function. The proposed protocol is evaluated through two analytical methods. The correctness of the proposed protocol is proved using the GNY analysis. By the security analysis, this paper showed that the proposed protocol is resistant to various attacks including DoS attack. The analytical results demonstrated that the proposed protocol offered a secure RFID system.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06d
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• pp.172-176
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• 2007

유통분야에서 물품관리를 위해 사용되었던 바코드를 대체할 차세대 인식기술로 꼽히는 RFID 기술은 IT기술의 주요 시장으로 부상하면서 다양한 연구가 이루어지고 있는 분야이다. 유통 및 물류분야에서는 다량의 물품을 실시간으로 식별해야 하는 경우가 필요한데 이를 위해 여러 개의 리더가 동시에 사용 된다. RFID 시스템을 구축하는데 있어서 다중 리더 운영 기법은 전체 RFID 시스템의 성능을 좌우한다. EPCglobal에서 제안 된 Gen2 프로토콜은 900MHz 대역의 단일 통합 표준으로서 ISO/IEC 18000-6 C타입으로 채택되었다. 하지만 Gen2 프로토콜에서 다중 리더 운영 정책에 대해서 Session 기능을 간단히 내놓았을 뿐 자세한 소프트웨어 응용법을 제시하지 않았으며, 이에 관한 미들웨어 연구도 이루어지고 있지 않다. 본 논문에서는 현재 Gen2 프로토콜에서의 태그 인식 기술과 EPCglobal에서 제안하는 RFID 프로토콜, Sesssion 개념을 소개하고 Gen2 프로토콜을 이용하는 RFID 시스템에 다중 리더 관리 모듈을 설계를 통해 다중 리더를 운영하는 기법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.470-475
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• 2012

In Q-algorithm of EPCglobal Class-1 Gen-2 RFID system, the initial value of $Q_{fp}$, which is the slot-count parameter, is not defined in the standard. And the values of weight C, which is the parameter for incrementing or decrementing the slot-count size, are not determined. Therefore, if the number of tags is small and we let the initial $Q_{fp}$ be large, the number of empty slot will be large. On the other hand, if we let the initial $Q_{fp}$ be small in spite of many tags, almost all the slots will be collided. Also, if the reader selects an inappropriate weight, there are a lot of empty or collided slots. As a result, the performance will be declined because the frame size does not converge to the optimal point quickly during the query round. In this paper, we propose a scheme to allocate the optimal initial $Q_{fp}$ through the tag number estimation and select the weight based on the slot-count size of current query round.