• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.2 s.344
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• pp.27-38
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• 2006

When an RFID reader attempts to read tags, interference might occur if the neighboring readers also attempt to communicate with the same tag at the same time or the neighboring readers use the same frequency at the same time. These interferences cause the RFID reader collision. When the RFID reader collision occirs, either the command from the reader can not be transmitted to the tags or the response from the tags can not be received by the reader correctly. RFID reader anti-collision algorithms have been developed to reduce it. One of the best blown reader anti-collision algorithms is the Colorwave algorithm proposed by MIT. The Colorwave algorithm reduces the reader collisions by having the readers operate at different times. In Colorwave the time is divided into frames and a frame is divided into a number of slots. Each reader can access the tags using the slot time assigned to it. Depending on the probability of the interference, the colorwave adjusts the frame size to improve the efficiency. In this paper, we analyze the operations and the performance of the Colorwave algorithm and identify the problems of the algorithm. We also show that by adding some modifications to the algorithm the performance can be improved significantly.

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.255-261
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• 2008

RFID(Radio Frequency IDentification) is a technology that automatically identifies objects containing the electronic tags by using radio frequency. In RFID system, the reader needs the anti collision algorithm for fast identifring all of the tags in the interrogation zone. This Paper proposes the tree based TPAE(Tag Prediction Algorithm using Extra bit) algorithm to arbitrate the tag collision. The proposed algorithm can identify tags without identifring all the bits in the tag ID. The reader uses the extra bit which is added to the tag ID and if there are two collided bits or multiple collided bits, it checks the extra bit and grasps the tag IDs concurrently. In the experiment, the proposed algorithm had about 50% less query iterations than query tree algorithm and binary search algorithm regardless of the number of tags and tag ID lengths.

• Journal of Internet Computing and Services
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• v.14 no.4
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• pp.25-33
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• 2013

The procedure of the arbitration which is the tag collision is essential because the multiple tags response simultaneously in the same frequency to the request of the Reader. This procedure is known as Anti-collision and it is a key technology in the RFID system. In this paper, we propose the 4-Bit Pattern Slot Allocation(4-BPSA) algorithm for the high-speed identification of the multiple tags. The proposed algorithm is based on the tree algorithm using the time slot and identify the tag quickly and efficiently through accurate prediction using the a slot as a 4-bit pattern according to the slot allocation scheme. Through mathematical performance analysis, We proved that the 4-BPSA is an O(n) algorithm by analyzing the worst-case time complexity and the performance of the 4-BPSA is improved compared to existing algorithms. In addition, we verified that the 4-BPSA is performed the average 0.7 times the query per the Tag through MATLAB simulation experiments with performance evaluation of the algorithm and the 4-BPSA ensure stable performance regardless of the number of the tags.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.287-292
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• 2007

In this paper, a QT_ecfi algorithm is proposed for identifying all the tags within the identification range. The proposed QT_ecfi algorithm revises the QT algorithm, which has a memoryless property. In the QT_ecfi algorithm, the tag will send the remaining bits of their identification codes when the query string matches the first bits of their identification codes. When the reader receives all the responses of the tags, it knows which bit is collided. If the collision occurs in the last bit, the reader can identify two tags simultaneously without further query. While the tags are sending their identification codes, if the reader detects a collision bit, it will send a signal to the tags to stop sending. According to the simulation results, the QT_ecfi algorithm outperforms the QT algorithm in terms of the number of queries and the number of response bits.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.98-98
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• 2004

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.91-93
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• 2006

RFID(Radio Frequency IDentification) 기술은 RF 신호를 사용하여 물품에 부착된 전자 태그(tag)를 식별하는 비접촉자동인식 기술이다. 이런 RFID 기술의 확산을 위해서는 리더가 다수의 태그를 빠른 시간 안에 인식하는 다중 태그 식별 문제를 해결 해야만 한다. 지금까지 이 문제를 해결하기 위한 충돌 방지(anti-collision) 알고리즘이 많이 개발되었다. 본 논문에서는 이런 충돌 방지 알고리즘 중에서 18000-6 Type A, Type B와 Type C로 새롭게 채택된 EPCglobal Class1 Generation2, 그리고 Query Tree Protocol에 대한 시뮬레이션 시스템의 구조를 소개하고 실제 시뮬레이션 했을 때의 각 알고리즘에 대한 간단한 성능 평가를 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2541-2546
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• 2009

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, the Q-algorithm has advantage that the reader's algorithm is simpler than other DFSA algorithms. However, the standard does not define an optimized parameter value for adjusting the frame size. In this paper, we propose the optimized parameter values for minimizing the identification time by various computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.448-454
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• 2007

This paper proposes an estimation method of number of tags which may be necessary in improving anti-collision performance for ALOHA-based RFID systems. In ALOHA-based anti-collision algorithms, since the performance of the multi tag identification can be improved by allocating the optimal slot size corresponding to the number of tags, it is needed to exactly estimate the number of tags. The proposed method uses the a priori knowledge of the relation between the expectation of the number of empty slots and the number of tags. After measuring the number of empty slots in one ROUND, we estimate the number of tags which corresponds to the expectation of the number of empty slots nearest to the measured one. Simulation results show that the proposed method is superior to conventional methods in terms of the estimation accuracy and the computational complexity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2569-2574
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• 2013

In 13.56MHz RFID system of Auto-ID center, STAC protocol is defined as an anti-collision algorithm for multiple tag reading. In STAC protocol, the reader uses the tag number estimation scheme to determine the number of slots for the next reply round. If errors occur in the estimated number of tags, the identification performances will be degraded due to a lot of collision or idle slots. Therefore, in this paper, we propose an ERPB algorithm that the reader cancels the reply round when it experiences a series of collision or idle slots during the current round. The transmission probability control for the tag is also applied to the proposed algorithm. Through simulations, it is demonstrated that the collision rate for the proposed scheme is about 39% lower than STAC protocol. Therefore, the proposed scheme can achieve faster tag identification time compared with STAC protocol due to the low collision rate.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.33-41
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• 2008

As RFID technology is developing and increasingly being used in many applications, the implementation is changing from single reader to multiple readers even dense readers. Since the number of readers is increasing, there are more collisions between readers and much interference between readers and tags. Therefore, to avoid interference or collision, many algorithms have being proposed, such as Gen2 dense mode, LBT(listen before talk), TDMA based method. In this paper, we propose a null frame algorithm, which calculates the collision probability in frame slotted aloha scheme and use this information to avoid the possible collisions. Comparing with conventional scheme, our proposed algorithm has some advantages in terms of reader collision number and required frame numbers.