• The KIPS Transactions:PartA
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• v.15A no.5
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• pp.287-294
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• 2008

A tag collision arbitration algorithm for RFID passive tags is one of the important issues for fast tag identification, since reader and tag have a shared wireless channel in RFID system. This paper suggests Hyper-Hybrid Query Tree algorithm to prevent the tag-collisions. The suggested algorithms determine the specified point in time for tag to transfer ID to reader by using value 1 of the upper 3 bit based on Query Tree. Also, because the transferred upper 3 bits of tag is different depending on the time of transfer, it is possible to predict in the suggested Algorithm. In the performance evaluation through simulation, it shows the suggested algorithm has higher performance in the number of queries compared to other Tree-based protocols.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.802-805
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• 2008

RFID 시스템에서 리더와 태그는 단일 무선 공유 채널을 갖기 때문에 RFID 수동형 태그를 위한 태그 충돌 중재가 태그 인식을 위한 중요한 이슈이다. 본 논문에서는 태그 충돌 방지를 위한 Improved Hybrid Query Tree algorithm 을 제안한다. 제안된 알고리즘은 쿼리 트리를 기반으로 태그가 리더에게 ID 를 전송하는 시점을 전송 ID 상위 3 비트 내의 '1' 값을 이용하여 결정한다. 또한 전송받은 Tag 의 상위 3 비트는 충돌이 발생하더라도 전송 슬롯에 따라 다르므로 제안한 알고리즘에서 예측이 가능하다. 시뮬레이션을 통한 성능 평가에서 다른 트리 기반 프로토콜에 비해 제안한 알고리즘이 쿼리 횟수에서 높은 성능을 갖는다는 것을 보여준다.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.3
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• pp.1-9
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• 2010

In recent year, the cores of ubiquitous environment are sensor networks and RFID systems. RFID system transmits the electronic information of the tag to the reader by using RF signal. Collision happens in RFID system when there are many matched tags, and it degrades the tag identification performance. Such a system needs algorithm which is able to arbitrate tag collision. This paper suggests a hybrid method which reduces collision between the tags, and can quickly identify the tag. The proposed method operates based on certainty, which takes an advantage of tree based algorithm, and to reduce collision it selects transmission time slot by using tag ID. The simulation results show the suggested method has higher performance in the number of queries and collision compared to other tree based and hybrid algorithms.

• Journal of the Korea Society of Computer and Information
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• v.19 no.12
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• pp.111-121
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• 2014

In this paper, we propose tree-based hybrid query tree architecture utilizing time slot. 4-Bit Pattern Slot Allocation(4-SL) has a 8-ary tree structure and when tag ID responses according to query of the reader, it applies a digital coding method, the Manchester code, in order to extract the location and the number of collided bits. Also, this algorithm can recognize multiple Tags by single query using 4 fixed time slots. The architecture allows the reader to identify 8 tags at the same time by responding 4 time slots utilizing the first bit($[prefix+1]^{th}$, F ${\in}$ {'0' or '1'}) and bit pattern from second ~ third bits($[prefix+2]^{th}{\sim}[prefix+3]^{th}$, $B_2{\in}$ {"00" or "11"}, $B_1{\in}$ {"01" or "10"}) in tag ID. we analyze worst case of the number of query nodes(prefix) in algorithm to extract delay time for recognizing multiple tags. The identification delay time of the proposed algorithm was based on the number of query-responses and query bits, and was calculated by each algorithm.

• Journal of Internet Computing and Services
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• v.14 no.5
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• pp.1-10
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• 2013

RFID(Radio Frequency Identification) system is non-contact identification technology. A basic RFID system consists of a reader, and a set of tags. RFID tags can be divided into active and passive tags. Active tags with power source allows their own operation execution and passive tags are small and low-cost. So passive tags are more suitable for distribution industry than active tags. A reader processes the information receiving from tags. RFID system achieves a fast identification of multiple tags using radio frequency. RFID systems has been applied into a variety of fields such as distribution, logistics, transportation, inventory management, access control, finance and etc. To encourage the introduction of RFID systems, several problems (price, size, power consumption, security) should be resolved. In this paper, we proposed an algorithm to significantly alleviate the collision problem caused by simultaneous responses of multiple tags. In the RFID systems, in anti-collision schemes, there are three methods: probabilistic, deterministic, and hybrid. In this paper, we introduce ALOHA-based protocol as a probabilistic method, and Tree-based protocol as a deterministic one. In Aloha-based protocols, time is divided into multiple slots. Tags randomly select their own IDs and transmit it. But Aloha-based protocol cannot guarantee that all tags are identified because they are probabilistic methods. In contrast, Tree-based protocols guarantee that a reader identifies all tags within the transmission range of the reader. In Tree-based protocols, a reader sends a query, and tags respond it with their own IDs. When a reader sends a query and two or more tags respond, a collision occurs. Then the reader makes and sends a new query. Frequent collisions make the identification performance degrade. Therefore, to identify tags quickly, it is necessary to reduce collisions efficiently. Each RFID tag has an ID of 96bit EPC(Electronic Product Code). The tags in a company or manufacturer have similar tag IDs with the same prefix. Unnecessary collisions occur while identifying multiple tags using Query Tree protocol. It results in growth of query-responses and idle time, which the identification time significantly increases. To solve this problem, Collision Tree protocol and M-ary Query Tree protocol have been proposed. However, in Collision Tree protocol and Query Tree protocol, only one bit is identified during one query-response. And, when similar tag IDs exist, M-ary Query Tree Protocol generates unnecessary query-responses. In this paper, we propose Adaptive M-ary Query Tree protocol that improves the identification performance using m-bit recognition, collision information of tag IDs, and prediction technique. We compare our proposed scheme with other Tree-based protocols under the same conditions. We show that our proposed scheme outperforms others in terms of identification time and identification efficiency.

• Journal of KIISE:Software and Applications
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• v.36 no.7
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• pp.560-570
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• 2009

RFID, Radio Frequency Identification, is a technology of automated identification replacing bar-code. RFID technology has advantages that it recognizes fast and it is strong to contamination using wireless communication. However, there are difficult problems that should be solved for popularization of RFID. Among of these, tag anti-collision problem is dealed in this paper. It affected the performance of RFID system directly. This paper analyzes conventional algorithms and proposes new algorithms of tag anti-collision. The algorithm proposed was composed of appropriate properties to each phase of distribution and recognition as hybrid between ALOHA-based algorithm and QT-based algorithm. At phase of distribution, the number of tags recognizing at a frame was reduced using ALOHA-based algorithm. It addressed the delay problem because of deep depth of tree. At phase of recognition, it solved ALOHA-based chronic problem that couldn't recognize all the tags sometimes. Moreover, QTR algorithm that recognize by reversed tag IDs was adopted for the performance. The FQTR algorithm proposed in this paper showed brilliant performance as compared with convention algorithms by simulation.