• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.483-492
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• 2007

In this paper, we propose a new hybrid approach based on query tree protocol to arbitrate tag collisions in RFID systems. The hybrid query tree protocol that combines a tree based query protocol with a slotted backoff mechanism. The proposed protocol decreases the average identification delay by reducing collisions and idle time. To reduce collisions, we use a 4-ary query tree instead of a binary query tree. To reduce idle time, we introduce a slotted backoff mechanism to reduce the number of unnecessary Query commands. Simulation and numerical analysis reveal that the proposed protocol achieves lower identification delay than existing tag collision arbitration protocols.

• 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 the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.99-108
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• 2010

RFID(Radio Frequency IDentification) is a technology that automatically identifies objects containing the electronic tags by using radio wave. When there are some tags in the domain of the RFID reader, the mechanism that can solve a collision between the tags occurs is necessary. The multi tag identification problem is the core issue in the RFID and could be resolved by the anti-collision algorithm. However, RFID system has another problem. The problem id user information security. Tag response easily by query of reader, so the system happened user privacy violent problem by tag information exposure. In the case, RFID system id weak from sniffing by outside. In this paper, We study of security robustness for tree-walking algorithm, query tree algorithm and advanced query tree algorithm of tree based memoryless algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.16-18
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• 2006

RFID는 RF신호를 이용하여 물체에 부착된 태그(tag)를 읽어 물체를 식별하는 비 접촉 인식 기술이다. RFID 리더의 식별영역에 여러 개의 태그가 있는 경우 이들 사이의 충돌(collision)이 발생되기 때문에 이들을 식별할 수 있는 메커니즘이 있어야 한다. 본 논문에서는 먼저 기존에 제안된 트리 기반 메모래스 충돌방지 알고리즘들을 살펴보고, 본 논문에서 제안하는 향상된 쿼리 기반 충돌 알고리즘(AQT : Advanced Query Tree based Collision Algorithm)을 소개한다.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.6
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• pp.435-445
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• 2013

One of the most challenging issues in radio frequency identification (RFID) and near field communications (NFC) is to correctly and quickly recognize a number of tag IDs in the reader's field. Unlike the probabilistic anti-collision schemes, a query tree based protocol guarantees to identify all the tags, where the distribution of tag IDs is assumed to be uniform. However, in real implements, the prefix of tag ID is uniquely assigned by the EPCglobal and the remaining part is sequentially given by a company or manufacturer. In this paper, we propose an enhanced M-ary query tree protocol (EMQT), which effectively reduces unnecessary query-response cycles between similar tag IDs using m-bit arbitration and tag expectation. The theoretical analysis and simulation results show that the EMQT significantly outperforms other schemes in terms of identification time, identification efficiency and communications overhead.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.382-388
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• 2011

This paper proposes a mechanism that guarantees secured performance against DDoS attack to protect data from free-roaming agent. Also, as it makes up QCRT(query chain relationship tree) structure which is an enhanced chain relation of existing chain relations that improves extension, It also finds malicious elements. The proposed mechanism extends chain relationship of agent as well by checking chain relation structure as a structure according to the route of agent. For it complements existing weakness with single-side chain relation extension, it guarantees secure performance against DDoS and truncation attacks from mobile agent.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1151-1156
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• 2017

It is common to achieve lower performance in traversing tree data structures in GPU than one expects. In this paper, we analyze the reason of lower-than-expected performance in GPU tree traversal and present that the warp divergences is caused by the branch instructions ("if${\ldots}$ else") which appear commonly in tree traversal CUDA codes. Also, we compare the parallel shifted sort algorithm which can reduce the number of warp divergences with a kd-tree CUDA implementation to show that the shifted sort algorithm can work faster than the kd-tree CUDA implementation thanks to less warp divergences. As the analysis result, the shifted sort algorithm worked about 16-fold faster than the kd-tree CUDA implementation for $2^{23}$ query points and $2^{23}$ data points in $R^3$ space. The performance gaps tend to increase in proportion to the number of query points and data points.

• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.316-327
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• 2007

RFID (Radio Frequency Identification) is one of the most promising air interface technologies in the future for object identification using radio wave. If there are multiple tags within the range of the RFID tag reader, all tags send their tag identifications to the reader at the same time in response to the reader's query. This causes collisions on the reader and no tag is identified. A multi-tag identification problem is a core issue in the RFID. It can be solved by anti-collision algorithm such as slot based ALHOA algorithms and tree based algorithms. This paper, proposes a collision tree based anti-collision algorithm using collision tree in RFID system. It is a memory-less algorithm and is an efficient RFID anti-collision mechanism. The collision tree is a mechanism that can solve multi-tag identification problem. It is created in the process of querying and responding between the reader and tags. If the reader broadcasts K bits of prefix to multiple tags, all tags with the identifications matching the prefix transmit the reader the identifications consisted of k+1 bit to last. According to the simulation result, a proposed collision tree based anti-collision algorithm shows a better performance compared to tree working algorithm and query tree algorithm.