• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8A
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• pp.794-804
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• 2008

In this paper, we analyze the performance of probabilistic slotted anti-collision algorithm used in EPCglobal Class-1 Generation-2 (Gen2). To increase throughput and system efficiency, and to decrease tag identification time and collision ratio, we propose new tag anti-collision algorithms, which are FAFQ (fired adjustable flamed Q) algorithm and AAFQ (adaptive adjustable framed Q) algorithm, by using QueryAdjust command. We also propose grouping method based on Gen2 to improve the efficiency of tag identification. The simulation results show that all the proposed algorithms outperform Q algorithm, and AAFQ algorithm performs the best. That is, AAFQ has an increment of 5% of system efficiency and a decrement of 4.5% of collision ratio. For FAFQ and AAFQ algorithm, the performance of grouping method is similar to that of ungrouping method. However, for Q algorithm in Gen2, grouping method can increase throughput and system efficiency, and decrease tag identification time and collision ratio compared with ungrouping method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.430-436
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• 2006

In this paper, a QT_rev protocol is proposed for identifying all the tags within the identification range. The proposed QT_rev protocol revises the QT protocol, which has a memoryless property. In the QT_rev protocol, the tag will send the remaining bits of their identification codes when the query string matches the first bits of their identification codes. After 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. According to the simulation results, the QT_rev protocol outperforms the QT protocol in terms of the number of queries and the number of response bits.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.561-571
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• 2006

RFID technology, as one contact-less identification technology with using electronic tag, is the field where its multiple researches have been studied. Especially, in the field of supply chain management, when it is necessary to identify a lot of objects by real-time, performance of anti-collision algorithm for multiple tag identification has an effect on performance of entire system. GEN2 is global, open, interoperability protocol for UHF RFID system, the active researches and developments are processed about it. In this paper, we introduce an anti-collision algorithm based on Slotted-ALOHA for GEN2 protocol, focus on estimating number of tags and setting number of slots and review the previous works. We propose new scheme that can estimate number of tags efficiently, and define system efficiency newly when it's used in setting number of slots. We also present result of compare and analysis with previous scheme through simulation. The proposed scheme of estimating number of tags is easy to implement, number of tags which is less than 4 times of number of slots can estimate tags efficiently, we also proved that identification efficiency based on weighted-slot distinguished with definition of previous slot efficiency can improve system efficiency.

• Journal of Internet Computing and Services
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• v.10 no.2
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• pp.133-141
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• 2009

A tag collision problem occurs when many tags are placed in a interrogation zone in RFID system. A tag collision problem is one of core issues and various protocols have been proposed to solve the collision problems. Generally tree-based protocols generate unique prefixes and identify tags with them as quick as possible. In this paper, we propose the QT-BCS protocol which decreases the identification time by reducing the number of query-response. The QT-BCS protocol makes a prefixes using time slot and bit change sensing unit. This protocol compares the current bit of tags until the current bit is differ from the previous one. When this occurs, all of the bits scanned so far are transferred to slot-0 and slot-1 depending on the first bit value in Reader. Consequently, this method can reduce the number of queries by tracing prefixes easily. Simulation result shows QT-BCS is more efficient in identifying tags than Query Tree and 4-ary Query Tree protocol.

• 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.

• 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.

• 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 the Institute of Electronics Engineers of Korea CI
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• v.44 no.6
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• pp.51-61
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• 2007

In this paper, Air-interface protocols of ISO 18000-6 Types and EPCglobal Classes applied to RFID system in UHF band are analyzed, and those anticollision algorithms are realized. Also, the each algorithm which improves the performance of standard protocol is proposed, and the performance is compared when clock period of link timing is a identical condition on $12.5{\mu}s$. As the result, when 500 tags exist simultaneously inside reader interrogation zone, the tag recognition performance of a standard protocol is better in preceding order of Class-1 Generation-1, Type B, Type A, Class-0 and Class-1 Generation-2. And also the performance of improved protocol is better in ascending order of Type B, Type A, Class-1 Generation-1, Class-0 and Class-1 Generation-2. Therefore, performance of tag recognition remarkably depends on the regulated clock period in the protocol and link timing between a reader and a tag.

• 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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.712-714
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• 2016

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 13.56MHz RFID system of Auto-ID center, STAC protocol is defined as an anti-collision algorithm for multiple tag reading. In this paper, we propose a STAC/PS algorithm that the PS algorithm is applied in the STAC protocol. The simulation results show that the STAC/PS algorithm can achieve faster tag identification speed compared with STAC protocol due to the low collision rate.