• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.203-206
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• 2005

Recently, the RFID(Radio Frequency Identification) technology has gained significant attention. One of the performance issues in RFID systems is to resolve the tag collision among responses from RFID tags. In this paper, we proposed a new scheme for estimation of the number of tags in the reader filed. The scheme is used by anti-collision algorithm to identify multiple tags efficiently. And we also present the simulation result that shows the proposed scheme to estimate tags efficiently and also to improve the systems efficiency.

• 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 Korea Multimedia Society
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• v.15 no.11
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• pp.1358-1368
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• 2012

A tag sequence estimation scheme is to estimate the physical sequence of passive RFID tags that are linearly spread using the movement of a RFID reader. Since RFID readers communicate with the passive tags by very weak radio waves, scanning passive tags are unstable. In this paper, we applied round-trip scanning of a reader to enhance the tag sequence estimation. Proposed scheme first determines the turning point of the reader movement, and then estimates the sequence of the tags using the tag sets scanned in each read cycles. Test experiments show that the proposed scheme can improve the estimation accuracy.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.164-169
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• 2009

An RFID system consists of radio frequency tags attached to objects that need to be identified and one or more electromagnetic readers. Unlike the traditional bar code system, the great benefit of RFID technology is that it allows information to be read without requiring contact between the tag and the reader. For this contact-less feature, RFID technology in the near future will become an attractive alternative to bar code in many application fields. In almost all the 13.56MHz RFID systems, FSA (Framed Slot ALOHA) algorithm is used for identifying multiple tags in the reader's identification range. In FSA algorithm, the tag identification time and system efficiency depend mainly on the number of tags and frame size. In this paper, we propose a tag number estimation scheme and a dynamic frame size allocation scheme based on the estimated number of tags.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2643-2648
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• 2012

In the RFID Sytem, When leaders recognize the tag, a anti-collision scheme is an important factor in the performance of the system. Probabilistic-based anti-collision scheme using the slot status is a technique to estimate the number of tags. the schemes to quickly and accurately estimate the number of tags has been a lot of research. However, A initial number tag are not considering in the number of tags unknown environment. In the paper, estimation scheme for the initial number of tag is proposed to solve the problems. we analyze the performance by the initial number of tag and the proposed scheme.

• Korean Management Science Review
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• v.29 no.3
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• pp.1-11
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• 2012

This paper considers a localization problem in time difference of arrival (TDOA)-based radio frequency identification (RFID) systems. To estimate the position of a target tag, this paper suggests three localization algorithms that use benchmark tags. The benchmark tags are the same type as the target tag, but either the locations or distance of the benchmark tags are known. Two algorithms use the benchmarks for auxiliary information to improve the estimation accuracy of the other localization algorithms such as least squared estimator (LSE). The other one utilizes the benchmarks as essential tags to estimate the location. Numerical tests show that the localization accuracy can be improved by using benchmark tags especially when an algorithm using the LSE is applied to the localization problem. Furthermore, this paper shows that our benchmark algorithm is valuable when the measurement noise is large.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.126-132
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• 2014

In this paper, a DFSA (Dynamic Framed Slotted ALOHA) based anti-collision algorithm is described and a performance improved algorithm of DFSA and FSA is proposed. The proposed method makes use of expected values and has merits in operation speed by estimating closest value of the number of tags on a single operation. The algorithm compares and analyses number of empty slots and collide slots in accordance with the number of tags, which enables estimation of actual number of tags. we simulated the proposed algorithm and compared it with conventional methods. Results show that our method needs average 18.8 rounds to identify all tags. In case of less than 1000 tags, an average of 18.2 rounds is necessary and an average of 19.2 rounds is needed to identify all tags for more than 1000 tags. The proposed algorithm improves processing speed by 3.1 % comparing to DFSA with cancellation strategy, 10.1 % comparing to DFSA, 37.5 % comparing to FSA(Framed Slotted ALOHA).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.469-474
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• 2009

An RFID system consists of radio frequency tags attached to objects that need to be identified and one or more electromagnetic readers. Unlike the traditional bar code system, the great benefit of RFID technology is that it allows information to be read without requiring contact between the tag and the reader. For this contact-less feature, RFID technology in the near future will become an attractive alternative to bar code in many application fields. In almost all the 13.56MHz RFID systems, FSA algorithm is used for identifying multiple tags in the reader's identification range. In FSA algorithm, the tag identification time and system efficiency depend mainly on the number of tags and frame size. In this paper, we propose a tag number estimation scheme and a dynamic frame size allocation scheme based on the estimated number of tags.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.814-821
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• 2005

When there are many tags using the same frequency around the reader in RFID system, they disturb each other and in the end their response cannot be received by the reader. To solve this disturbance and fast identify the tags, the anti-collision algorithm, which is the core technology in RFID system, is needed. We propose two ALOHA-type Dynamic Framed Slotted ALOHA(DFS-ALOHA) algorithms using Dynamic Slot Allocation(DSA), which dynamically allocates the frame size in accordance with the number of tags and Tag Estimation Method(TEM), which estimates the number of tags around the reader. We also compare the performance of the proposed DFS-ALOHA algorithms with that of the conventional Framed Slotted ALOHA (FS-ALOHA) algorithms and the algorithms proposed by Vogt using OPNET simulation. According to the analysis, the two proposed DFS-ALOHA algorithms(DFS-ALOHA I and DFS-ALOHA II) show better performance than the conventional ALOHA-based algorithms regardless of the number of tags. Although the two proposed DFS-ALOHA algorithms show the similar performance, BFS-ALOHA ll is better because it is easier to be implemented in the system and the complexity is lower.

• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.33-39
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• 2012

In this paper, we compare the accuracy of most representative radio frequency identification (RFID) tag estimation functions in the context of minimizing RFID tag identification delay. Before the comparisons, we first evaluate the accuracy of Schoute's estimation function, which has been widely adopted in many RFID tag identification processes, and show that its accuracy actually depends on the number of tags to be identified and frame size L used for dynamic frame slotted Aloha cycles. Through computer simulations, we show how the accuracy of estimation functions is related to the actual tag read performance in terms of identification delay.