• 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.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.267-274
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• 2009

For the implementation of a RFID system, an anti-collision algorithm is required to identify multiple tags within the range of a RFID Reader. There are two methods of anti-collision algorithms for the identification of multiple tags, conclusive algorithms based on tree and stochastic algorithms based on slotted ALOHA. In this paper, we propose a Dynamic Framed Slotted ALOHA-Slot Congestion(DFSA-SC) Algorithm. The proposed algorithm improves the efficiency of collision resolution. The performance of the proposed DFSA-SC algorithm is showed by simulation. The identification time of the proposed algorithm is shorter than that of the existing DFSA algorithm. Furthermore, when the bit duplication of the tagID is higher, the proposed algorithm is more efficient than Query Tree algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.9
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• pp.29-37
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• 2004

In RFID system one of the problems that we must solve is to devise a good anti-collision algorithm to improve the efficiency of tag identification which is usually low because of tag collision. Among the existing RFID anti-collision algorithms, Framed Slotted ALOHA algorithm though simple, has a disadvantage that the number of slots used to identify the tags increases exponentially as the number of tags does. In the paper, we propose a new anti-collision algorithm called Partial-Response Framed Slotted ALOHA(PRFSA) which restricts the number of responding tags by dividing the tags into a number of groups when there are large number of tags and changes the frame size when there are small tags. Since the proposed algorithm keeps the frame size and the number of responding tags in such a way that can increase slot utilization, the algorithm shows superior performance to the existing ones. The simulation results showed that the proposed algorithm improves the slot efficiency by 85～100% compared to the existing algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.866-869
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• 2013

In this Paper, I propose a new anti-collision algorithm called Arbitrator-collision free reflected frame which restricts the size of frames and controlled the frame size when there are small tags. Since the proposal algorithm keeps the frame size and controlled the number of responding tags in such a way ones. can increase slot utilization, the algorithm shows superior performance to the existing algorithms. The simulation results showed that the proposed algorithm improves the efficiency by 0.8times compared to the existing algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.686-693
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• 2009

In this paper, we propose an efficient tag sleep method utilizing empty time slots for improving the tag collection performance in active RFID systems. In the proposed tag sleep method, the reader detects the occurrence of empty time slots by carrier sensing and utilizes the wasted empty time slots to transmit sleep commands to the collected tags throughout the framed slotted aloha-based tag collection process, resulting in reducing the time required for tag collection. Via the simulation experiments, we evaluated the performance of the tag collection applied with the proposed tag sleep method, compared with that of the basic tag collection. The simulation results showed that the tag collection applied with the proposed tag sleep method could reduce the average tag collection time by 12.28%, 12.30%, and 13.31 %, for the framed slotted aloha with the fixed 128 time slots and 256 time slots, and the dynamic framed slotted aloha anticollision protocols, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1889-1899
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• 2015

In this paper, we propose a multiple slot reservation scheme to transmit data rapidly in the satellite random access channel. In the R-CRDSA (Reservation scheme with Contention Resolution Diversity Slotted ALOHA), each satellite terminal can use only one slot in a frame. Therefore, many slots are wasting in the low traffic load and the satellite terminals which have large date needs many frame to transmit their data although there are unused slots. In the multiple slot reservation scheme, each satellite terminal transmits a packet with their data size and reserves many slots in the light of data size and slot reservation status. Therefore, each satellite terminal transmits their data faster than R-CRDSA. This is because they can reserve many slots in a frame. Furthermore, we simulate proposed scheme and validate the performance of proposed scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2103-2107
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• 2010

This paper deals with the recognition of multiple mobile robots equipped with RFID tag. In the case that the number of robots recognized by each RFID reader is larger than that of allocated slots, the clashing recognition occurs. And, in the case that the total number of robots recognized by all RFID reader is larger than that of real robots, the repetitious recognition occurs. We employ the dynamic frame slot allocation by using the ALOHA algorithm to prevent the clashing recognition and estimate the number of robots by using the received signal strength indication to prevent the repetitious recognition. The numerical experiment shows the reliability and the efficiency of the proposed method.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.677-681
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• 2010

This paper proposes a transmission probability control scheme for enhancing the performances of FSA-based RFID system. In order to maximize the system performance, the number of tags attempting to transmit their identifiers in a frame should be kept at a proper level. The reader calculates the transmission probability according to the number of tags within the identification range of reader and then broadcasts it to tags. Tags, in which their slot counter values reach to zero, attempt to transmit their identifiers with the received probability. Simulation results show that the proposed scheme can offer better throughput and delay performance than the conventional one regardless of the number of tags.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.518-527
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• 2008

Tag collection is one of the major functions in Radio Frequency Identification (RFID) systems. IS0/IEC 18000-7 defines the tag collection algorithm using the anti-collision algorithm, based on the framed slotted ALOHA for active RFID systems. However, it has inefficiency problems that reduce tag collection performance by deciding non-optimum slot size or using point-to-point commands to put collected tags to sleep. In this paper, we propose two mechanisms to overcome the inefficiency problems and improve tag collection performance: 1) a new slot size decision mechanism to allow the reader to choose the optimum slot size flexibly and 2) a broadcast-based sleep mechanism to put collected tags to sleep effectively. We also implemented an active RFID system, composed of an active RFID reader and multiple tags, and the reader is designed to maximize tag collection performance when the proposed mechanisms are applied. In experiments, we evaluated the tag collection performance using one reader and 50 tags in the real-world environment. The experimental results show that when two mechanisms are applied and the initial number of slots is chosen appropriately, the performance of the proposed tag collection algorithm is greatly enhanced, compared with that of the standard.