• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.165-182
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• 2014

An RFID systems employ efficient Anti-Collision Algorithms (ACAs) to enhance the performance in various applications. The EPC-Global G2 RFID system utilizes Frame Slotted Aloha (FSA) as its ACA. One of the common approaches used to maximize the system performance (tag identification efficiency) of FSA-based RFID systems involves finding the optimal value of the frame length relative to the contending population size of the RFID tags. Several analytical models for finding the optimal frame length have been developed; however, they are not perfectly optimized because they lack precise characterization for the timing details of the underlying ACA. In this paper, we investigate this promising direction by precisely characterizing the timing details of the EPC-Global G2 protocol and use it to derive a precise-optimal frame length model. The main objective of the model is to determine the optimal frame length value for the estimated number of tags that maximizes the performance of an RFID system. However, because precise estimation of the contending tags is difficult, we utilize a parametric-heuristic approach to maximize the system performance and propose two simple schemes based on the obtained optimal frame length-namely, Improved Dynamic-Frame Slotted Aloha (ID-FSA) and Exponential Random Partitioning-Frame Slotted Aloha (ERP-FSA). The ID-FSA scheme is based on the tag set estimation and frame size update mechanisms, whereas the ERP-FSA scheme adjusts the contending tag population in such a way that the applied frame size becomes optimal. The results of simulations conducted indicate that the ID-FSA scheme performs better than several well-known schemes in various conditions, while the ERP-FSA scheme performs well when the frame size is small.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.33-41
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• 2008

As RFID technology is developing and increasingly being used in many applications, the implementation is changing from single reader to multiple readers even dense readers. Since the number of readers is increasing, there are more collisions between readers and much interference between readers and tags. Therefore, to avoid interference or collision, many algorithms have being proposed, such as Gen2 dense mode, LBT(listen before talk), TDMA based method. In this paper, we propose a null frame algorithm, which calculates the collision probability in frame slotted aloha scheme and use this information to avoid the possible collisions. Comparing with conventional scheme, our proposed algorithm has some advantages in terms of reader collision number and required frame numbers.

• 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.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.1929-1945
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• 2011

RFID technologies have attracted a lot of attention in recent years because of their cost/time-effectiveness in large-scale logistics, supply chain management (SCM) and other various potential applications. One of the most important issues of the RFID-based systems is how quickly tags can be identified. Tag collision arbitration plays a more critical role in determining the system performance especially for passive tag-based ones where tag collisions are dealt with rather than prevented. We present a novel tag collision arbitration protocol called Optimum Frame-Slotted Aloha (OFSA). The protocol has been designed to achieve time-optimal efficiency in tag identification through an analytic study of tag identification delay and tag number estimation. Results from our analysis and extensive simulations demonstrate that OFSA outperforms other collision arbitration protocols. Also, unlike most prior anti-collision protocols, it does not require any modification to the current standards and architectures facilitating the rollout of RFID systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1517-1530
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• 2017

Traditional anti-collision algorithms determine slot size of initial frame based on the information of number of collision slots, idle slots, and success slots. Since there is no information about collision at the beginning of tag information collection, traditional anti-collision algorithms can not determine the initial frame size. Considering that performance of anti-collision algorithm is very sensitive to initial slot size traditional anti-collision algorithms need some improvements. In this study two methods are proposed to determine slot size of initial frame efficiently, through which we can improve the performance of dynamic frame slotted aloha algorithm. To verify the performance of proposed algorithms, 2.4GHz RFID system is used. Throughput and delay time are derived through simulation, which is developed using JAVA. We have seen that proposed algorithm improves throughput by 9.6% and delay time by 9.8%.

• 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.

• 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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.1
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• pp.129-133
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• 2005

Slotted ALOHA(S-ALOHA) is widely used in local wireless network. We analyze the performance of contention-based model in wireless LAN using S-ALOHA protocol. We analyze the performance of binary exponential backoff (BEB) algorithm under the slotted ALOHA protocol: whenever a node's message which tries to reserve a channel is involved in a collision for the ith time, it chooses one of the next $2^i$ frames with equal probability and attempts the reservation again. We derive the expected access delay and throughput which is defined as the expected number of messages that reserve a channel in a frame. A simulation study is performed to verify our method.

• ETRI Journal
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• v.37 no.5
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• pp.929-939
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• 2015

Ultra-high-frequency radio-frequency identification (UHF RFID) is widely applied in different industries. The Frame Slotted ALOHA in EPC C1G2 suffers severe collisions that limit the efficiency of tag recognition. An efficient full-duplex anti-collision scheme is proposed to reduce the rate of collision by coordinating the transmitting process of CDMA UWB uplink and UHF downlink. The relevant mathematical models are built to analyze the performance of the proposed scheme. Through simulation, some important findings are gained. The maximum number of identified tags in one slot is g/e (g is the number of PN codes and e is Euler's constant) when the number of tags is equal to mg (m is the number of slots). Unlike the Frame Slotted ALOHA, even if the frame size is small and the number of tags is large, there aren't too many collisions if the number of PN codes is large enough. Our approach with 7-bit Gold codes, 15-bit Gold codes, or 31-bit Gold codes operates 1.4 times, 1.7 times, or 3 times faster than the CDMA Slotted ALOHA, respectively, and 14.5 times, 16.2 times, or 18.5 times faster than the EPC C1 G2 system, respectively. More than 2,000 tags can be processed within 300 ms in our approach.

• 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.