• 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 information and communication convergence engineering
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• v.12 no.1
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• pp.19-25
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• 2014

The wireless sensor networking standard DASH7 operates in low-power communication with a better transmission quality in active RFID networks. The DASH7 security standard supports public key cryptography. At present, the DASH7 standard uses the message authentication code in the network layer for authentication and integrity. However, its security standard is still in an incubation stage with respect to the implementation of a crypto exchange over a DASH7 network. Effective key management is an important factor for privacy and security. If organizations are not careful about where and how keys are stored, they leave the encrypted data vulnerable to theft. In this regard, we present a key management system designed for efficient key management through public key infrastructure authentication as well as a non-repudiation feature for the DASH7 standard. We analyze the performance of the proposed system on a basis of various performance criteria such as latency and throughput.

• Journal of Korea Spatial Information System Society
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• v.11 no.1
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• pp.127-136
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• 2009

This paper proposes an on-line mining algorithm of moving trajectory patterns in RFID data streams considering changing characteristics over time and constraints of single-pass data scan. Since RFID, sensor, and mobile network technology have been rapidly developed, many researchers have been recently focused on the study of real-time data gathering from real-world and mining the useful patterns from them. Previous researches for sequential patterns or moving trajectory patterns based on stream data have an extremely time-consum ing problem because of multi-pass database scan and tree traversal, and they also did not consider the time-changing characteristics of stream data. The proposed method preserves the sequential strength of 2-lengths frequent patterns in binary relationship table using the time-evolving graph to exactly reflect changes of RFID data stream from time to time. In addition, in order to solve the problem of the repetitive data scans, the proposed algorithm infers candidate k-lengths moving trajectory patterns beforehand at a time point t, and then extracts the patterns after screening the candidate patterns by only one-pass at a time point t+1. Through the experiment, the proposed method shows the superior performance in respect of time and space complexity than the Apriori-like method according as the reduction ratio of candidate sets is about 7 percent.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.113-122
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• 2008

In RFID system, Middleware collects and filters streaming data gathered continuously from readers to process applications requests. The enormous amount of data makes middleware in highly overloaded. Hence, we propose reader level filtering in order to reduce overall middleware load. In this paper, we consider reader filtering capability and define query plan to minimize number of queries for processing into middleware and reader level. We design and implement middleware system based on proposed query plan. We perform several experiments on implemented system. Our experiments show that the proposed query plan considerably improves the performance of middleware by diminishing processing time and network traffic between reader and middleware.

• Journal of Biosystems Engineering
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• v.33 no.3
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• pp.204-209
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• 2008

The power strength of electric wave of reader looked radiation forms from the gate type RFID system. The more distant from antennas, the weaker of power strength of electric wave. The power strength of electric wave with 3 antennas showed stronger than its with 2 antennas. With 2 antennas, the coefficient of correlation between the power strength of electric wave and response ability of tag was 0.665 (p=0.009), and it showed results at significance level. With 3 antennas, the coefficient of correlation was 0.711 (p=0.004), correlationship between the power strength of electric wave and the response ability of tag showed at significance high level. From the analysis result about tag reading performance on the gate type RFID system, the reading rate was good when tags were attached on a acrylic plate which were located in front of 3 or 4 antennas. As tags were getting away from antennas, the reading rate was decreased. The nearer from antennas, the higher the reading rate at the center. When tags were turned at right angles with antennas, the longer distant from antennas, the lower reading rates at the center, right and left locations. When the number of antennas and distance are constant, respectively, the significant difference of the tag reading rates according to the locations of left, right and center were not found.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.731-736
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• 2017

In this paper, we propose a simplified tag collection algorithm to improve the performances of ISO/IEC 18000-7, which is a standard for an active RFID system. The proposed algorithm modifies the collection command that enables to start a tag collection round. The modified collection command includes the results of the listen period response for the previous collection round. Tags that receive the collection command check the collision status for their responses. If there is no collision, tags transmit their additional data and go into the sleep mode without the point-to-point read command and sleep command. A collection round for the standard consists of a collection command and response, a read command and response, and sleep command. On the other hand, in the proposed algorithm, a collection round consists of a collection command and response. The simulation results showed that the proposed algorithm can improve the identification delay about 16% compared with the standard when the number of tags are 300.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.203-208
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• 2014

In this paper, the antenna of a small active RFID for 433MHz is proposed, and the proposed antenna is a kind of built-in antenna, which uses IFA structure. The performance was improved by the change of the spacing between the feed point and short strip, inserting the meander line structure in a radiator, and varying the gap between the radiator and the ground plane in the proposed antenna. To confirm the characteristics of the antenna parameters, HFSS from ANSYS Inc. was used for the analysis. The frequency band of 433MHz Active RFID is from 433.67 to 434.17 MHz. There is a value of return loss less than -9.54 dB in 433MHz band of the active RFID, and the maximum antenna gain is -4.28dBi. The Jig size of the proposed antenna is $72{\times}44{\times}1mm$, and the size of the antenna area is $35.5{\times}19.5mm$. The result proved the possibility of the practical use on miniaturized 433MHz antenna using IFA structure that came from comparing and analyzing the measured and simulated data of the antenna.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.143-146
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• 2008

For tracing tag locations, a trajectories should be modeled and indexed in radio frequency identification (RFID) systems. The trajectory of a tag can be represented as a line that connects two spatiotemporal locations captured when the tag enters and leaves the vicinity of a reader. If a tag enters but does not leave a reader, its trajectory is represented only as a point captured at entry and we should extend the region of a query to find the tag that remains in a reader. In this paper, we propose an interval data model of tag's trajectory in order to solve the problem. For the interval data model. we propose a new index scheme called the IR-tree(Interval R-tree) and algorithms of insert and split for processing query efficiently. We also evaluate the performance of the proposed index scheme and compare it with the previous indexes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.578-581
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• 2007

For tracing tag locations, a trajectories should be modeled and indexed in radio frequency identification (RFID) systems. The trajectory of a tag can be represented as a line that connects two spatiotemporal locations captured when the tag enters and leaves the vicinity of a reader. If a tag enters but does not leave a reader, its trajectory is represented only as a point captured at entry. Because the information that the tag stays in the reader is missing from the trajectory represented only as a point, we should extend the region of a query to find the tag that remains in a reader. In this paper, we propose an interval data model of tag's trajectory in order to solve the problem. Trajectories of tags are represented as two kinds of intervals; dynamic intervals which are time-dependent lines and static intervals which are fixed lines. We also show that the interval data model has better performance than others with a cost model

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.1
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• pp.113-120
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• 2009

Through the automatic sensing of the environment, USN technology can give the best services. In this work, we have developed an active RFID system and examined its performance. By implementing it into water quality sensors, we constructed a system that can detect diverse indoor/outdoor environment and provide information about the pollution level obtained from the temperature and PH sensors. Our RF system had an internal Print-on-PCB antenna for the miniaturization of the tag. We used a RF transceiver CC2510 chipset of TI company to realize the active RFID function. By using RSSI constants obtained, we performed the evaluation of real time location accuracy with a software written in Labview. Among 10 arbitrary locations, we obtained average measurement errors of 1.69 m in x axis and 1.66 m in y axis. This technology can be applied to logistics, environmental monitoring, prevention of missing children and various applications.