• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.115-118
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• 2010

최근 RFID (Radio Frequency Identification)기술은 다양한 분야에서 관심을 받고 사용되고 있으며 RFID 리더의 종류도 매우 다양하다. 이러한 RFID 리더들을 지원하기 위해 RFID 미들웨어는 리더에서 지속적으로 발생하는 데이터를 수집, 제어, 관리하는 기능을 가지고 있으며 다양한 형태의 RFID 리더 인터페이스를 지원하여 이기종 RFID 리더와의 연동을 용이하게 한다. 현재 표준 규약에 따른 RFID 미들웨어들이 개발되고 있으며 RFID 표준 단체인 EPCglobal에서는 EPC (Electronic Product Code) 처리 시스템에서 RFID 태그를 인식한 리더가 애플리케이션 계층으로 데이터를 전달하는 역할을 하는 ALE (Application Level Events)라는 RFID 미들웨어를 제시하였다. 그러나 표준을 따르는 RFID 미들웨어는 그 자체가 복잡하고 부피가 크며 가격이 높기 때문에 이를 기반으로 한 시스템은 개발 속도가 늦어지고, 유지보수가 힘들어진다. 따라서 한 기업 내에서 사용되는 애플리케이션의 크기가 소규모 또는 중규모인 경우를 위해 보다 가벼운 RFID 미들웨어가 필요하다. 본 논문에서는 다양한 RFID 리더를 처리하기 위한 리더 매니저와 애플리케이션의 목적에 맞는 이벤트를 생성하는 쿼리 매니저를 가진 경량의 RFID 미들웨어를 개발하고자 한다. 리더 매니저는 RFID 리더를 관리하기 위한 추상 어댑터를 제공하고 리더 구성 XML 파일을 이용하여 RFID 리더를 관리한다. 쿼리 매니저는 질의 조건을 주기적으로 체크하는 스케줄러를 통해 RFID 이벤트를 관리한다. 본 경량적 RFID 미들웨어는 하드웨어의 투명성을 지원하며, 유지보수가 용이하고 유연성과 확장성을 제공하는 RFID 애플리케이션을 개발할 수 있도록 해준다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.404-412
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• 2011

More recently, variety RFID (Radio Frequency Identification) readers are produced by RFID equipment manufactures. Although a transmission standard instituted by EPCglobal is proposed for data transmission between the RFID readers and tags, other RFID reader protocols and the communication connection methods are be in use in other RFID companies. To replace or add the RFID readers of an RFID system, the developers should make changes to the core of the application and/or middleware. In this paper, we propose an RFID reader framework which can manage RFID readers without having to make changes the code of the application in environment with the growing number of heterogeneous RFID readers.This framework that sits on the layer between the RFID readers and the applications provides transparency to the RFID readers. Additionally, it can be used for monitoring the state and the property of all connected RFID, and for recording the RFID tag event logs and system logs. By using this framework, heterogeneous readers can be replaced and added without writing additional code in the applications. Consequently the readers can be easily managed and controlled by the RFID system administrator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10B
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• pp.1159-1167
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• 2011

In this paper, we proposed and implemented an EPCglobal Reader Manegement (RM) based management protocol. Using RFID Reader's management function, we could diagnose an active RFID Reader concretely which was impossible with only using Reader protocols and check the problem quickly when the RFID Reader is in failure. When diagnosing RFID Readers using the proposed RM based management protocol, we can check on their failure in stages and specifically, and can estimate range of failure. This helps RFID Reader's fast recovery, reduce loss of failure and improve QoS. We could get reader information with almost same overhead compared with the management message in LLRP. And we could get more information about RFID Reader's operation status.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.501-509
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• 2010

In this paper, the interference avoidance performance of the RFID reader with the compressive receiver was analyzed. In the environment of the multiple dense readers operating, the recognition rates of the conventional RFID reader and the proposed RFID reader with the compressive receiver were measured and compared. The recognition rate of the proposed reader was improved more than 2.7 times compared to the conventional reader. Especially, in the environment of two proposed RFID readers operating simultaneously, little degradation of the recognition rate was observed.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.55-64
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• 2009

For realizing ubiquitous computing, many research activities are geared towards various areas including embedded computing, RFID, USN, home networking, context-awareness, and etc. By using the ability of RFID technology to recognize a number of objects simultaneously, more convenient ubiquitous application services are effectively provided. In this case, RFID middleware playing a role as a bridge between RFID reader devices and application services is required as well. In this paper, we propose a method of handling a number of types of RFID reader devices in ALE middleware of EPCglobal. For this, the information of connection and data protocol for a reader device is stored in a database as ontology meta-data, and used to interpret the data read by a reader device. By adding ontology data into a database, even though an RFID device newly emerges, ALE middleware can not only handle the device, but also be effectively extended through reusing ontology data, without any changes in the middleware.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.85-94
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• 2008

When an RFID reader uses the same frequency or adjacent frequency with neighbor readers, the interference might occur. These interferences cause the RFID reader collision and errors during tag recognition. Therefore, the international standard for RFID and some papers proposed the methods to reduce the reader collision. The reader interference is closely related to the distance between the readers haying interference and used frequency band. In the previous RFID reader anti-collision algorithms, the location of readers inducing interference which is closely related to interference of readers is not considered. Only the reader collision is tried to reduce through frequency transfer after collisions occur or modification of frame size in relation to collision probability based a TDM(Time Division Multiplex). In this paper, the genetic algorithm using two-dimensional chromosome which reflect readers' location is proposed to prevent reader collision effectively. By executing evolutionary operation with two-dimensional chromosome, the location information having influence on reader interference can be used. The repair operation in the proposed algorithm makes all reader stably recognize their tags.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2007.05a
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• pp.239-245
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• 2007

차세대 유비쿼터스 환경에서 중요한 기술적, 산업적 위치를 차지하는 RFID 네트워크에는 다수의 RFID 리더(Reader)와 수많은 RFID 태그(Tag)들이 통신을 하면서 존재하게 된다. 이러한 RFID 네트워크에서 리더와 태그간의 원활한 통신을 위해서는 주파수 충돌이 발생하지 않아야 한다. 주파수 충돌 현상은 리더와 다수의 태그들 간의 태그 충돌(Tag Collision)과 리더간 주파수 간섭으로 인한 리더간 충돌(Reader Collision)로 나뉘어 질 수 있다. 따라서 리더간 충돌 현상을 피하기 위해서는 근접한 리더들 간에 서로 다른 타임슬롯(Timeslot)을 사용하여 태그와 통신을 시도하여야 한다. 본 연구에서는 RFID 네트워크에서 다수의 리더간 충돌을 최소화하며 안전한 태그 인식을 할 수 있도록 타임 슬롯 할당 문제를 CSP(Constraint Satisfaction Problem)로 접근한다. 그리고 CSP를 풀기 위해 리더간 충돌 문제가 가지고 있는 제약조건을 찾아내고 해를 찾기 위한 목적함수를 모델링 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8B
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• pp.822-829
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• 2009

A reader protocol is an interface between a host and RFID readers. There are several standards for reader protocol such as EPCglobal Low Level Reader Protocol (LLRP) 1.0.1, EPCglobal Reader Protocol (RP) 1.1, and ISO/IEC 15961/15962. Unfortunately, these standards focus on the passive RFID system, and so they are not appropriate for the active RFID system. In this paper, we implemented an efficient reader protocol for the active RFID system, which is based on EPCglobal LLRP 1.0.1, but smoothing/filtering functions of EPCglobal RP 1.1 are added. This protocol is designed to configure air interface parameters for active RFID readers and tags. It can reduce the amount of data transfer between the reader and host by filtering function, and can improve the performance of tag collection by smoothing function. In addition, it can remove inefficiency caused by tag memory data change according to the standards of ISO/IEC 15961/15962. In the real-world environment, we evaluated the performance of our implemented reader protocol using one RFID reader and 45 tags.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.51-60
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• 2009

In radio frequency identification(RFID) systems, when an RFID reader uses the same or adjacent frequency with neighbor readers, the interference between the readers may occur, which causes the reader collision and errors in tag recognition. In the previous study on RFID reader anti-collision, the techniques based on Frequency Division Mutiplex(FDM) or Time Division Multiplex(TDM) are proposed. However in these paper, the problem on the condition of RFID reader-to-reader interference considering the distance between interfering readers, frequency and operating time is not define exactly. In this paper, the interference effect is analyzed through RFID reader interference model considering the TDM and FDM, and the optimization problem is defined. To solve this, genetic-resource allocation technique is proposed. Therefore the optimal resource allocation applied RFID environment faithfully is accomplished.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10B
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• pp.885-893
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• 2008

In RFID system, reader collision happened when multiple readers try to read the tags at the same time. Because reader collision reduces tag recognition performance, it is required for RFID system to have reader anti-collision algorithm. In this paper, we propose reader anti-collision algorithm based on hierarchical structure, where a master reader controls the slave readers to avoid the reader collisions. It is verified through simulations that the proposed algorithm enhances the performance in terms of leader collision probability and tag reading time.