• 한국컴퓨터정보학회논문지
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• 제14권1호
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• pp.183-190
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• 2009

유비쿼터스 컴퓨터 환경의 핵심기술은 상황인식 컴퓨팅기술로써 상황인식기술은 소프트웨어적 성격이 강하여 상황인식의 핵심엔진을 개발하고 이를 적용한 장치 개발이 주요 연구 작업이다. 유비쿼터스 컴퓨팅시대가 도래하면 기존의 인터넷 쇼핑몰에서 고객이 직접 상품을 검색하여 주문을 하는 형태에서 진화되어 상황인식 기술의 핵심기술인 지능형 에이전트 기술이 접목된 검색 엔진이 고객의 입력 정보를 조합하여 비교검색이 이루어진 후 추천하는 형태의 시스템으로 발전될 것이다. 본 논문에서는 사례기반 추론 기법 및 지능형 에이전트 기술을 기반으로 한 검색 엔진을 설계하고 인터넷 패션 상품 전문 몰에 적용하여 고객이 직접 상품을 검색하는 대신 지능형 에이전트가 검색하여 패키지 형태로 제공되는 주문형 맞춤식 패션 전문 시스템을 설계하고 프로토타입을 구현한다.

• 한국통신학회논문지
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• 제35권7B호
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• pp.1058-1065
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• 2010

최근 유비쿼터스 컴퓨팅과 유비쿼터스 네트워크를 활용하여 새로운 서비스들을 개발하려는 노력이 진행 중이며, 이에 관련된 기술의 중요성도 급증하고 있다. 특히 실내에서 사물의 정밀한 위치를 인식하는 기술은 유비쿼터스 서비스를 제공함에 있어 핵심 기술로 떠오르면서, 이에 대한 연구가 활발히 진행 중이다. 이러한 많은 관심에도 불구하고, 지금까지 실내 위치인식을 위한 시뮬레이션 툴은 그 중요성에 비해 연구가 미진한 실정이다. 본 논문에서는 고속의 근거리 무선 통신망을 제공할 수 있는 해결책으로 최근 각광을 받고 있는 UWB 무선 채널 상에서 정밀한 실내 위치인식을 위해 Ptolemy 툴을 이용한 범용적인 위치인식 시뮬레이터를 개발하고 다양한 위치인식 알고리즘들의 성능을 분석하고자 한다.

• ETRI Journal
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• 제29권5호
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• pp.545-558
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• 2007

This paper presents an efficient semantic service discovery scheme called UbiSearch for a large-scale ubiquitous computing environment. A semantic service discovery network in the semantic vector space is proposed where services that are semantically close to each other are mapped to nearby positions so that the similar services are registered in a cluster of resolvers. Using this mapping technique, the search space for a query is efficiently confined within a minimized cluster region while maintaining high accuracy in comparison to the centralized scheme. The proposed semantic service discovery network provides a number of novel features to evenly distribute service indexes to the resolvers and reduce the number of resolvers to visit. Our simulation study shows that UbiSearch provides good semantic searchability as compared to the centralized indexing system. At the same time, it supports scalable semantic queries with low communication overhead, balanced load distribution among resolvers for service registration and query processing, and personalized semantic matching.

• 제어로봇시스템학회논문지
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• 제12궈1호
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• pp.41-46
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• 2006

Ubiquitous location based services, offer helpful services anytime and anywhere by using real-time location information of objects based on ubiquitous network. Particularly, autonomous mobile robots can be a solution for various applications related to ubiquitous location based services, e.g. in hospitals, for cleaning, at airports or railway stations. However, a meaningful and still unsolved problem for most applications is to develop a robust and cheap positioning system. A typical example of position measurements is dead reckoning that is well known for providing a good short-term accuracy, being inexpensive and allowing very high sampling rates. However, the measurement always has some accumulated errors because the fundamental idea of dead reckoning is the integration of incremental motion information over time. The other hand, a localization system using RFID offers absolute position of robots regardless of elapsed time. We construct an absolute positioning system based on RFID and investigate how localization technique can be enhanced by RFID through experiment to measure the location of a mobile robot. Tags are placed on the floor at 5cm intervals in the shape of square in an arbitrary space and the accuracy of position measurement is investigated . To reduce the error and the variation of error, a weighting function based on Gaussian function is used. Different weighting values are applied to position data of tags since weighting values follow Gaussian function.

• Journal of Information Processing Systems
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• 제6권4호
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• pp.609-620
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• 2010

In order to provide a tailored education for learners within the ubiquitous environment, it is critical to undertake an analysis of the learning activities of learners. For this purpose, SCORM (Sharable Contents Object Reference Model), IMS LD (Instructional Management System Learning Design) and other standards provide learning design support functions, such as, progress checks. However, in order to apply these types of standards, contents packaging is required, and due to the complicated standard dimensions, the facilitation level is lower than the work volume when developing the contents and this requires additional work when revision becomes necessary. In addition, since the learning results are managed by the server there is the problem of the OS being unable to save data when the network is cut off. In this study, a system is realized to manage the actions of learners through the event interception of a web-browser by using event hooking. Through this technique, all HTMLbased contents can be facilitated again without additional work and saving and analysis of learning results are available to improve the problems following the application of standards. Furthermore, the ubiquitous learning environment can be supported by tracking down learning results when the network is cut off.

• 한국멀티미디어학회논문지
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• 제12권12호
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• pp.1769-1777
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• 2009

With the advent of the ubiquitous technology age, the progress of network technology has enabled a robust sensor communication, not just in cities, but also in poor surroundings such as deserts, polar regions, or underwater environments. In this paper, we propose a Multiple Acknowledgement (MA) technique to replace the conventional Automatic Repeat request (ARQ) technique. The MA mechanism is to send an Ack to many receivers simultaneously. The CH (master, coordinator) of the unit cluster broadcasts a Beacon frame where Ack information of the previously transmitted data is included. This technique can reduce the number of transmissions and overhead significantly. The proposed technique is a scheme improving the efficiency of an underwater sensor network where the uplink data transmission is the mainstream. The Performance of the ARQ, Block Ack, Pervasive Block Ack and the proposed method were compared with one another and analyzed. The proposed method showed significant performance improvement as compared with the ARQ, BA, and PBA in its channel efficiency.

• 한국지능시스템학회논문지
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• 제13권2호
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• pp.247-258
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• 2003

본 논문에서는 사용자가 2차원 또는 3차원 상에서 필기를 하는 경우의 관성치를 측정할 수 있는 가속도계와 각속도계를 장착한 펜형 입력 장치를 소개한다. 각속도계의 측정치를 한 번 적분해 시스템의 자세를 구하며 이는 가속도에 포함되어 있는 중력 가속도 성분을 제거하는 데 사용된다. 시스템의 위치는 보정된 가속도를 두 번 적분해 구한다. 이러한 원리는 관성 항법 시스템에서 보편적으로 사용되는 것이다. 그러나 필기 궤적을 복원하기 위해 사용되는 이중 적분 과정으로 인해 위치 측정치의 정확도는 시간이 지남에 따라 심각하게 떨어진다. 이러한 문제는 관성 항법 시스템에 있어 일반적인 경우이며 통상 외부의 기준 신호나 기타 정보를 이용한 주기적 또는 비주기적인 시스템의 교정을 통해 해결된다. 본 논문에서는 위치 및 속도의 보정은 온라인과 오프라인 교정 과정을 통해 이루어진다. 온라인 교정 과정에서는 칼만 필터를 이용한 보상 필터 기법을 사용한다. 오프라인 교정 과정에서는 최종적인 시스템의 항법 오차의 상수 성분을 속도 정보와 움직임 검지 알고리듬을 통해 제거한다. 실제 실험을 통해 제안된 시스템의 유용성과 효용성을 보인다.

• Journal of electromagnetic engineering and science
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• 제8권2호
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• pp.41-46
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• 2008

A bandwidth and power efficient high speed ubiquitous sensor network(USN) for realizing a ubiquitous society is a great challenge for researcher community. In this paper we incorporate a cooperative transmission protocol within a special type of multi-code modulation to meet these requirements. Multi-code(Mc) modulation has been developed for high-speed data transmission over wireless channels. We proposed a new class of orthogonal codes for multi-code modulation which is an orthogonal subset of orthogonal codes(OSOC). Our proposed OSOC structure allows us to use only one relay to cooperate M nodes that effectively reduces the bandwidth and power requirement. This protocol is similar to spread-spectrum(SS) technique that can reduce both broad and narrow band jamming.

• 전기학회논문지
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• 제57권10호
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• pp.1790-1795
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• 2008

Energy scavenging is a technique that converts ambient energy, for example, vibration and light, to electrical energy in order to supply power to low power electronic devices such as ubiquitous sensors. In this paper, we propose an optimal operation condition of power delivery circuit and design strategy for energy scavenging system in which the generated power is order of microwatt and, consequently, efficient handling of power is critical. We also propose that high data transmission rate is more realistic optimal design objective rather than high energy efficiency. It is shown that disconnection of load from the storage capacitor right after data transmission reduces energy wasting and that optimal value of storage capacitor can be determined at this condition. The feasibility of our propose is proved by experiments and we believe that the proposed design strategy will promote the application of piezoelectric micropower generator to the ubiquitous sensor networks.

• 한국군사과학기술학회지
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• 제13권3호
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• pp.438-444
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• 2010

Surveillance and reconnaissance sensor network system is an application system based on ubiquitous sensor network technology. This technique is to avoid accidental close combat, to minimize the consumption of limited military resources and personnel, and to provide battlefield situational awareness information for the unit's future combat missions. In this paper, we have proposed a echelons scale identification scheme based on information obtained from surveillance and reconnaissance sensor network system.