• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.5
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• pp.9-20
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• 2005

In this paper, we propose ubiTrack, a system which tracks users' location in indoor environments by employing infrared-based proximity method. Most of recently developed systems have focussed on performance and accuracy. For this reason, they adopted the idea of centralized management, which gathers all information in a main system to monitor users' location. However, these systems raise privacy concerns in ubiquitous computing environments where tons of sensors are seamlessly embedded into environments. In addition, centralized systems also need high computational power to support multiple users. The proposed ubiTrack is designed as a passive mobile architecture to relax privacy problems. Moreover, ubiTrack utilizes appropriate area as a unit to efficiently track users. To achieve this, ubiTrack overlaps each sensing area by utilizing the TDM (Time-Division Multiplexing) method. Additionally, ubiTrack exploits various filtering methods at each receiver and utilization module. The filtering methods minimize unexpected noise effect caused by external shock or intensity weakness of ID signal at the boundary of sensing area. ubiTrack can be applied not only to location-based applications but also to context-aware applications because of its associated module. This module is a part of middleware to support communication between heterogeneous applications or sensors in ubiquitous computing environments.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.723-727
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• 2006

애드혹 유비쿼터스 컴퓨팅 환경에서 상호작용 미들웨어는 컨텍스트의 변화에 따라 애플리케이션간의 상호작용을 재구성할 수 있도록 지원해야 한다. 또한 미들웨어는 컨텍스트 인지 상호작용을 지원하는데 있어 컨텍스트 종류나 애플리케이션들 혹은 환경의 다양성에 따라 컨텍스트 변화에 대한 적응성을 동적으로 변화시킬 수 있도록 기능을 제공해야 한다. 하지만 기존 연구들은 컨텍스트 변화에 대한 적응성을 변화시키는 이러한 요소들에 대해 고려하지 않으며 그로 인해 컨텍스트 변화에 대한 적응 정도를 정적으로 설정함으로써 컨텍스트 인지 상호작용을 지원하는데 있어 경우에 따라 오버헤드가 발생하거나 컨텍스트 변화에 빠르게 대응하지 못한다. 따라서 본 연구는 애드혹 유비쿼터스 컴퓨팅 환경에서 동작하는 Publish/Subscribe 기반의 상호작용 미들웨어에서 이벤트 중계의 정확성과 컨텍스트 변화 적응성간의 관계를 기반으로 다양한 컨텍스트 종류나 사용자, 환경에 따라 이벤트 중계의 정확도를 동적으로 조절하는 기법을 제안한다. 그리고 이를 기반으로 이벤트 중계 정보를 동적으로 재구성하여 컨텍스트에 맞춰 효율적으로 컨텍스트 인지 상호작용을 구성할 수 있는 기법을 제안한다. 비교 분석 결과 기존 연구에 비해 컨텍스트 변화에 대한 적응성에서 더 나은 결과를 보여주었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.35-43
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• 2004

An arbitration method is proposed to resolve a collision and arbitrate beacon transmissions in an indoor Positioning system consisting of multiple beacons and listeners. Although two or more beacons may compete to transmit signals simultaneously, a single winner in the competition is determined autonomously through the arbitration process while they are transmitting. So, it can continue to send its data, but the others give up their transmissions during the arbitration process. As a consequence, update rate for location information and channel utilization can be improved by avoiding that all beacons fail due to a collision. Once a beacon succeeds in transmitting its signal, a low-level priority is assigned to it. And a high-level priority is allocated to a beacon which gave up its transmission during arbitration process. This will guarantee every beacon has fair transmission opportunity with the arbitration method. As no centralized control is required among beacons, a Positioning system can still be easily deployed and expanded with this arbitration method.

• Journal of Intelligence and Information Systems
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• v.14 no.3
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• pp.1-23
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• 2008

Nowadays blogging is emerging as a new way of building human-to-human relationship by offering personal information and sharing opinions with others on their own initiatives. These blogging activities would be also useful when people are in a movement surrounding lots of objects, such as products and shops, which are potentially interesting to them. However, immediate response from the objects is not available using legacy blogging systems. This is mainly due to the segregation of the blogging content owners from the objects. This paper, hence, aims to propose a methodology which allows the users to directly communicate with the objects in a timely and context-aware manner, not the object owners, to get useful information or get served immediately. To do so, the concept of artificial bloggers which work on behalf of the objects and eventually the object owners is proposed. The functionalities of u-Blogging are also introduced with prototype system.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.923-930
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• 2004

Wireless sensor networks is a core technology of ubiquitous computing which enables the network to aware the different kind of context by integrating exiting wired/wireless infranet with various sensor devices and connecting collected environmental data with applications. However it needs an energy-efficient approach in network layer to maintain the dynamic ad hoc network and to maximize the network lifetime by using energy constrained node. Cluster-based data aggregation and routing are energy-efficient solution judging from architecture of sensor networks and characteristics of data. In this paper. we propose a new distributed clustering algorithm in using distance from the sink. This algorithm shows that it can balance energy dissipation among nodes while minimizing the overhead. We verify that our clustering is more en-ergy-efficient and thus prolongs the network lifetime in comparing our proposed clustering to existing probabilistic clustering for sensor network via simulation.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.2 s.314
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• pp.47-59
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• 2007

Recently, Healthcare system has not been standardized and has been developed as an embedded system lacking interoperability. We are finally going to face such problems as having excessive load in using network caused by the uncontrolled spread of system and un-guaranteed interoperability among the heterogeneous systems. We suggest the possibility that OSGi and JADE can be accepted as a solution for the above problems.

• The Journal of the Korea Contents Association
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• v.8 no.9
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• pp.19-26
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• 2008

With the development of ubiquitous computing and the construction of infrastructure for one-to-one personalized services, the importance of context-aware services based on user's situation and environment is being spotlighted. The smart home technology connects real space and virtual space, and converts situations in reality into information in a virtual space, and provides user-oriented intelligent services using this information. In this paper, we proposed the discovery of the behavior sequence pattern using the mining in the smart home. We discovered the behavior sequence pattern by using mining to add time variation to the association rule between locations that occur in location transactions. We can predict the path or behavior of user according to the recognized time sequence and provide services accordingly. To evaluate the performance of behavior consequence pattern using mining, we conducted sample t-tests so as to verify usefulness. This evaluation found that the difference of satisfaction by service was statistically meaningful, and showed high satisfaction.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.36-42
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• 2009

In the mobile device environment, the context-aware computing has been emerging as a core technology of ubiquitous computing. Compared with a desktop computer, a user interface and resource of mobile device is very limited. Traditional desktop-based user interface has been developed on the basis that a user's activity is static state. In contrast, mobile devices are not able to utilize representative desktop-based interaction mechanisms such as a keyboard and mouse, not only because the activity of a user is dynamic state, but mobile devices have limited resources and small LCD display. In this paper, we introduce an intelligent control system for the mobile device that can utility effectively the limited resource and complement the poor user interface by using an accelerometer being able to sense the physical activity and posture. The proposed system can estimate the user activity, static and dynamic states, and posture watching the PDA at the same time, and the proposed intelligent control system as its application, the backlight ON/OFF on the PDA, is run by the result of the user's behavior.

• Journal of Intelligence and Information Systems
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• v.17 no.3
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• pp.43-61
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• 2011

In this research, we propose a dynamic decision making using social context based on ontology. Dynamic adaptation is adopted for the high qualified decision making, which is defined as creation of proper information using contexts depending on decision maker's state of affairs in ubiquitous computing environment. Thereby, the context for the dynamic adaptation is classified as a static, dynamic and social context. Static context contains personal explicit information like demographic data. Dynamic context like weather or traffic information is provided by external information service provider. Finally, social context implies much more implicit knowledge such as social relationship than the other two-type context, but it is not easy to extract any implied tacit knowledge as well as generalized rules from the information. So, it was not easy for the social context to apply into dynamic adaptation. In this light, we tried the social context into the dynamic adaptation to generate context-appropriate personalized information. It is necessary to build modeling methodology to adopt dynamic adaptation using the context. The proposed context modeling used ontology and cases which are best to represent tacit and unstructured knowledge such as social context. Case-based reasoning and constraint satisfaction problem is applied into the dynamic decision making system for the dynamic adaption. Case-based reasoning is used case to represent the context including social, dynamic and static and to extract personalized knowledge from the personalized case-base. Constraint satisfaction problem is used when the selected case through the case-based reasoning needs dynamic adaptation, since it is usual to adapt the selected case because context can be changed timely according to environment status. The case-base reasoning adopts problem context for effective representation of static, dynamic and social context, which use a case structure with index and solution and problem ontology of decision maker. The case is stored in case-base as a repository of a decision maker's personal experience and knowledge. The constraint satisfaction problem use solution ontology which is extracted from collective intelligence which is generalized from solutions of decision makers. The solution ontology is retrieved to find proper solution depending on the decision maker's context when it is necessary. At the same time, dynamic adaptation is applied to adapt the selected case using solution ontology. The decision making process is comprised of following steps. First, whenever the system aware new context, the system converses the context into problem context ontology with case structure. Any context is defined by a case with a formal knowledge representation structure. Thereby, social context as implicit knowledge is also represented a formal form like a case. In addition, for the context modeling, ontology is also adopted. Second, we select a proper case as a decision making solution from decision maker's personal case-base. We convince that the selected case should be the best case depending on context related to decision maker's current status as well as decision maker's requirements. However, it is possible to change the environment and context around the decision maker and it is necessary to adapt the selected case. Third, if the selected case is not available or the decision maker doesn't satisfy according to the newly arrived context, then constraint satisfaction problem and solution ontology is applied to derive new solution for the decision maker. The constraint satisfaction problem uses to the previously selected case to adopt and solution ontology. The verification of the proposed methodology is processed by searching a meeting place according to the decision maker's requirements and context, the extracted solution shows the satisfaction depending on meeting purpose.

• The KIPS Transactions:PartD
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• v.13D no.6 s.109
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• pp.839-846
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• 2006

Context-aware adaptive service for overcoming the limitations of wireless devices and maintaining adequate service levels in changing environments is becoming an important issue. However, most existing studies concentrate on an adaptation module on the client, proxy, or server. These existing studies thus suffer from the problem of having the workload concentrated on a single system when the number of users increases md, and as a result, increases the response time to a user's request. Therefore, in this paper the adaptation module is dispersed and arranged over the client, proxy, and server. The module monitors the contort of the system and creates a proposition as to the dispersed adaptation system in which the most adequate system for conducting operations. Through this method faster adaptation work will be made possible even when the numbers of users increase, and more stable system operation is made possible as the workload is divided. In order to evaluate the proposed system, a prototype is constructed and dispersed operations are tested using multimedia based learning content, simulating server overload and compared the response times and system stability with the existing server based adaptation method. The effectiveness of the system is confirmed through this results.