• Journal of the Korean Data and Information Science Society
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• v.17 no.4
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• pp.1261-1270
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• 2006

This paper proposes a mobile computing prefetching method providing the effective information about location change of mobile user or mobile computing in mobile information services. For mobile computing environments, there exist restrictions as like low bandwidth, latency and traffic. To solve those problems, a variety of techniques have been developed including caching and prefetching. In this paper we present a Statistical Poisson Prefetching Scheme using the reference count to provide a mobile user information that will be likely referenced in the near future. Comparing to existing methods in numerical results, the proposed method improves the prefetching performance to give the maximum effectiveness and reduces the failure rate of information searching.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.10
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• pp.1206-1216
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• 1999

이동 호스트란 시간과 공간의 제약 없이 필요한 기능을 수행하고, 또한 원하는 정보에 접근할 수 있는 휴대용 컴퓨터를 일컫는다. 이동 컴퓨팅 환경이란 이러한 이동 호스트들을 지원할 수 있도록 구성된 분산 환경이다. 따라서 이동 컴퓨팅 환경에서의 분산 알고리즘은 정적 호스트만을 고려한 기존의 분산 환경에서와는 다르게 이동 호스트의 여러 가지 특성들을 고려하여 제안되어야 한다. 즉, 이동 컴퓨팅 환경의 도래로 인하여 이동성과 휴대성, 그리고 무선 통신과 같은 특성들을 고려한 새로운 분산 상호 배제 알고리즘이 필요하다. 이제까지 이동 컴퓨팅 환경에서의 상호 배제 알고리즘은 토큰 링 구조에 기반을 두고 설계되었다. 토큰 링 구조는 이동 호스트들의 위치를 유지하기 위하여 높은 비용을 필요로 하는 단점을 가지고 있다. 본 논문에서는 균형 높이 트리(height-balanced tree)라는 새로운 모형을 제안함으로써 정적 분산 환경과 이동 분산 환경이 혼합된 환경에서 상호 배제 비용을 감소시킬 수 있는 새로운 알고리즘을 제안하며, 각 경우에 있어서의 비용을 산출하고 평가한다.Abstract The mobile host is a potable computer that carries out necessary functions and has the ability to access desirable informations without any constraints in time and space. Mobile computing environment is a distributed environment that is organized to support such mobile hosts. In that environment, distributed algorithms of which environment not only with static hosts but with mobile host's several properties should be proposed. With the emergence of mobile computing environments, a new distributed mutual exclusion method should be required to consider properties mobile computing system such as mobility, portability, and wireless communication. Until now, distributed mutual exclusion methods for mobile computing environments are designed based on a token ring structure, which have the drawbacks of requiring high costs in order to locate mobile hosts. In this paper, we propose a distributed mutual exclusion method that can reduce such costs by structuring the entire system as a height-balanced tree for static distributed networks and for networks with mobile hosts. We evaluated the operation costs in each case.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1932-1940
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• 2000

We must solve problems caused by mobile computing environments for supporting efficient mobile computing services. The problem is the use of wireless medium having high error rates and low bandwidth, and the sudden network disconnection to reduce the power consumption of a mobile host and the cost of the network connection. For these problems, we proposed the architecture of the partial connection manager and designed and implemented that in this paper. In particular, The partial connection manager creates the limited number of mobile agents according to priority and sends them in parallel to server systems and combines results of them process rapidly the user request. By applying the proposed partial connection manager to the mobile computing services called cybermarket, we knew that the mobile agent technique could be suited to the mobile computing environment and overcome the partial connection problem caused by eh mobile computing environment.

• Journal of Digital Contents Society
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• v.19 no.6
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• pp.1027-1032
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• 2018

Recently, new content for e-leisure, including e-sports and e-games, has become necessary. To meet this requirement, e-leisure mobile AR studies which track human are underway. The tracking performance at long distances is important because e-leisure mobile AR is used in outdoor environments. However, conventional mobile AR applications such as SNOW and Snapchat have the disadvantage of low tracking performance at long distances. Therefore, we propose an e-leisure mobile AR in outdoor environments. The proposed e-leisure mobile AR can estimate the position of the head in outdoor environments at long distances by using color markers and the human body ratio, and then augment a virtual object at the estimated position. The performance of the proposed e-leisure mobile AR was evaluated by measuring the tracking performance and processing time.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.32-39
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• 2009

Most mobile devices provide limited input interfaces in order to maximize the mobility and the portability. In this paper, the author proposes a small cubic-shaped tangible input interface which tracks the location, the direction, and the velocity using MEMS sensor technology to overcome the physical limitations of the poor input devices in mobile computing environments. As the preliminary phase for implementing the proposed tangible input interface, the prototype design and implementation methods are described in this paper. Various experiments such as menu manipulation, 3-dimensional contents control, and sensor data visualization have been performed in order to verify the validity of the proposed interface. The proposed tangible device enables direct and intuitive manipulation. It is obvious that the mobile computing will be more widespread and various kinds of new contents will emerge in near future. The proposed interface can be successfully employed for the new contents services that cannot be easily implemented because of the limitation of current input devices. It is also obvious that this kind of interface will be a critical component for future mobile communication environments. The proposed tangible interface will be further improved to be applied to various contents manipulation including 2D/3D games.

• Journal of KIISE:Software and Applications
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• v.30 no.7_8
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• pp.780-791
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• 2003

Caching is a useful technique to improve the response time by reducing contention of requests in mobile computing environments with a narrow bandwidth. in the traditional cache-based systems, to improve the hit ratio has been usually one of main concerns for the time. However, in mobile computing environments, it is necessary to consider the cost of cache miss as well as the hit ratio. In this paper, we propose a new cache replacement strategy in pull-based data dissemination systems. Then, we evaluate performance of the proposed strategy by a simulation approach. The proposed strategy considers both the popularity and the wating time together, so the page with the smallest value of multiplying popularity by waiting time is selected as a victim.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.149-159
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• 2011

Recently, mobile computing environments are becoming rapidly common. This trend emphasizes the necessity of accessing database systems on fixed networks from mobile platforms via wireless networks. However, it is not an appropriate way that applies the database access methods for traditional computing environments to mobile computing environments because of their essential restrictions. This paper suggests a new agent-based mobile database access model and also two functions calculating data significance scores to choose suitable data items for cache replacement and coherence policies. These functions synthetically reflect access term, access frequency and tendency, update frequency and tendency, and data item size distribution. As the result of simulation experiment, our policies outperform LRU, LIX, and SAIU policies in aspects of decrement of access latency, improvement of cache byte hit ratio, and decrease of cache byte pollution ratio.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.547-565
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• 2012

The design, development and deployment of Mobile Agent (MA) systems for high-level inference and surveillance in wireless sensor networks and RFID systems have drawn increasing attention in the past decade. To answer how the state-of-the-art of MA in a wide range of ubiquitous and sensor environments is, this paper investigates the current progress of MA. It proposes a taxonomy, by which MA systems in ubiquitous computing environments are decomposed and discussed. Then, this paper provides insights into the strengths and weaknesses of existing efforts. Finally, it presents a series of solutions from the viewpoint of various roles of MA in ubiquitous environments and situations.

• ETRI Journal
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• v.40 no.6
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• pp.813-823
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• 2018

In existing mobile computing environments, users need to choose between their privacy and the services that they can receive from an application. However, existing mobile platforms do not allow users to perform such trade-offs in a fine-grained manner. In this study, we investigate whether users can effectively make utility-privacy trade-offs when they are provided with a multilevel privacy control method that allows them to recognize the different quality of service that they will receive from an application by limiting the disclosure of their private information in multiple levels. We designed a research model to observe users' utility-privacy trade-offs in accordance with the privacy control methods and other factors such as the trustworthiness of an application, quality level of private information, and users' privacy preferences. We conducted a user survey with 516 participants and found that, compared with the existing binary privacy controls, both the service utility and the privacy protection levels were significantly increased when the users used the multilevel privacy control method.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1279-1289
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• 2000

Recently, research activities for combining portable computer technology and wireless communication technology are in progress to realize mobile computing environment that designed to support mobile hosts in the existing network environments. For PCN environments, the location management strategies are particularly emphasized among various strategies necessary for the mobile computing environment. Location management strategy for PCN environment, which is mostly based on the IS-41 standards brings an issue that additional network traffics are generated to deliver updata messages to home location server whenever a mobile host changes its location server. In this paper, we propose an innovative updata strategy and a search strategy that resolves the problem shown in the IS-41 scheme for HLR/VLR structure of CDMA environments. Also, this paper presents the performance comparison of proposed scheme and scheme used in IS-41 obtained from a simulation. The simulation was conducted based on the number of messages, the rate of database accesses, and the number of hops visited when the location management scheme is executed.