• Journal of KIISE:Computer Systems and Theory
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• v.27 no.1
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• pp.89-100
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• 2000

Recently, studies on the mobile computing environments that enable mobile hosts to move while retaining its network connection are in progress. In these mobile computing environments, one of the necessary components is the distributed file system supporting mobile hosts, and there are several issues for the design and implementation of the shared file system. Among these issues, there are problems caused by network traffic on limited bandwidth of wireless media. Also, there are consistency maintenance issues that are caused by update-conflicts on the shared files in the distributed file system. In this paper, we propose TWB(Trickle Write-Back) scheme that utilizes weak connectivity for cache management of mobile clients. This scheme focuses on saving bandwidth, reducing waste of disk space, and reducing risks caused by disconnection. For such goals, this scheme lets mobile clients write back intermediate states periodically or on demand while delaying unnecessary write-backs. Meanwhile, this scheme is based on the existing distributed file system architecture and provides transparency.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.651-653
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• 2003

As a result of the project 'Development of core technology for open LBS', we developed several solutions such as personal navigation system, mobile game, and emergency system. In this paper, we explain the approach and architecture of these solutions and consider their meaning on spatial information bases and expectation in the future computing environments. The final goal of this suggested solution is to test the efficiency of our open LBS system and verify the applicability and usability in real application environments. Our approaches will be headed to the future ubiquitous computing environments.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.348-352
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• 2008

In distributed computing paradigm, mobile surrogate systems migrates from on host in a network to another. However, Mobile surrogate system have not gained wide acceptance because of security concerns that have not been suitably addressed yet. In this paper, we propose a security framework based on Grid Proxy Gateway for mobile Grid service. The current Grid Security Infrastructure is extended to mobile computing environments. The surrogate host system designed for mobile Personal Digital Assistant (PDA) users can access the certified host and get his proxy credential to launch remote job submission securely.

• The Transactions of the Korea Information Processing Society
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• v.7 no.9
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• pp.2969-2979
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• 2000

A mobile host has failure causes such as failure of the mobile host, disconnection of the mobile host, and wireless link failure that have not been seen in traditional computing environments. So far there have been few studies on fault tolerance of a mobile host in mobile computing environments. The Lazy scheme, a failure recovery technique of the mobile host, is a cost-effective one. However, this scheme has a defect that the mobile host cannot be recovered from failure of the base station with acheckpoint of the mobile host. In this paper, we propose and evaluate the Redundant Lazy scheme for performance improvement of the Lazy scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.2
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• pp.3-12
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• 2006

The spread of mobile devices, PDAs and sensors has enabled the construction of ubiquitous computing environments, transforming regular physical spaces into 'smart space' augmented with intelligence and enhanced with services. However, unless privacy concerns are taken into account early in the design process of various ubiquitous devices(e.g. mobile devices, PDAs, sensors, etc.). we will end up crating ubiquitous surveillance infrastructure. Also, it may inappropriate to use public key techniques for computational constrained devices in ubiquitous computing environment. In this paper, we propose efficient user authentication and ky agreement protocol not only to preserve anonymity for protecting personal privacy but also to be suitable for computational constrained devices in ubiquitous computing environments.

• ETRI Journal
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• v.37 no.2
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• pp.348-358
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• 2015

Mobile devices have been widespread and become very popular with connectivity to the Internet, and a lot of desktop PC applications are now aggressively ported to them. Unfortunately, mobile devices are often vulnerable to malicious attacks due to their common usage and connectivity to the Internet. Therefore, the demands on the development of mobile security systems increase in accordance with advances in mobile computing. However, it is very hard to run a security program on a mobile device all of the time due the device's limited computational power and battery life. To overcome these problems, we propose a novel mobile security scheme that migrates heavy computations on mobile devices to cloud servers. An efficient data transmission scheme for reducing data traffic between devices and servers over networks is introduced. We have evaluated the proposed scheme with a mobile device in a cloud environment, whereby it achieved a maximum speedup of 13.4 compared to a traditional algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.2
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• pp.21-30
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• 2000

본 논문에서는 이동통신환경의 특징과 기존의 키분배 프로토콜들에서 발생할 수 있는 공격들을 프로토콜 수행전 수행중, 수행후로 나누어서 살펴보고 이를 기반으로 이동통신환경에 적합한 키분배 프로토콜 설계에 필요한 요구사항 들을 제시한다 또한 제시된 요구사항을 기반으로 이동통신환경에 적합한 상호인증을 제공하는 키분배 프로토콜을 제안하고 제안한 프로토콜을 분석한다.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.78-92
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• 1999

In mobile computing environments, to efficiently use the narrow bandwidth of wireless networks a mobile host caches the data that are frequently accessed. To guarantee the correctness of the mobile transaction, the data cached in a mobile host must be consistent with the data in a server. This paper proposes a new strategy which maintains cache consistency efficiently when the data cached in a mobile host are inconsistent with the data in a server by the mobility of the mobile host at the asynchronous mobile environment. In this strategy, the size of the invalidation message is relatively small and is independent of the number of data to be invalidated under conditions of variable update rates/patterns. So this strategy uses the narrow bandwidth of wireless networks efficiently and reduces the communication cost.

• Journal of Information Processing Systems
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• v.13 no.4
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• pp.731-751
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• 2017

The burgeoning distribution of smartphone web applications based on various mobile environments is increasingly focusing on the performance of mobile applications implemented by JavaScript and HTML5 (Hyper Text Markup Language 5). If application software has a simple functional processing structure, then the problem is benign. However, browser loads are becoming more burdensome as the amount of JavaScript processing continues to increase. Processing time and capacity of the JavaScript in current mobile browsers are limited. As a solution, the Web Worker is designed to implement multi-threading. However, it cannot guarantee the computing ability as a native application on mobile devices, and is not sufficient to improve processing speed. The method proposed in this research overcomes the limitation of resources as a mobile client and guarantees performance by native application software by providing high computing service. It shifts the JavaScript process of a mobile device on to a cloud-based computer server. A performance evaluation experiment revealed the proposed algorithm to be up to 6 times faster in computing speed compared to the existing mobile browser's JavaScript process, and 3 to 6 times faster than Web Worker. In addition, memory usage was also less than the existing technology.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.421-431
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• 2007

Due to the rapid development of wireless communication technology, demands on data services in mobile computing environment are gradually increasing. In mobile computing environments, a mobile host began to use cache to overcome the weak point. Caching at mobile host could reduce the bandwidth consumption and query response time, but mobile host must maintain cache consistency. In this paper, we propose a cache consistency strategy to consider the period of data usage. The server allows an effective broadcasting by classifying data into two groups of periodic and non-periodic. By classifying the data, it prevent from elimination of cache after disconnection of periodic data by using expired time. By storing IR(Invalidation Report) messages, this scheme divides cached data by selection after disconnection. Consequently, we have shown much improvement in total consumption of bandwidth than the conventional scheme.