• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.232-234
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• 2002

무선 통신 및 컴퓨터 기술의 발달은 사용자로 하여금 이동 중에도 휴대용 컴퓨터를 소지하고 무선 통신을 통해 다양한 비즈니스 트랜잭션을 수행할 수 있는 모바일 오피스(mobile of Hee)환경을 제공하고 있다. 그러나 무선 통신과 휴대용 컴퓨터의 고유한 특성으로 인해 이동 비즈니스 트랜잭션 처리에 유선망에서 사용되는 트랜잭션 처리 모델을 그대로 적용할 경우 트랜잭션 응답시간이 길어지고 데이터 관리가 복잡해지며, 통신 요금이 증가하는 등의 문제점이 발생한다. 본 연구에서는 고가의 무선통신 비용 및 이동 컴퓨터의 배터리 소모를 절감하기 위해 접속단절을 효과적으로 이용하여 회사와 이동 세일즈 사원들 간의 효율적인 비즈니스 트랜잭션 처리 시스템 구축을 위한 트랜잭션 처리 모델을 제안한다.

• Journal of KIISE:Databases
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• v.33 no.1
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• pp.69-85
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• 2006

Broadcast has been often used to disseminate the frequently requested data efficiently to a large volume of mobile clients over a single or multiple channels. Conventional concurrency control protocols for mobile transactions are not suitable for the wireless broadcast environments due to the limited bandwidth of the up-link communication channel. In wireless broadcast environments, the server often broadcast different data items with different frequency to incorporate the data access patterns of mobile transactions. The previously proposed concurrency control protocols for mobile transactions in wireless broadcast environments are focused on the mobile transactions with uniform data access patterns. However, these protocols perform poorly when the data access pattern of update mobile transaction are not uniform but skewed. The update mobile transactions with skewed data access patterns will be frequently aborted and restarted due 4o the update conflict of the same data items with a high access frequency. In this paper, we propose an energy-efficient concurrence control protocol for mobile transactions with skewed data access as well as uniform data access patterns. Our protocol use a random back-off technique to avoid the frequent abort and restart of update mobile transactions. We present in-depth experimental analysis of our method by comparing it with existing concurrency control protocols. Our performance analysis show that it significantly decrease the average response time, the amount of upstream and downstream bandwidth usage over existing protocols.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.257-271
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• 2008

Wireless broadcast environments has character that a number of mobile client can receive data streaming from central server no matter how they are so many. Because it is asymmetric bandwidth in that uplink and downlink bandwidth are different. This advantage helps wireless broadcast environments is used in many applications. These applications work almost read operation and need control concurrency using transaction unit. Previous concurrency control scheme in single channel is not adapted in multi channel environments because consistency of data are broken when a mobile client tunes in a broadcast cycle in a channel and then move into another channel and listen to different broadcast cycle with already accessed broadcast cycle. In this paper, we propose concurrency control for read-only mobile transactions in multiple wireless broadcast channel. First of all, we adapt index and data dedicated channel and propose LBCPC(Longest Broadcast Cycle Per Channel) as new unit of consistency. In index dedicated channel, it is repeatedly broadcasted data in same BCPC(Broadcast Cycle Per Channel) until LBCPC. And mobile transaction executes validation using control information every LBCPC. As a result, consistency of data is kept and average response time is shorter than one in single channel because waiting time for restart reduces. And as control information is broadcasted more frequently than in single channel, it is guaranteed currency about data accessed by transaction. Finally, according to the simulation result, we verify performance of our scheme in multi channel as comparing average response time with single channel.

• Journal of KIISE:Databases
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• v.30 no.4
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• pp.397-407
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• 2003

Transactions of updating spatial dta with mobile clients are log transactions because a user disconnected from a server surveys real features and updates them. In this environment, it is appropriate to exploit the optimistic approach based on the validation test in order to control the concurrency of transactions. On the contrary, the pessimistic concurrency control scheme makes transactions wait for a long time due to the lock. In this paper, we propose the surrogate transaction model and implement its manager for the S-S-M(Server-Surrogate PC-Mobile Client) structure which is appropriate for updating spatial data in mobile environments. In the S-S-M structure, the mobile client communicates with the server by the surrogate PC. We extend the validation condition in consideration of spatial relationships between spatial objects in this model. We also present the commit protocol where the user of a surrogate PC adjusts objects of the conflicted surrogate transaction to minimize costs for the abortion of the transaction.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.217-219
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• 2005

최근 들어 무선 인터넷 및 모바일 기술이 급속한 발달을 이루면서 이동 객체의 위치에 기반 한 많은 서비스들이 개발되고 있다. 이 서비스에 사용되는 않은 어플리케이션들은 비교적 용량이 큰 공간 정보를 사용하여 최근에는 기존 디스크 기반 데이터베이스 관리 시스템이 제공할 수 있는 처리 속도보다 더욱 빠른 트랜잭션 처리를 요구하고 있다. 따라서 공간 데이터와 같은 대용량 데이터의 효율적인 처리와 폭주 하는 여러 사용자들에게 빠른 응답시간을 제공하여 주는 공간 DBMS가 요구되고 있다. 기존 디스크 기반의 공간 DBMS는 공간데이터와 같은 대용량의 데이터 관리가 가능하지만, 빠른 응답속도를 요구하는 여러 어플리케이션을 지원하기에는 무리가 있다. 반면에 메인 메모리 기반의 공간 DBMS는 불필요한 디스크 I/O를 없앰으로써 더욱 빠른 트랜잭션 처리를 지원하지만, 메인 메모리의 저장 한계로 대용량 처리에는 한계가 있다. 이러한 이유로 디스크 공간 DBMS의 장점과 메인 메모리 공간 DBMS의 장점으로 이루어진 다중레벨 공간 DBMS를 제안한다. 다중레벨 공간 DBMS는 디스크 기반의 공간 DBMS인 GMS시스템에 메인 메모리 데이터베이스와 그와 관련된 여러 컴포넌트들을 추가하여 개발 하였다. 제안된 시스템은 디스크 데이터베이스 기반의 대용량 데이터의 효율적인 관리와 메모리 데이터베이스 기반의 빠른 트랜잭션 처리를 보장한다.

• Information Systems Review
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• v.10 no.2
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• pp.309-327
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• 2008

This research is a byproduct of a project initiated by a major airport in Korea. The airport aimed to enhance airside safety and weighed a few IT options that may strengthen its current safety practices. In order to satisfy requirements unique to the airport and to inherit existing legacy systems, a PCS-based mobile database system was proposed. We first discuss technical aspects of the system as well as design issues in mobile systems before we compare two specific alternatives for transactional service handoff. A simulation study comparing two types of coordination follows before we present a scheme that manages transaction processing and locating service in mobile environments. Finally, we discuss the limitations of the scheme from the perspectives of the airport in question along with other research issues.

• 한국공간정보시스템학회:학술대회논문집
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• 2003.11a
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• pp.84-90
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• 2003

최근 이동 컴퓨팅 기술이 급속도로 발전하면서 이동 객체의 위치정보를 활용한 위치 찾기 서비스, 교통 정보 서비스, 긴급 구조 서비스, 모바일 광고 서비스와 같은 위치 기반 서비스가 부각되고 있다. 이와 같은 다양한 서비스를 제공하기 위해서는 이동 객체의 위치정보를 신속하게 저장, 검색, 갱신할 수 있는 이동 객체 데이타베이스 시스템이 필수적으로 요구된다. 그러나, 기존의 데이타베이스 시스템을 사용할 경우에는 저장 공간을 많이 차지게 되고, 불필요한 트랜잭션 연산으로 인하여 대용량의 위치 데이타 관리에 큰 오버헤드가 발생한다는 문제가 있다. 그러므로, 이동 객체의 위치 데이타를 저장하고 관리하기 위하여 화일 기반의 저장 시스템을 사용하는 것이 보다 더 효율적이다. 이에 본 논문에서는 대용량의 위치 데이타를 효과적으로 저장 및 검색할 수 있는 화일 기반 이동 객체 저장 컴포넌트를 설계하고 구현하였다. 화일 기반 이동 객체 저장 컴포넌트는 다중 연결 관리자, 단순 질의 처리기, 메타데이타 관리자, 데이타 화일 관리자, 인덱스 화일 관리자, 로그 관리자, 관리툴로 구성된다.

• Spatial Information Research
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• v.19 no.3
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• pp.43-52
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• 2011

Recently, interest in location-based service (LBS) which utilizes a DBMS in mobile system environment has been increasing, and it is expected to overcome the existing file-based system's limitation in advanced in-vehicle system by utilizing DBMS's advantages such as efficient storage, transaction management, modelling and spatial queries etc. In particular, the road network data corresponds to the most essential domain in a route planning system, which needs efficient management and maintenance. Accordingly, this study aims to develop an efficient graph-based geodata model for topological network data and to support dynamic path computation algorithm based on heuristic approach in mobile LBS system. To achieve this goal, we design a data model for supporting the hierarchy of network, and implement a path planning system to evaluate its performance in mobile LBS system. Last but not least, we find out that the designed path computation algorithm with hierarchical graph model reduced the number of nodes used for finding and improved the efficiency of memory.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.6
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• pp.63-69
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• 2009

The decentralized and open characteristic of the internet, along with the mobility and portability of mobile communication, and the interactivity of the internet and mobile communications all have been grafted to enable the creation of wireless internet in our lives, bringing about a lot of change. However, existing system management software solutions show limitations in time and space, as well as problems such as uncertain error messages, and also difficulty providing swift assistance or real time emergency support. Therefore, a wireless remote control system has been designed and implemented in this thesis, which is capable of managing and monitoring remote systems using mobile communication devices (Mobile Phone, PDA, Smart Phone, Webpad) for realtime control. The implemented real time wireless remote control system provides remote server management functions, error or event message functions, log record functions, authentication function via mobile devices and system performance evaluation function classified by client transaction.