• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1575-1578
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• 2002

단말기의 컴퓨팅 능력과 이동 통신 기술이 발달함에 따라, 무선 이동망에서도 현재의 데스크탑에 버금가는 인터넷 컴퓨팅이 가능해 지고 있다. 브로드캐스팅(broadcasting)은 비대칭 통신 환경에서 정보를 효과적으로 전달하는 방법이다. 다수의 사용자가 요구하는 동일한 종류의 실시간 데이타를 전송할 경우, 무선 환경에서는 브로드캐스트 기법이 효과적이다. 그러나 유료 정보를 무선망에 브로드캐스트 할 경우 허가되지 않은 사용자들도 해당 정보를 이용할 수 있는 문제가 발생한다. 그러므로 이 경우 기존의 브로드캐스트 기법을 사용하는 대신, 1:1 전송 방식 또는 멀티캐스트 방식을 사용해야 한다. 그러나 사용자의 수가 많을 경우와 전송할 데이터의 크기가 커질 경우 기존의 방식들은 통신 오버헤드를 증가시킬 수 있다. 그러므로 사용자가 많고 전송할 데이터가 큰 경우 효율적인 통신을 위해서는 특정 사용자들에게 선별적 전송이 가능한 브로드캐스트 기법이 필요하다. 본 논문에서는 공개키 암호화 기술을 사용하여 정보를 허가된 사용자에게만 전송하는 브로드캐스트 기법을 제안하고 그 성능을 분석한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.1132-1135
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• 2011

최근에 무선 통신 기술의 발달과 함께 스마트폰의 보급 확대로 언제 어디서든지 질환관리가 가능한 착용형 센서 기반 질환관리 서비스가 활발하게 개발되고 있다. 논문에서는 웹 클라이언트와 스마트폰 클라이언트의 두 가지 이용 유형을 효과적으로 통합하는 혈압관리 서비스 시스템을 MVC 구조에 기반하여 개발한다. 논문 방법은 서비스의 이용 범위 확대, 유용 가능성, 연속성의 이점을 제공한다.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.22-30
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• 2023

The portable mobile devices with high performance and high speed 5G network activate and explode the demands for ubiquitous information services that remove the limitations of time for the communication and places to request for the information. NN (Nearest Neighbor) search is one of the most important types of queries to be processed efficiently in the information services. Various indexes have been proposed to support efficient NN search in the wireless broadcast system. The indexes adopting Hilbert curve, grid partition or Voronoi diagram enable the clients to search for NN quickly in the wireless broadcast channel. It is necessary that an efficient means to evaluate the performances of various indexes. In this paper, we propose an open framework that can adopt a variety of indexing schemes and evaluate and compare the performances of them. The proposed framework is organized with open and flexible structure that can adopt hybrid indexing schemes extensible to Voronoi diagram as well as simple indexing schemes. With the implemented framework, we demonstrate the efficiency and scalability and flexibility of the proposed framework by evaluating various indexing schemes for NN query.

• Journal of KIISE:Software and Applications
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• v.26 no.9
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• pp.1085-1094
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• 1999

이동 분산 환경에서는 무선 데이타 전송 기법을 통하여 사용자들에게 다양한 정보들을 전달하게 된다. 본 논문은 균등 무선 데이타 방송 환경에서, 빠른 시간에 방송데이타를 접근할 수 있는 방법에 대하여 기술한다. 이를 위하여 무선 방송 데이타의 스케쥴링 문제를 정의하고, 어떤 질의가 접근하는 데이타들의 응집 정도를 나타내는 `질의 거리(Query Distance: QD)'라는 측정 기준을 제시한다. 제안한 질의 거리를 사용하여 각 질의의 우선 순위에 따라 해당 질의가 접근하는 데이타 집합을 방송 스케쥴에 추가하면서 스케쥴을 구성하는 데이타 스케쥴링 기법을 제시한다. 데이타 집합의 스케쥴 구성 과정에서 우선 순위가 높은 질의의 질의 거리를 최소화하면서 낮은 우선 순위 질의들의 질의 거리를 줄이는 스케쥴 확장 규칙들을 사용한다. 예를 이용하여 제안하는 방법에 대하여 설명한 후, 실험을 통해 제안한 방법의 성능을 평가한다.Abstract In mobile distributed systems the data on the air can be accessed by a lot of clients. This paper describes the way clients access the broadcast data in short latency in uniform wireless broadcasting environment. We define the problem of wireless data scheduling and propose a measure, named Query Distance(QD), which represents the coherence degree of data set accessed by a query. By using the measure, we give a data scheduling method that constructs the broadcast schedule by appending each query's data set in greedy way. When constructing the schedule, we use schedule expansion rules that reduce the QD's of lower-frequency queries while minimizing the QD's of the higher-frequency ones. With the use of examples we illustrate the mechanism of the proposed method and we test the performance of our method.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.113-119
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• 2017

The Rich Communication Service(RCS) is a next generation mobile messaging service. Since it has been developed and managed by a wireless service provider, 3rd party application developers cannot utilize the RCS features in their apps. A few studies have been proposed to solve this problem, even though they were not viable level of deployment. This paper presents a Web-based Rich Communication Service Software Framework(WebRSF) to help the 3rd party application developers adopt RCS features easily. WebRSF converts complicated RCS protocols to simple web-based protocols for providing the RCS 1-to-1 chat service to the 3rd parties. Communication protocols between WebRSF and its clients are defined in this paper. Also, a network configuration diagram and a message flow diagram are defined. Finally, performance evaluation between the WebRSF client and the RCS client are performed to simulate the load on clients' devices. It shows that the WebRSF client has 17% less loads than the RCS client while initiating sessions, and has 25% more loads after initiating sessions.

• Journal of KIISE:Databases
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• v.36 no.1
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• pp.30-43
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• 2009

Broadcast in the wireless environment has drawn much attention because it is capable of sending data to clients regardless of the number of clients. Most previous researches have aimed at obtaining an independent data item in a minimum time. But, they have not been researched on simultaneously receiving dependent data items in a query. In addition, these papers have only researched allocation problem that have not been came out data items in a query in same time and different channels. The access probability of each data item based on query request probability have not been reflected. This paper proposes a new method of allocating data items and simultaneously minimizing average response time required in receiving all the dependent data items in a query. Our performance analysis shows that our proposed method gives better average response time over the existing methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2119-2124
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• 2016

The Internet of things (IoT) needs to be an event-driven approach for efficient related time response and processing. The growth of mobile devices in Internet of Things (IoT) leads to a number of intelligent buildings related IoT applications. For instance, home automation controlling system uses client system such web apps on smartphone or web service to access the home server by sending control commands. The gateway based RESTful technology responsible for handling clients'requests attests an internet latency in case a large number of clients' requests submit toward the gateway increases. In this paper, we propose the design tasks of the IoT gateway for handling concurrency events. The gateway based event-driven architecture is designed for building IoT gateway using node.js on one side and communication protocol based message-oriented middleware known as XMPP to handle communications of intelligent building control devices connected to the gateway through a centralized hub.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.99-107
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• 2008

Recently route guiding system using GPS is spread widely. In the parking management system of complex mall, RFID is mainly used to control status of parking lots. However, in a case that a vehicle only with RFID tag enters into small market-populated district with service of parking lots, there is no parking route guiding system optimized with information of real tine status of parking lots and the system only with GPS can't provide a function of using real time status of parking lots. This paper proposes a location recognizing method of RFID tag object for parking control system to integrated several parking lots in the business district and database-linked route guiding system optimized for parking. The proposed location recognizing method makes the search of optimized parking route possible by abstracting decoding order of tag and antenna number and recognizing direction of tag linked with database. Ihe implemented system that is composed of RFID tag, reader, middleware, server, parking lot clients and mobile clients shows that the proposed method works well and it will be useful for integrated parking control system.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.9
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• pp.327-336
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• 2015

Mobile game servers usually execute frequent dynamic memory allocation for generating the buffers that deal with clients requests. It causes to deteriorate the performance of game servers since it increases system workload and memory fragmentation. In this paper, we propose fixed-sized memory pool management method. Memory pool for the proposed method has a sequential memory structure based on circular linked list data structure. It solves memory fragmentation problem and saves time for searching the memory blocks which are required for memory allocation and deallocation. We showed the efficiency of the proposed method by evaluating the performance of dynamic memory allocation, through the proposed method and the memory pool management method based on boost open source library.

• Journal of the Korea Computer Graphics Society
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• v.21 no.3
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• pp.17-26
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• 2015

In this paper, we explain a volume rendering system for client-server environment. A single GPU-equipped PC works as a server which is based on the ideas that only a few concurrent users use a volume rendering system in a small hospital. As the clients, we used Android mobile devices such as smart phones. User events are transformed to rendering requests by the client application. When the server receives a rendering request, it renders the volume using the GPU. The rendered image is compressed to JPEG or PNG format so that we can save network bandwidth and reduce transfer time. In addition, we perform an event pruning method while a user is dragging the touch to enhance latency. The server compensates the pruning by interpolating the touch positions. As the result, real-time volume rendering is possible for 5 concurrent users on single GPU-equipped commodity hardware.