• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.89-97
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• 2009

The use of database system in application increases day by day. This brought out the DBMS interconnection access problem with rapid increase of the user. To solve these database connection problem, database connection pool has been presented. However, there is much to be desired on user's interconnection access. To improve previous connection pool architecture, we have designed the sub connection pool besides main connection pool in this paper. We defined connection pool broker to manage both main and sub connection pool connection. When main connection pool reached its limitation, connection pool broker transfers a connection from a main connection pool to a sub connection pool. When the interconnection access user increased rapidly, we have proved that the suggested sub pool architecture is more effective on response time by comparing it with other existing DBMS connection pool architectures using simulation.

• Journal of Korea Multimedia Society
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• v.21 no.9
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• pp.1090-1098
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• 2018

MQTT is a lightweight messaging protocol that can be used for low power IoT devices. The MQTT basically uses single MQTT broker to indirectly share message information between publishers and subscribers. This approach has a weakness in regard to traffic overflow, connection fault, security, etc. In this paper, we propose a distributed MQTT broker architecture that solves the problems in single MQTT broker structure. The distributed MQTT broker architecture is expected to support new application services that cannot be supported by a conventional MQTT architecture. We have designed and implemented a distributed MQTT broker architecture based on the RPL protocol that has been widely used for IoT network. The experiment results show that the proposed MQTT broker architecture represents better publishing/subscribing latency and network stability than the conventional MQTT broker architecture.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.3
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• pp.133-141
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• 2018

There are increasing interests on smart home systems. However, most of the existing works focus on the functionality itself. In this paper, we propose an extensible smart home system based on low power networking such as CoAP, 6LoWPAN, and Zigbee. The proposed home IoT system consists of Home APP, Home Server, Home Broker, and Power Devices. Each component of the system is connected by the low-power network technologies aforementioned. As the end device, Power Device senses the current consumption of the attached appliance and controls the power to it. Power Device reports the sensing data to Home Server via Home Broker. The Home Broker enhances the scalability of the system. Home Broker extends the service area and the user's services, and it manages the connection of the underlying devices and processes, and transmits data to Home Server from Power Devices. Through the experimental evaluation, we show that the proposed system achieves the design goals such as extensibility and low power networking.

• KIISE Transactions on Computing Practices
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• v.20 no.12
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• pp.688-693
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• 2014

With the advent of ubiquitous environments, the smart phone has come into wide use and the demand for various content increases. Thus, in order to efficiently utilize limited resources cognitive radio technology is regarded as a possible solution. Besides spectrum sensing or access schemes, the provision of VoIP traffic service for secondary users with limited spectrum resources is a very important issue. In this paper, a resource allocation and control system for VoIP QoS provision in cognitive radio networks is proposed. Firstly, as the system model, the time structure of the network is addressed and, according to the structure, a bandwidth broker is proposed. In addition, based on available bandwidth estimated by the bandwidth broker, a connection admission control for secondary users is developed. It is demonstrated that the provision of VoIP QoS is greatly affected by channel utilization, the number of channels, and the length of timeslot.

• Proceedings of the Korean Society of Computer Information Conference
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• 2008.06a
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• pp.125-130
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• 2008

어플리케이션의 데이터베이스 시스템 사용이 증가하면서, 사용자 급증에 따른 데이터베이스 시스템에 동시접속 하는 커넥션 처리 방법에 있어 중요성이 부각되고 있다. 이러한 데이터베이스의 커넥션을 효과적으로 처리하기 위해 데이터베이스 커넥션 풀이 도입되었으나, 동시접속이 증가하는 형태에 따른 커넥션 처리는 미비한 실정이다. 이 논문에서는 기존의 커넥션 아키텍처를 개선하여 주 커넥션 풀과 보조 커넥션 풀, 두 커넥션 풀의 연결을 할당하기 위한 커넥션 브로커 관계에 있어 새로운 아키텍처를 정의하였고, 실험을 통하여 기존 데이터베이스 커넥션 풀 구조와 비교해서 100% 가량 성능이 향상된 결과를 제시하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06d
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• pp.20-23
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• 2011

하나의 물리 머신만으로 복수개의 가상 머신을 지원할 수 있는 가상화 기술[5,6]이 발달함에 따라, 기업에서는 비용 절감을 위해 가상 데스크탑 기술 도입이 많이 이루어지고 있다. 또한, 일반 사용자들을 위한 가상 데스크탑 기반의 클라우드 서비스 역시 많이 소개되고 있는데, 이러한 가상 데스크탑의 효과적인 사용을 위해서는 원격 접속 기술이 필수적이지만, 이는 키보드, 마우스 및 디스플레이가 감추어져 있는 PC와 같은 정형적인 컴퓨터 환경에서만 접속이 가능하다[3,4]. 본 논문에서는 스마트폰을 이용하여, 사용자 주변에서 원격 컴퓨팅 장치로 사용할 수 있는 LCD TV, 키보드 등의 레거시 디바이스를 검색하고 해당 디바이스를 원격지에 있는 가상 데스크탑과 연계시켜[1,2] 사용자 주변의 디바이스를 통해 원격 가상 데스크탑 제어를 연계 할 수 있는 중계 소프트웨어에 대한 설계 및 구현 내용을 기술하고 있다.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.6
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• pp.771-781
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• 1999

오늘날의 컴퓨팅 환경은 통신 네트워크의 복잡성과 다양한 멀티미디어 서비스 처리를 위해 객체지향 기술을 분산 시스템에 도입하고 통신망을 소프트웨어 계층적 모델로 구조화한 개방형 정보 통신망 구조 연구가 활발히 진행되고 있다. 본 논문은 분산환경에서 멀티미디어 스트림 데이타를 전송하기 위한 아키텍쳐에 관한 모델의 설계 및 구현에 관한 것으로 분산 환경에서 멀티미디어 스트림 데이타를 효율적으로 전송할 수 있는 구조를 제시하고 있다. 설계한 구조는 Point-to-Point와 멀티캐스트를 지원하며 컴퓨터 통신망에서 멀티캐스트 연결을 효율적으로 관리하고 추후 기능 확장 및 기능 변경이 용이하도록 모듈화하고 유연성을 가지는 연결 관리 구조를 설계하고 구현하였다. 신호기능은 CORBA(Common Object Request Broker Architecture)의 ORB를 이용하여 실현하였으며, 데이타 전송 기능은 TCP/IP연결을 이용하였다. 이렇게 신호처리 부분과 데이타 전송 부분을 독립적으로 만들어서 하부망 기술에 독립적인 연결 관리 구조를 채택하고 있으므로 향후 다른 환경에서도 신호처리 부분을 그대로 적용할 수 있다. 분산 객체 개념을 적용하여 연결 관리 기능을 분산 객체화 하였으며 각 분산 객체간 인터페이스를 OMG(Object Management Group) IDL(Interface Definition Language)로 정의함으로써 유연성을 갖도록 하였다.AbstractThis paper proposes communication service architecture to support dynamic communication configuration and multiple connection management which are required to handle a variety of multimedia multicast application. Our communication service architecture was designed to fulfil the objectives as the following:- To build a common networking system for various multimedia multicast services- To build a platform for rapid service development and provisioning- To provide service networking independent on transport network technologiesWe implemented communication service architecture based on Common Object Request Broker Architecture (CORBA) for multimedia multicast applications. Our communication service architecture is distributed and object-oriented for extensibility and easy modification. The interfaces between the distributed objects are specified in (Object Management Group) OMGs Interface Definition Language.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.744-747
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• 2017

The Internet of things (IoT) needs to be an event-driven approach for efficient real time response and processing. An IoT gateway is sometimes employed to provide the connection and translation between devices and the cloud. Storing data in the local database, and then forwarding it on the cloud is a task to be relegated to a gateway device In this paper, we propose the design of the IoT gateway with Fog computing for storing data from sensors into a local database. In the procedure of designing storing tasks, we propose to use the interfacing software known as Ardulink MQTT bridge. MQTT is a protocol for sensors to publish data to the clients. When it comes to needing historical data, MQTT connector can push MQTT data into SQL database. We write an MQTT client and based on the message topic insert the values into a SQL Database The design of IoT gateway with Fog computing adds value because it provides processing of the data across multiple devices before it sends to the cloud.

• Journal of IKEEE
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• v.25 no.2
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• pp.291-301
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• 2021

OPC UA at the control and field level does not provide enough performance to replace the field bus. The OPC Foundation aims for a real-time and connection-less mechanism, and has added the OPC UA publish-subscribe model, a new specification that supports broker functions such as MQTT and AMQP, as the OPC UA Part 14 standard. This paper is about a gateway for interoperability between OPC UA publisher with the addition of OPC UA Part14 standard and DDS subscribers. Raspberry Pi 4 is used for the gateway proposed in this paper, and OpenDDS, an open source, is used for DDS. OPC UA publish-subscribe module used A-Open62541 publish-subscribe module, which additionally implements functions not provided by the corresponding source based on Open62541 publish-subscribe open source.