• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.402-407
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• 2005

The PLL synthesizer is used in communication system until now because it have several merits, such as broad bandwidth, high accuracy and stability of frequency But it is difficult to use in the third generation mobile communication systems that need frequency hopping at a high speed because of its long frequency hopping time. In this paper, we designed the frequency synthesizer that generate frequencies randomly at a high speed using the DDS technology.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06b
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• pp.303-307
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• 2010

DDS(Data Distribution Service)는 통신 환경의 확장성과 데이터의 신뢰성을 보장하는 통신 미들웨어이다. DDS에 대한 표준과 미들웨어들은 많은 연구가 이루어 지고 있으나, DDS 미들웨어상에서 동작하는 DDS 응용의 운용 기술에 대한 연구는 아직 미비한 실정이다. 본 논문에서는 DDS 미들웨어 상에서 동작하는 각 DDS 응용들이 사용하는 데이터 구조를 모니터링하고, 사용자의 요구에 따라 DDS 응용을 검색하고 설치 및 제어가 가능한 디렉토리 서비스를 제안하였으며 프로토타입 구현을 통해 제안된 기술이 실현 가능함을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1229-1234
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• 2012

In this paper, we analyze the problems that the DDS middleware, which is a standard data-centric communication interface, uses the fixed packet transmission method by the pre-defined protocol for exchanging data packets. The packet transmission method selected in a fixed manner cannot handle appropriately the increasing of resource overhead in an environment where the load of the DDS network changes dynamically. If the load on the node and network exceeds the threshold, the performance of the packet transmission may be degraded rapidly. This results in a failure of ensuring the real-time characteristic of DDS middleware. To solve this problem, we propose the scheme of the adaptive packet transmission for adjusting the transmission method in real-time based on the overhead on the DDS network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.205-208
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• 2011

In recent years, the user interest has increased for DDS (Data Distribution Service) which is a data centric middleware based on publish-subscribe communication as the demands for real-time data exchange in distributed systems have been growing rapidly. To reflect these needs, many vendors and research groups provide their DDS middleware. However, there has been a problem with interoperability between DDS middlewares because of a lack of common communication rules such as the message exchange and the discovery manner. For this reason, OMG defines RTPS (Real-Time Publish-Subscribe) specification which is the standard network protocol used to exchange data between different implementations of DDS. In this paper, we analyze and design the SDP (Simple Discovery Protocol) of RTPS which enable DDS middleware to provide interoperable discovery mechanism.

• The Journal of Korean Institute of Next Generation Computing
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• v.14 no.6
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• pp.75-86
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• 2018

The DDS (Data Distribution Service) specification defines a discovery method for finding participants and endpoints in a DDS network. The standard discovery mechanism uses the multicast protocol and finds all the endpoints in the network. Because of using multicasting, discovery may fail in a network with different segments. Other problems include that memory space wastes due to storing information of all the endpoints. The Topic Name Service (TNS) solves these problems by unicasting only the endpoints, which are required for communication. However, an extra delay time is inevitable in components of TNS, i.e, a front-end server, topic name servers, and a terminal server. In this paper, we analyze the performance of TNS. Delay times in the servers of TNS and time required to receive endpoint information are measured. Time to finish discovery and number of receiving endpoints compare with the standard discovery method.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.125-129
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• 1986

DDS network was implemented by utilizing the digital transmission in PSIN and finished field trial successfully for the first time in our country by DTC. Concept of DOS, how to implement, detail description of each section, comparison of DOS vs, analog data transmission system and result of field trial are presented.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.579-581
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• 2017

OMG(Object Management Group)의 DDS(Data Distribution Service)는 Publish/Subscribe기반 통신 미들웨어로 DDS Participant Discovery를 사용하여 각 Topic에 대한 Participant 정보를 자동으로 교환하여 사용자에게 편의성을 제공하며 분산 환경에 적합한 통신 환경을 제공한다. 본 논문에서는 기존 DDS의 원격 도메인간의 Participant Discovery 문제 해결을 위해 SDN 기반 구조를 제안한다. 제안하는 구조는 DDS 미들웨어에 SDN Controller로 도메인 정보를 전달할 기능(function)을 추가하고 SDN controller상에 Participant Discovery를 위해 네트워크 설정을 수행할 컴포넌트들을 추가한다. 이 구조는 원격 도메인간 PDP Message가 전달되지 않는 문제를 해결하며 실제 네트워크에 전달되는 Participant Discovery 메시지 수를 감소시켜 DDS Discovery 기능을 효율적으로 확장시킨다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.728-731
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• 2012

최근 분산 임베디드 시스템에서 실시간 데이터 교환에 대한 요구가 증가하면서 발간/구독(Publish/Subscribe) 기반의 데이터 중심 통신 미들웨어인 DDS(Data Distribution Service)에 대한 활용 분야가 증가하고 있다. 국방 분야의 시스템과 같은 고신뢰성을 요구하는 환경에서는 시스템 개발에 앞서, DDS 통신에 동적으로 참여하게 하는 디스커버리 과정의 안정적인 성능 검증을 요구한다. 성능 검증 및 신뢰성 있는 시스템 개발을 위해 실제 시스템과 유사한 환경에서 DDS의 디스커버리 사전시험(Prototype)을 수행하는 데, 이 때 많은 시간과 비용을 소요하게 된다. 본 논문에서는 DDS의 표준 프로토콜인 RTPS(Real-Time Publish-Subscribe)에서 필수로 요구하는 SDP(Simple Discovery Protocol)를 이용하여 디스커버리 시간을 추정할 수 있는 계산식을 제안한다. 계산식은 참여자(Participant) 수를 이용한 연결 쌍(pair)의 수식과 단말개체(Endpoints) 수를 이용한 가중치(weight) 수식을 이용하며, 실제 상용 DDS 미들웨어를 이용하여 유형별로 DDS 디스커버리 시험을 수행한 결과와 비교하여 계산식을 실제로 사용할 수 있음을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.11B
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• pp.1732-1737
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• 2010

Currently, one of the main purposes of the military using Unmanned Air System (VAS) is to perform surveillance and reconnaissance of hostile enemy. To carry out their mission, Unmanned aerial vechicle (UAV) transmits video images to ground control station using ISR devices installed on the UAV. After receiving the images, the ground control station distribute them to various type of users. At this case, it is important to keep QoS. This paper presents data delivery and QoS managements using DDS for DDS for UAV video images. The experiment result, based on H.264 and JPEG2000, shows that DDS standard is able to be applied to video image transmission for UAS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.739-746
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• 2016

The real-time railway safety monitoring and control system is for prevention of safety accidents, and this system adopts DDS (Data Distribution Service) standard based data transmission method to support integrated management of data from existing on-site safety detection devices. In this paper, we introduce the design of DDS-based data specification from on-site signal equipment on the conventional railway. For this, we (1) design UML data model of KRS SG 0062 standard which defines existing data specification, (2) define DDS Topics for DDS transmission and map KRS model to DDS Topic model, (3) suggest data transformation rules and (4) design network control QoS polices. In addition, we analysis actual on-site log data and validate our data specification design. DDS-based data transmission enables data compatibility among on-site devices and the real-time railway safety monitoring and control system, and allows efficient network management for a large amount of data transfer.