• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.427-429
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• 2006

데이터 그리드는 분산 데이터베이스 환경에서 상호간 데이터의 공유 및 교환을 통하여 분산 데이터를 효율적으로 사용하기 위한 기술이다. 최근에는 레거시 시스템간의 협업을 하기 위해 상호 연결의 필요성이 강조되고 있으며 많은 연구가 진행되고 있다. 독립주인 레거시 시스템을 상호 연결하기 위해서는 노드간의 회선 점유율이 증가하고, 데이터의 이질적인 문제가 발생한다. 이러한 문제점을 해결하기 위해 본 논문에서는 XMDR 기반의 데이터 그리드 시스템을 제안한다. 본 논문의 데이터 그리드 미들웨어는 ISO/IEC11179에서 제안한 정보 공유 및 교환을 위한 표준인 MDR과 정보의 효율적인 이용을 위한 온톨로지를 포함하여 확장한 개념인 XMDR(eXtended Metadata Registry)에 기반을 두었으며 분산 플랫폼으로부터 독립적이고 자유로운 이동성을 가지고 있는 이동 에이전트 기술을 사용하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.4
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• pp.334-342
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• 2014

Military communications for future warfare have limited resources but highly requirements. MANET has a lot of advantages for future military network due to easily deploying without infrastructure and supporting dynamic topology in restricted environments. But, one of the biggest issues for MANET is difficulty of transmitting data due to link failure in dynamic topology. Content Centric Networking is a future Internet paradigm which solves various IP network problem. In this paper, we propose a future military communication routing scheme using CCN in military tactical MANET. Simulation results show our scheme gets lower control message overhead and faster data downloads as number of node increases and mobile speed increases than other two schemes.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.26-33
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• 2011

In ubiquitous environments that numerous mobile objects exist, the location-based services have risen as an important application field. For efficient location-based services, various techniques with broadcast schemes have been studied. However, they were mainly concerned with the implementation of a broadcast index and did not consider techniques for reducing the size of the entire broadcast data. Therefore, this paper proposes a data distribution broadcast scheme based on sensor networks that considers the mobile patterns of an object in road network environments. In this paper we also propose a road network based sensor clustering technique for the efficiency of the proposed distributed broadcast scheme. In order to show the superiority of the proposed scheme, we compare it with the existing broadcast scheme in various environments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.15-23
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• 2013

In this paper, we propose a session management and control architecture for N-Screen services, which enable users to change devices and transfer contents among user's devices during service by session transfer and split. In N-Screen services, users may have multiple devices with different attribute such as screen resolution, CPU capability and access network interfaces. Also, since users may change devices during service, or one user may use multiple stream, N-Screen services need to enable the user to share and transfer contents across N-Screen devices. We introduce the management and control servers to provide session split over user multiple devices and session continuity while changing device. Furthermore, the proposed architecture provides the device capabilities aware session continuity. In addition, the proposed scheme minimizes the session transfer delay and content server processing load. We present results that show the effectiveness and usefulness of proposed architecture.

• The Journal of Korean Institute of Next Generation Computing
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• v.13 no.5
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• pp.51-70
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• 2017

The reliability of broadcasting over vehicular ad hoc networks (VANETs) is one of the most critical factors for driving safety applications. There exists limitations to improve the reliability of broadcast transmissions in saturated VANETs where previous proposals in literature tackle the problem by heuristically adapting the size of the contention window (CW). This paper considers improving the reliability by proposing a new probability model based on the counting methods of permutations and combinations, which counts all the possible cases of broadcast failures in a single-hop broadcast transmission for a given CW. From the model, we calculate the best CW size given the number of contention nodes, which significantly improves the reliability and satisfying the timely dissemination of emergency broadcasting messages. Through extensive VANET simulations with varying densities, we show that our model maintains near 100 percent success rate for single-hop broadcast as well as multi-hop broadcast (e.g. 40 hops) and achieves minimal broadcast delay.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.48-59
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• 2009

Next generation mobile communication system will have various access networks and provide seamless multimedia data service to mobile nodes. The WiNGS system, one of these access network, has superior RAT(Radio Access Technology) and network connectivity other than previous ones. In this paper, we propose link-layer SR-ARQ between mobile node and WAGW to solve packet re-ordering problem during handover. In the proposed scheme, we apply the adaptive timer at the SR-ARQ sender to reduce unnecessary packet retransmission during handoff and delayed NAK algorithm at the SR-ARQ receiver for delaying NAK response due to temporary out-of-sequenced frames. We evaluate the performance of the proposed scheme by implementing the new SR-ARQ protocol at the link-layer using ns-2 simulator, and show the handover performance is improved greatly by preventing unnecessary retransmission.

• Journal of Digital Contents Society
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• v.14 no.1
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• pp.89-95
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• 2013

Many peer-to-peer (p2p) systems have been studied in distributed, ubiquitous computing environments. Distributed hash table (DHT)-based p2p systems can improve load-balancing even though locality utilization and user mobility are not guaranteed. We propose a mobile locality-based hierarchical p2p overlay network (MLH-Net) to address locality problems without any other services. MLH-Net utilizes mobility features in a mobile environment. MLH-Net is constructed as two layers, an upper layer formed with super-nodes and a lower layer formed with normal-nodes. The simulation results demonstrate that MLH-Net can decrease discovery routing hops by 13% compared with JXTA and 69% compared with Chord. It can decrease the discovery routing distance by 17% compared with JXTA and 83% compared with Chord depending on the environment.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1000-1003
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• 2010

VANET은 차량 이동 간 안전성 증가와 관련 응용정보를 처리하기 위해 고안된 ad-hoc 통신기반의 무선 네트워크 기술이다. VANET 환경을 이용하면 도로 교통 통제, 날씨 정보, 인터넷 등 다양한 서비스가 가능하다. VANET 환경을 위해서는 효과적인 노드간의 라우팅 프로토콜 기법이 필요하다. 본 논문에서는 VANET상에서 각 차량의 정보를 이용하여 차량 간 안정적인 통신을 위한 그룹화 라우팅 기법을 제안한다. 제안된 기법을 통해 그룹화를 통한 라우팅 기법이 VANET 환경에 더 효과적임을 알 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2435-2441
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• 2010

A global healthcare system based on M2M technology is proposed to support a good mobility, flexibility and scalability to the patients in 6LoWPAN. Sensor nodes integrated with wearable sensors are linked to gateway with IEEE 802.15.4 protocol and 6LoWPAN protocol for data acquisition and transmission purpose via external network. In the server, heart rate variability signals are obtained by signal processing and used for time and frequency domain performance analysis to evaluate the patient's health status. Our approach for global healthcare system with non-invasive and continuous IP-based communication is managed to process large amount of biomedical signals in the large scale of service range accurately.

• Journal of Internet Computing and Services
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• v.10 no.5
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• pp.13-26
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• 2009

Wireless Sensor Networks (WSNs) is one of the key technologies that make it possible to provide u-service in a ubiquitous society, however, it has disadvantages such as difficulty of managing sensor nodes and weaknesses of stability or mobility in large-scale WSNs. In order to solve these problems, 6LoWPAN that integrates with WSNs and IP networks has been studied widely. In this paper, we propose a Location Tracking Service Based on Google Map (LTSGM) system using 6LoWPAN. Since LTSGM system provides visual location information of sensor nodes through Google Map, it is possible to makes it easier than ever to manage sensor nodes in large-scale WSNs. Moreover, LTSGM can be used for various services such as applications for disaster or crime because it can trace the location of mobile nodes. Implementation of LTSGM system will be a test platform for 6LoWPAN.