• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.4
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• pp.295-301
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• 2020

When a spacecraft in deep space falls into an abnormal state, an emergency communication channel between ground and the spacecraft is essential in order to perform analysis to the cause of the anomaly, and to remedy the spacecraft from the distressed state. Because the recovery actions generally comprises of long and complicated sequences of commands, the transmission of the recovery commands may require a reliable and a delay tolerant networking technology based on bundle routing. While the delay tolerant networking protocol becomes a prominent method interfacing ground and space into a internet-like Solar system network because it can address the issues of the severe communication problems in deep space, the communication system on the spacecraft which based on space packet protocol cannot use the delay tolerant networking technology directly. So a community of the consultative committee for space data systems starts a discussion of the first-hop last-hop mechanism to establish a feasible concept and standardization. This paper presents an enhanced concept of the first-hop last-hop by applying it a virtual cislunar communication environment, and we believe this contributes to make a way applicable to an interoperable relay concept of the first hop last hop between the delay tolerant networking and space packet protocol standard.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.1-9
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• 2014

Delay-Tolerant Network (DTN) is an asynchronous networking technology that has been deployed for the networking environment in which steady communication paths are not available, and therefore it stores receiving data in a data storage and forward them only when the communication links are established. DTN can be applied to sensor networks and mobile ad-hoc network (MANET) as well as space communication that supports data transmissions among satellites. In DTN networking environments, it is very important to secure a scheme that has relatively low routing overhead and high reliability, so that it can enhance the overall routing speed and performance. In order for achieving efficient data transmissions among the nodes that have comparatively periodic moving patterns, this paper proposes a time information based DTN routing scheme which is able to predict routing paths. From the simulation results using Omnet++ simulation tools, it has been verified that the proposed time information based DTN routing algorithm shows satisfied levels of routing speed and routing reliability even with lower routing overheads.

• The KIPS Transactions:PartC
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• v.16C no.4
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• pp.521-526
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• 2009

Disruption/Delay Tolerant Network(DTN) is a technology for interconnecting partitioned networks. These days, DTN, especially routing in DTN, draws significant attention from the networking community. In this paper, we investigate DTN routing strategies for highly partitioned ad hoc networks where Unmanned Aerial Vehicles (UAVs) perform store-carry-forward functionality for improved network connectivity. Also we investigate UAV trajectory control mechanisms via simulation studies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.2
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• pp.189-197
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• 2016

Mobile ad-hoc networks (MANETs) experience frequent link disconnections due to non-uniform node distribution and mobility. Thus, end-to-end path establishment-based routing protocols cause frequent transmission failures in MANETs, resulting in heavy control messages for path reestablishment. While location-based MANET routing protocols, such as Greedy Perimeter Stateless Routing (GPSR), use location information to forward messages in a hop-by-hop routing fashion without an end-to-end path establishment procedure, such protocols encounter communication void problems when message forwarding to the next hop fails due to the absence of a relay node. Therefore, to solve this problem, this paper proposes a Delay Tolerant-GPSR (DT-GPSR) protocol, which combines Delay Tolerant Networking (DTN) technology with the GPSR protocol. The performance of DT-GPSR is compared with the performances of the original GPSR and PRoPHET routing protocols through simulation using NS-2. The simulation results confirm that DT-GPSR outperforms GPSR and PRoPHET in terms of the message delivery ratio and message delivery delay.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.1
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• pp.47-53
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• 2012

Sensor networks and car networks that have different structure from that of conventional TCP/IP network require extreme network environment due to frequent change of connectivity. Because such extreme network environment has characteristics like unreliable link connectivity, long delay time, asymmetrical data transfer rate, and high error rate, etc., it is difficult to perform normally with the conventional TCP/P-based routing. DTNs (delay and disruption tolerant network) was designed to support data transfer in extreme network environment with long delay time and no guarantee for continuous connectivity between terminals. This study suggests an algorithm that limits the maximum number of copying transferred message to L by improving the spray and wait routing protocol, which is one of the conventional DTNs routing protocols, and using the azimuth and density data of the mobile nods. The suggested algorithm was examined by using ONE, a DTNs simulator. As a result, it could reduce the delay time and overhead of unnecessary packets compared to the conventional spray and wait routing protocol.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.1
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• pp.83-90
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• 2010

DTNs (Delay Tolerant Networks) refer to the networks that can support data transmission in the extreme networking situations such as continuous delay and no connectivity between ends. DTMNs (Delay Tolerant Networks) are a specific range of DTNs, and its chief considerations in the process of message delivery in the routing protocol are the transmission delay, improvement of reliability, and reduction of network loading. This article proposes a new LCN (Largest Common Neighbor) routing algorism to improve Spray and Wait routing protocol that prevents the generation of unnecessary packets in a network by letting mobile nodes limit the number of copies of their messages to all nodes to L. Since higher L is distributed to nodes with directivity to the destination node and the maximum number of common neighbor nodes among the mobile nodes based on the directivity information of each node and the maximum number of common neighbor nodes, more efficient node transmission can be realized. In order to verify this proposed algorism, DTN simulator was designed by using ONE simulator. According to the result of this simulation, the suggested algorism can reduce average delay and unnecessary message generation.

• Electronics and Telecommunications Trends
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• v.32 no.4
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• pp.67-77
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• 2017

최근 이슈가 되고 있는 자율주행차(Autonomous vehicle 또는 Self-driving car)를 실현하기 위해서는, 다양한 환경에서도 차량에 대한 끊김 없는 연결을 제공하는 커넥티드카(Connected car) 기술이 필수적이다. 현재 커넥티드카를 구현하기 위한 차량 네트워크(Vehicular network) 기술은 교통시스템 인프라 기반의 단일홉(Single-hop) 무선통신 기술이 주를 이루고 있다. 이러한 단일홉 통신은 커버리지가 교통시스템 인프라가 구축된 지역으로 제한된다. 따라서 차량 네트워크가 현재보다 더욱 넓은 지역을 커버하기 위해서는 차량 자체가 이동형 라우터 역할을 수행하여 차량 간의 전달을 통해 정보를 원거리로 전달할 수 있는 다중홉(Multi-hop) 통신 도입이 필요하다. 다중홉 차량 네트워크는 차량의 높은 동적 특성으로 인해 다수의 도전적인 기술적 이슈들을 가진다. 본고에서는 이러한 기술 이슈 중 차량 네트워크의 높은 이동성으로 발생할 수 있는 종단 노드 간 비연결성을 해결할 수 있는 기술인 지연감내형 차량 네트워킹(Delay-tolerant vehicular networking) 기술에 대한 주요 연구 동향을 살펴보고자 한다. 이를 위해 먼저 지연감내형 차량 네트워킹의 기술적 배경 및 주요 관련 기술들을 분석하고 이를 기반으로 향후 연구개발이 필요한 기술 이슈들을 정리한다.

• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.130-136
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• 2009

Delay and Disruption Tolerant Network (DTN) employs message delivery based on a store-and-forward method to conquer no guarantee of continuous end-to-end connectivity. Different from general networks, it is hard for the existing TCP/IP-based routing protocols to correctly work, due to the characteristics such as large latency and unstable link connectivity. Thus, many recent studies focus on routing protocols for DTN. In this paper, we propose a novel routing protocol for DTN with efficient message delivery utilizing mobility information such as direction or destination of mobile nodes. And this protocol is enhanced in terms of delivery ratio, decreases latency and overhead compared to the previously proposed solutions. Simulation results prove its superiority.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.404-407
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• 2014

Delay Tolerant Network (DTN) is a networking architecture that is designed to solve network problem in unstable and stressed environments using the Store-Carry-Forward method. Different form general networks, DTN does not guarantee the end-to-end connectivity, it is hard for the exiting TCP/IP based protocols to normally work due to the characteristic such as large latency and unstable link connectivity. And the condition that send massage without the information of the destination occurs frequently. Thus, suitable routing protocols for DTN are required and being researched. In this paper, we propose a novel routing protocol for DTN utilizing epidemic and prediction based algorithm to prevent the defect of previously DTN routing protocols such as the absence of the holistic view of the network. Proposed algorithm predicted destination using the mobility information recorded in neighbor node's history and utilize epidemic based algorithm when occurred condition without destination's information. This algorithm is enhanced in terms of delivery ratio, decreases latency and overhead in sparse network such as DTN.

• Journal of KIISE:Information Networking
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• v.36 no.2
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• pp.137-142
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• 2009

In traditional message ferrying schemes, only ferries carry messages between partitioned networks. In this paper, we propose a new approach to make both ferries and mobile nodes carry messages so that we reduce message delivery delay in disruption tolerant networks. We evaluate our scheme against conventional message ferrying in terms of message delivery delay, throughput, ferry buffer usage and mobile nodes buffer usage.