• International Journal of Fuzzy Logic and Intelligent Systems
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• v.14 no.4
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• pp.295-304
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• 2014

Communication infrastructure supports wide variety of mobile services such as photo and file sharing, location tracking, social network services and instant messaging. However, instances like power-loss and natural disasters disrupt these communication infrastructures unable to render support to these mobile services. Delay-tolerant networks (DTNs) offer a solution to these problems at hand. By utilizing mobility and opportunistic contacts among mobile devices, a plausible communication network can be establish and enable support to mobile applications. This paper presents an energy-efficient, reliable message delivery routing scheme with message prioritization rules for DTN. It uses the context information of nodes (mobile devices) such as the contact history (location and time of contact), speed/velocity, moving direction to determine the best forwarders among nodes in the network. The remaining energy of the nodes is also used to determine the message types a node can deliver successfully. The simulation results show that proposed approach outperforms Epidemic and Prophet routing schemes in terms of delivery ratio, overhead ratio, delivered messages per types and remaining energy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.105-106
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• 2015

본 논문에서는 DTN(Delay Tolerant Network) 환경에서 효율적인 메시지 전달을 위해 확률적으로 중계 노드를 선택하는 기법을 제안한다. DTN은 종단 간 연결이 불확실한 네트워크에서의 통신을 Store-Carry-Forward 방식을 사용하여 메시지를 목적 노드에 전달한다. 또한 종단 간 연결이 불확실한 상황에서도 중계 노드를 통해 메시지를 목적 노드에 전달하여 높은 전송률을 보장한다. 하지만 에피데믹(Epidemic) 라우팅이나 Spray and Wait 라우팅과 같은 기존 다중 복사 라우팅 알고리즘은 접촉한 모든 노드에게 메시지를 복사하여 메시지 복사로 인한 오버헤드가 높아진다. 반면에 PROPHET 라우팅과 같은 단일 복사 알고리즘은 적은 오버헤드를 발생시키지만 중계 노드 수 감소로 인한 메시지 전송률 감소 현상이 나타난다. 본 논문에서 제안하는 알고리즘은 기존 DTN 라우팅의 문제점을 보완하기 위해 확률적으로 노드 분포를 분석하여 현재 네트워크에 효율적인 메시지 복사 방식을 선택하여 작동한다. 본 논문에서는 제안하는 알고리즘이 기존 DTN 라우팅 알고리즘과 오버헤드와 전송률을 비교하여 더 효율적임을 증명한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.173-175
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• 2022

서로 다른 수중 통신 매체 사이의 각기 다른 장단점을 해결하기 위해 여러 종류의 수중 통신 모듈을 함께 운용하는 통신 기술인 다중매체 통신 기술이 등장하였다. 다중매체 통신은 한 네트워크에서 서로 다른 통신 매체들을 함께 운용하기 때문에 이들의 전송 속도 차이로 인한 흐름 제어 문제가 발생한다. 이에 본 논문에서는 통신 속도 차이로 인한 전송데이터 손실을 미연에 방지하는 수중 다중매체 통신에서 전송데이터 흐름을 제어하는 일종의 DTN (Delay/ Disruption Tolerant Network) 프로토콜을 제안한다. 이 전송 속도 제어 프로토콜을 이용하여 수중 다중매체 통신 네트워크에서 전송 속도 차이로 인해 한 노드에 메시지가 쌓여 전송 큐의 전송데이터 손실이 예측되는 경우 보조 저장장치를 이용하여 큐의 길이를 늘이고, 보조 저장장치 또한 전송데이터 손실이 예측되는 경우 전송 중인 노드에 전송 일시중지를 요청하며 지연상태가 해결된 후 다시 전송을 요청할 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1046-1049
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• 2010

Custody transfer method is often managed by the general architecture of Delay Tolerant Network (DTN) to provide reliability in the communications through storage and forward paradigm, but can be inefficient when the acknowledgment messages are lost, or the network becomes congested. In this paper we describe a new architecture that is particularly efficient for the custody transfer method. Because, it provides an additional control of acknowledgment messages, consolidate knowledge and services, using the advantage of the cross-over architectures and distribution control through local and global services.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.1009-1016
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• 2015

In this paper, we propose EPCM(Efficient Prediction-based Context-awareness Matrix) algorithm analyzing connectivity by predicting cluster's context data such as velocity and direction. In the existing DTN, unrestricted relay node selection causes an increase of delay and packet loss. The overhead is occurred by limited storage and capability. Therefore, we propose the EPCM algorithm analyzing predicted context data using context matrix and adaptive revision weight, and selecting relay node by considering connectivity between cluster and base station. The proposed algorithm saves context data to the context matrix and analyzes context according to variation and predicts context data after revision from adaptive revision weight. From the simulation results, the EPCM algorithm provides the high packet delivery ratio by selecting relay node according to predicted context data matrix.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.3
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• pp.37-41
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• 2020

In this paper, we propose a routing method to improve the message transmission efficiency between DTN nodes in an environment where communication infrastructure in the city is destroyed. In the situation where a certain size of communication infrastructure can not function, the message transmission process between the nodes is explained. An effective routing method for improving reliability between nodes was proposed and evaluated using DTN simulator. The routing algorithm with improved reliability in urban areas was confirmed by simulation considering the message transmission relationship between nodes on uncertain path due to the destruction of communication infrastructure. We used a routing algorithm that includes all the contact information the node has experienced in the past. In the simulation of delivering messages in a situation where the communication infrastructure was destroyed, relatively better results were obtained than the existing routing algorithm.

• Journal of KIISE
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• v.42 no.3
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• pp.408-412
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• 2015

In base station based networks, traffic overload at the base station is inevitable. Peer-to-peer DTN which disperses the traffic overhead to each node can relieve the traffic overload at the base station. To increase the message delivery ratio and reduce the message overhead, we present novel routing using mobility information which can be obtained from each node, unlike the existing flooding based routings. In the proposed routing scheme, the routing decision metric, which is defined based on the node mobility information, is computed by using the expected distance between each node to the destination. The message is copied to other nodes that have lower expected distance to the destination than the value for the node willing to copy the message. We conducted simulations by using both a random mobility model and a real mobility trace to compare the performance of the proposed routing scheme to the existing routing scheme that does not utilize the mobility information. The performance evaluation showed the proposed routing successfully delivers messages with 10% to 30% less copies compared to previously proposed routing schemes.

• Journal of Information Processing Systems
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• v.13 no.3
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• pp.618-629
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• 2017

Mobile nodes can't always connect each other in DTNs (delay tolerant networks). Many DTN routing protocols that favor the "multi-hop forwarding" are proposed to solve these network problems. But they also lead to intolerant delivery cost so that designing a overhead-efficient routing protocol which is able to perform well in delivery ratio with lower delivery cost at the same time is valuable. Therefore, we utilize the small-world property and propose a new delivery metric called multi-probability to design our relay node selection principles that nodes with lower delivery predictability can also be selected to be the relay nodes if one of their history nodes has higher delivery predictability. So, we can find more potential relay nodes to reduce the forwarding overhead of successfully delivered messages through our proposed algorithm called HESnW. We also apply our new messages copies allocation scheme to optimize the routing performance. Comparing to existing routing algorithms, simulation results show that HESnW can reduce the delivery cost while it can also obtain a rather high delivery ratio.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.211-212
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• 2008

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.120-128
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• 2014

Adventure of human race for space exploration is toward outer region of solar system. Recently the main targets of space explorations are becoming mainly the Mars, Venus and asteroids instead of the Moon which was the popular place human wants to explore. There are several technical challenges as spacecraft goes far and far away from the Earth, and among them communication protocol is one of the most challenging problems. In this paper, several international technical trends regarding deep space communication protocol technologies in an aspect of software implementation is presented. It is expected that these references are helpful for the development of the lunar orbiter pathfinder which is planned to be launched in 2017.