• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.1
• /
• pp.87-96
• /
• 2013

Influence propagation is an important research issue in social networks. Influence propagation means that the status or the disposition of nodes get changed by new idea, information and gossip propagated by other nodes. Influenced nodes also make other nodes influenced across the network. The influence propagation problem based on 'word of mouth' referral is to find most influential nodes set in networks to maximize influence. In this paper, we study the influence measuring and finding most influential nodes set in Delay-Tolerant Networks. It is difficult to measure exact influential power in Delay-Tolerant networks where network topology is not stable due to the nodal mobility. In this paper, we propose a distributed scheme that each node constructs $k$-clique community structure and estimates local influential power in Delay-Tolerant Networks. Simulation results show that the influential nodes information estimated by proposed scheme is in agreement with a global view of influential nodes information.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.765-768
• /
• 2012

사회관계망에서 영향력 전파 문제는 네트워크에 가장 영향력을 끼칠 수 있는 노드들을 찾아 전체 네트워크에 영향력을 최대화 하는 것을 목적으로 한다. 본 논문에서는 Delay-Tolerant Networks에서 각 노드의 영향력을 측정하여 가장 영향력 있는 노드 집합을 선택하는 문제를 다룬다. 노드 간 연결성이 항시 보장되지 않는 Delay-Tolerant Networks 환경에서는 전체 네트워크 정보를 정확히 알 수 없기 때문에 노드의 영향력을 정확히 측정하는 것은 매우 어렵다. 본 논문에서는 Delay-Tolerant Networks 환경에서 분산 방식으로 각자 노드가 k-Clique 구조로 커뮤니티를 구성하여 국지적 정보 (Local Information)만을 활용하여 자신의 영향력을 추정하는 방법을 제시하고 실험을 통해 제안 기법으로 산출한 노드들의 영향력이 전체 네트워크 관점에서 산출한 노드들의 영향력에 근접함을 실험을 통해 증명한다.

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

• International Journal of Computer Science & Network Security
• /
• v.22 no.2
• /
• pp.167-174
• /
• 2022

Vehicular Ad hoc Networks are considered as special kind of Mobile Ad Hoc Networks. VANETs are a new emerging recently developed, advanced technology that allows a wide set of applications related to providing more safety on roads, more convenience for passengers, self-driven vehicles, and intelligent transportation systems (ITS). Delay Tolerant Networks (DTN) are networks that allow communication in the event of connection problems, such as delays, intermittent connections, high error rates, and so on. Moreover, these are used in areas that may not have end-to-end connectivity. The expansion from DTN to VANET resulted in Vehicle Delay Tolerant Networks (VDTN). In this approach, a vehicle stores and carries a message in its buffer, and when the opportunity arises, it forwards the message to another node. Carry-store-forward mechanisms, packets in VDTNs can be delivered to the destination without clear connection between the transmitter and the receiver. The primary goals of routing protocols in VDTNs is to maximize the probability of delivery ratio to the destination node, while minimizing the total end-to-end delay. DTNs are used in a variety of operating environments, including those that are subject to failures and interruptions, and those with high delay, such as vehicle ad hoc networks (VANETs). This paper discusses DTN routing protocols belonging to unicast delay tolerant position based. The comparison was implemented using the NS2 simulator. Simulation of the three DTN routing protocols GeOpps, GeoSpray, and MaxProp is recorded, and the results are presented.

• Journal of Applied Reliability
• /
• v.12 no.3
• /
• pp.215-224
• /
• 2012

This paper deals with a design of fault tolerant state feedback controllers for continuous time nonlinear time delay systems with actuator failures. The goal is to find an asymptotically stabilizing controller such that the closed loop system achieves the prescribed $H_{\infty}$ performance objective in the actuator fault cases. Based on a sum of squares (SOS) approach, a design method for $H_{\infty}$ fault tolerant controller is presented. In order to demonstrate our design method, a numerical example is provided.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.2
• /
• pp.149-159
• /
• 2008

This paper considers the problem of adaptive fault-tolerant guaranteed cost controller design via dynamic output feedback for a class of linear time-delay systems against actuator faults. A new variable gain controller is established, whose gains are tuned by the designed adaptive laws. More relaxed sufficient conditions are derived in terms of linear matrix inequalities (LMIs), compared with the corresponding fault-tolerant controller with fixed gains. A real application example about river pollution process is presented to show the effectiveness of the proposed method.

• International Journal of Computer Science & Network Security
• /
• v.23 no.1
• /
• pp.153-163
• /
• 2023

This study is situated in the context of intelligent transport systems, where in-vehicle devices assist drivers to avoid accidents and therefore improve road safety. The vehicles present in a given area form an ad' hoc network of vehicles called vehicular ad' hoc network. In this type of network, the nodes are mobile vehicles and the messages exchanged are messages to warn about obstacles that may hinder the correct driving. Node mobilities make it impossible for inter-node communication to be end-to-end. Recognizing this characteristic has led to delay-tolerant vehicular networks. Embedded devices have small buffers (memory) to hold messages that a node needs to transmit when no other node is within its visibility range for transmission. The performance of a vehicular delay-tolerant network is closely tied to the successful management of the nodes' transit buffer. In this paper, we propose a message transit buffer management model for nodes in vehicular delay tolerant networks. This model consists in setting up, on the one hand, a policy of dropping messages from the buffer when the buffer is full and must receive a new message. This drop policy is based on the concept of intermediate node to destination, queues and priority class of service. It is also based on the properties of the message (size, weight, number of hops, number of replications, remaining time-to-live, etc.). On the other hand, the model defines the policy for selecting the message to be transmitted. The proposed model was evaluated with the ONE opportunistic network simulator based on a 4000m x 4000m area of downtown Bouaké in Côte d'Ivoire. The map data were imported using the Open Street Map tool. The results obtained show that our model improves the delivery ratio of security alert messages, reduces their delivery delay and network overload compared to the existing model. This improvement in communication within a network of vehicles can contribute to the improvement of road safety.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.6
• /
• pp.2180-2200
• /
• 2015

This paper considers mobility control to improve packet delivery in delay-tolerant networks (DTNs) under group mobility. Based on the group structure in group mobility, we propose two mobility control techniques; group formation enforcement and group purposeful movement. Both techniques can be used to increase the contact opportunities between groups by extending the group's reachability. In addition, they can be easily integrated into some existing DTN routing schemes under group mobility to effectively expedite the packet delivery. This paper is divided into 2 parts. First, we study how our proposed mobility control schemes reduce the packet delivery delay in DTNs by integrating them into one simple routing scheme called group-epidemic routing (G-ER). For each scheme, we analytically derive the cumulative density function of the packet delivery delay to show how it can effectively reduce the packet delivery delay. Then, based on our second proposed technique, the group purposeful movement, we design a new DTN routing scheme, called purposeful movement assisted routing (PMAR), to further reduce the packet delay. Extensive simulations in NS2 have been conducted to show the significant improvement of PMAR over G-ER under different practical network conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.12
• /
• pp.54-60
• /
• 2005

In this paper, fault tolerant control for aircraft is being discussed. The authors propose a fault tolerant control algorithm based on time delay control. Time delay control is an effective method to deal with unknown dynamics. The proposed algorithm has no parameter to be updated and needs no prior information of faults. These are the primary advantages of the proposed method. The algorithm uses output feedback. The design and the stability condition are presented by following the existing proof. The proposed algorithms are verified by simulation examples.

• KIPS Transactions on Computer and Communication Systems
• /
• v.3 no.1
• /
• pp.15-22
• /
• 2014

Delay-Tolerant Network employs message forwarding based on a Store, Carry and Forward method to conquer no guarantee of continue connectivity. For this reason, a lot of DTN routing scheme have been proposed recently. message forwarding is an important research issue in delay-tolerant network and In this paper, we propose a efficiency DTN routing scheme using node's social relation and expanded Ego-network betweenness centrality. Our simulation results show that it is more efficient to message delivery cost than Epidemic routing, Friendship routing while it has a little performance degradation of message delivery ratio.