• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.750-752
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• 2010

MANET has some interest as a wireless mobile network supporting node mobility and having no additional infrastructure. Speed of mobile node on MANET is various from just slow speed of human's walk to vehicle's moving speed. In this study, VoIP performance of MANET is evaluated in the view of speed of mobile node. VoIP performance is studied on walking speed, vehicle speed and higher speed on MANET. PDR(Packet Delivery Ratio), MOS(Mean Opinion Score) are used as performance parameters.

• Journal of Internet Computing and Services
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• v.5 no.3
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• pp.25-33
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• 2004

Mobile IP Low Latency Handoffs(l) allow greater support for real-time services on a Mobile IP network by minimizing the period of time when a mobile node is unable to send or receive IP packets due to the delay in the Mobile IP Registration process. However, on Mobile IP network with AAA servers that are capable of performing Authentication, Authorization, and Accounting(AAA) services, every Registration has to be traversed to the home network to achieve new session keys, that are distributed by home AAA server, for a new Mobile IP session. This communication delay is the time taken to re-authentication the mobile node and to traverse between foreign and home network even if the mobile node has been previously authorized to old foreign agent. In order to reduce these extra time overheads, we present a method that performs Low Latency Handoffs without requiring further involvement by home AAA server. The method re-uses the previously assigned session keys. To provide confidentiality and integrity of session keys in the phase of key exchange between agents, it uses a key sharing method by gateway foreign agent that performs a trusted thirty party. The proposed method allows the mobile node to perform Low Latency Handoffs with fast as well as secure operation.

• Journal of the Korea Society of Computer and Information
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• v.22 no.10
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• pp.55-62
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• 2017

In this paper, we proposes a multi-ring based mobile sink location scheme for solar-powered wireless sensor network (WSN). The proposed scheme maintains the multi-rings in which nodes keep the current location of sink node. With the help of nodes in multi-rings, each node can locate the sink node efficiently with low-overhead. Moreover, because our scheme utilizes only surplus energy of a node, it can maintain multiple rings without degrading any performance of each node. Experimental results show that the proposed scheme shows much better latency and scalability with lower energy-consumption than the existing single-ring based scheme.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.238-245
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• 2016

A sequence number checking technique is proposed to improve the performance of TCP connections in mobile ad hoc networks. While a TCP connection is initialized, a routing protocol takes the responsibility for checking the hop count between a source and destination pair. If the hop count is greater than a predefined value, the routing protocol decides to use a proxy node. The responsibility of a proxy node is to check the correctness of data packets and inform the missing packets by sending an acknowledgement from a proxy node to the source node. By doing so, the source node is able to retransmit any missing packet in advance without waiting until an end-to-end acknowledgement is received from the destination. Simulation results show that the proposed mechanism is able to increase throughput up to 55% in static network and decrease routing overhead up to 95%in mobile network.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.1
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• pp.11-14
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• 2015

WSN (Wireless Sensor Network) based on low-power is one of the core technologies in the ubiquitous society. In this paper, we present a border surveillance and control system in WSN environment. The system consists of static sensor node, mobile sensor node, static gateway, mobile gateway, server and mobile application. Mobile applications are divided into user mode and manager mode. So users monitor border surveillance through mobile phone and get information of border network environment without time and space constraints. In manager mode, for the flexible operation of nodes, manager can update to the software remotely and adjust the position of the mobile node. And also we implement a suitable multi-hop routing protocol for scalable low-power sensor nodes and confirm that the system operates well in WSN environment.

• Journal of Korea Multimedia Society
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• v.11 no.4
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• pp.544-553
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• 2008

The general sensor network uses bundle method to collect fixed information from sensor node. However, this method is difficult to actively cope with major sensing objects in healthcare environment including status and position change of person and change of surrounding environment. In order to support the healthcare environment, certain information should be provided in accordance with the change of status of person and surrounding circumstance and also must cope with the change of network type by movement of person. This paper analyzes LEACH protocol which guarantees effectiveness of network as it constitutes clusters between Agilla model that is a representative multi agent middle ware and surrounding nodes. Based on the result of this analysis, it suggests LEACH_Mobile protocol which guarantees node mobility that is the weakest point of LEACH protocol. Moreover, it designs mobility agent middleware which supports dynamic function change of node and mobility agent module which supports dynamic function change of mobile node as components of LEACH_Mobile routing module. In addition, it is definitely increase performance which in mobile node of transfer data rate through LEACH_Mobile protocol of simulation result.

• Journal of Korea Society of Digital Industry and Information Management
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• v.12 no.3
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• pp.75-85
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• 2016

MANET is a network composed only mobile network having limited resources and has dynamic topology characteristics. Therefore, every mobile node acts as a route and delivers data by using multi-hop method. In particular, group communication such as multicast is desperately needed because of characteristics such as battery life of limited wireless bandwidth and mobile nodes. However, the multicast technique can have different efficient of data transmission according to configuring method of a virtual topology by the movement of the nodes and the performance of a multicast can be significantly degraded. In this paper, the region based security multicast technique is proposed in order to increase the efficiency of data transmission by maintaining an optimal path and enhance the security features in data transmission. The group management node that manages the state information of the member nodes after the whole network is separated to area for efficient management of multicast member nodes is used. Member node encrypts using member key for secure data transmission and the security features are strengthened by sending the data after encrypted using group key in group management node. The superiority of the proposed technique in this paper was confirmed through experiments.

• Journal of the Korea Society of Computer and Information
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• v.9 no.3
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• pp.171-175
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• 2004

This paper proposes a seamless handoff scheme that enables a mobile node to continue a session when moving to an overlapping area. During handoff due to the weakness of signaling, mobile node makes new Care-of Addresses using signals received from access router when MN reaches the edge of its area in addition to its current CoA, and it sends temporary binding update messages to Mobility Anchor Point which manage the area covering MN. MAP receives that binding update messages from MN, and temporarily stores new binding informations from them to its binding cache besides existing binding information for MN. This scheme ensures a seamlessly handoff using multicasting until MN enter a new access router area and sends a confirmed binding update message to MAP.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.58-60
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• 2003

Mobile IP는 현재의 인터넷에서 노드가 링크를 변화시킬 때 통신이 지속 될 수 있도록 이동성(Mobility)을 제공하기 위한 방안이다. Mobile IP는 MN(Mobile Node)이 HA(Home Agent) 와 FA(Foreign Agent)사이에서 링크를 변화시킬 때 CN(Correspondent Node)과 지속적인 통신을 할 수 있도록 한다. 그러나 FA에서 FA로 MN이 노드의 위치를 바꿀 때에는 핸드오프(Handoff)가 발생하여 패킷이 손실 될 수도 있다. 본 논문은 MN이 FA에서 다른 FA로 이동할 때 발생하는 패킷 손실과 순서변경에 대한 경우를 살펴 이를 해결하기 위한 Seamless 핸드오프 프로토콜을 기술하고 이를 검증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4738-4753
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• 2018

Efficient rendezvous node selection and routing algorithm (RNSRA) for wireless sensor networks with mobile sink that visits rendezvous node to gather data from sensor nodes is proposed. In order to plan an optimal moving tour for mobile sink and avoid energy hole problem, we develop the RNSRA to find optimal rendezvous nodes (RN) for the mobile sink to visit. The RNSRA can select the set of RNs to act as store points for the mobile sink, and search for the optimal multi-hop path between source nodes and rendezvous node, so that the rendezvous node could gather information from sensor nodes periodically. Fitness function with several factors is calculated to find suitable RNs from sensor nodes, and the artificial bee colony optimization algorithm (ABC) is used to optimize the selection of optimal multi-hop path, in order to forward data to the nearest RN. Therefore the energy consumption of sensor nodes is minimized and balanced. Our method is validated by extensive simulations and illustrates the novel capability for maintaining the network robustness against sink moving problem, the results show that the RNSRA could reduce energy consumption by 6% and increase network lifetime by 5% as comparing with several existing algorithms.