• 한국멀티미디어학회논문지
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• 제24권1호
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• pp.51-57
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• 2021

In this paper, we propose a task distribution scheme in fog computing environment considering opportunistic fog computing nodes. As latency is one of the important performance metric for IoT(Internet of Things) applications, there have been lots of researches on the fog computing system. However, since the load can be concentrated to the specific fog computing nodes due to the spatial and temporal IoT characteristics, the load distribution should be considered to prevent the performance degradation. Therefore, this paper proposes a task distribution scheme which considers the static as well as opportunistic fog computing nodes according to their mobility feature. Especially, based on the task requirements, the proposed scheme supports the delay sensitive task processing at the static fog node and delay in-sensitive tasks by means of the opportunistic fog nodes for the task distribution. Based on the performance evaluation, the proposed scheme shows low service response time compared to the conventional schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권7호
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• pp.3018-3040
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• 2018

The mobility model is one of the most important factors that impacts the evaluation of any transportation vehicular networking protocols via simulations. However, to obtain a realistic mobility model in the dynamic urban environment is a very challenging task. Several studies extract mobility models from large-scale real data sets (mostly taxi GPS data) in recent years, but they do not consider the statuses of taxi, which is an important factor affected taxi's mobility. In this paper, we discover three simple observations related to the taxi statuses via mining of real taxi trajectories: (1) the behavior of taxi will be influenced by the statuses, (2) the macroscopic movement is related with different geographic features in corresponding status, and (3) the taxi load/drop events are varied with time period. Based on these three observations, a novel taxi mobility model (T-START) is proposed with respect to taxi statuses, geographic region and time period. The simulation results illustrate that proposed mobility model has a good approximation with reality in trajectory samples and distribution of nodes in four typical time periods.

• Journal of Information Processing Systems
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• 제12권2호
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• pp.275-294
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• 2016

A primary task in wireless sensor networks (WSNs) is data collection. The main objective of this task is to collect sensor readings from sensor fields at predetermined sinks using routing protocols without conducting network processing at intermediate nodes, which have been proved as being inefficient in many research studies using a static sink. The major drawback is that sensor nodes near a data sink are prone to dissipate more energy power than those far away due to their role as relay nodes. Recently, novel WSN architectures based on mobile sinks and mobile relay nodes, which are able to move inside the region of a deployed WSN, which has been developed in most research works related to mobile WSN mainly exploit mobility to reduce and balance energy consumption to enhance communication reliability among sensor nodes. Our main purpose in this paper is to propose a solution to the problem of deploying mobile data collectors for alleviating the high traffic load and resulting bottleneck in a sink's vicinity, which are caused by static approaches. For this reason, several WSNs based on mobile elements have been proposed. We studied two key issues in WSN mobility: the impact of the mobile element (sink or relay nodes) and the impact of the mobility model on WSN based on its performance expressed in terms of energy efficiency and reliability. We conducted an extensive set of simulation experiments. The results obtained reveal that the collection approach based on relay nodes and the mobility model based on stochastic perform better.

• 인터넷정보학회논문지
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• 제13권3호
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• pp.31-47
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• 2012

IETF(Internet Engineering Task Force)의 MVPN(Mobile Virtual Private Network) 은 NEMO(NEtwork MObility)를 지원하도록 설계되어 있지 않기 때문에 실시간 응용에 적합하지 않다. 따라서 안전한 NEMO에서 VPN을 지원하는 아키텍처와 프로토콜이 필요하다. 본 논문에서는 VPN 환경에서 실시간 응용을 위해 설계된, SIP(Session Initiation Protocol)에 기반한 CR-SeMMS(Cost-Reduced Secure Mobility Management Scheme) 시스템을 제안한다. 제안하는 기법은 NEMO에서의 MVPN을 지원하는 방법을 제안하여 전체 네트워크가 이동하는 경우, 지속적으로 세션을 유지하도록 한다. 또한, 핸드오프의 경우 지연 시간 요소로 고려되는 인증 시간을 단축하기 위하여 HOTP(HMAC based One Time Password) 기반의 인증방식을 이용한 핸드오프 방식을 제안하여 세션을 유지하기 위해 지속적으로 발생하는 시그널링 처리시간을 개선하였다. 마지막으로, 제안한 방식과 기존 방식을 시뮬레이션하여 핸드오프 수행의 평균 시간이 개선되는 것을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권4호
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• pp.1661-1678
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• 2016

Clustering is one of the key technologies in vehicular networks. Constructing and maintaining stable clusters is a challenging task in high mobility environments. DWCM (Distributed and Weighted Clustering based on Mobility Metrics) is proposed in this paper based on the d-hop dominating set of the network. Each vehicle is assigned a priority that describes the cluster relationship. The cluster structure is determined according to the d-hop dominating set, where the vehicles in the d-hop dominating set act as the cluster head nodes. In addition, cluster maintenance handles the cluster structure changes caused by node mobility. The rationality of the proposed algorithm is proven. Simulation results in the NS-2 and VanetMobiSim integrated environment demonstrate the performance advantages.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2002년도 봄 학술발표논문집 Vol.29 No.1 (A)
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• pp.580-582
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• 2002

차세대 인터넷의 기반이 되고 있는 IPv6(Internet Protocol version 6, RFC2460)상에서 이동성(Mobility)을 지원하기 위하여 IETF(Internet Engineering Task Force)에서는 Mobile IPv6에 대한 표준화 작업을 진행 중에 있다. 본 논문에서는 라우터, 홈에이전트와 외부네트워크라우터 등의 접근노드, 대응노드, 이동단말 등의 구성요소를 활용하여 IPv6 상에서 이동성지원시스템을 구축하였으며 구축된 시스템에서 Mobile IPv6 기능 및 성능 평가를 수행하였다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2003년도 봄 학술발표논문집 Vol.30 No.1 (C)
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• pp.509-511
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• 2003

최근 이동 통신 환경에서의 인터넷 서비스의 요구가 늘어남에 따라 IP의 이동성 지원에 대한 연구가 활발히 진행되어 왔다. 본 논문은 IP 이동성 지원을 위한 프로토콜 중 IETF(Internet Engineering Task Forces)에서 현재 표준화가 진행중인 HMIPv6(Hierarchical Mobile IPv6 Mobility Management)[4]가 가지는 부하 분산 문제를 수평적인 MAP(Mobility Anchor Point) 구조를 통해 해결하고, 이 구조에서의 페이징 지원 방안을 제안하였다.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.987-992
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• 2016

This study introduces an example environment where wireless devices are mobile, devices use dynamic voltage scaling, devices and tasks are heterogeneous, tasks have deadline, and the computation and communication power is dynamically changed for energy saving. For this type of environment, the efficient system-level energy management and resource management for task completion can be an essential part of the operation and design of such systems. Therefore, the resources are assigned to tasks and the tasks may be scheduled to maximize a goal which is to minimize energy usage while trying to complete as many tasks as possible by their deadlines. This paper also introduces mobility of nodes and variable transmission power for communication which complicates the resource management/task scheduling problem further.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1344-1367
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• 2014

Mobile traffic is increasing a masse because of the propagation of the Internet and the development of wireless mobile technology. Accordingly, the Network Local Mobility Management (NETLMM) working group [1] of the Internet Engineering Task Force (IETF) has standardized Proxy Mobile IPv6 (PMIPv6) [2] as a protocol for accomplishing the transmissibility of mobile terminals. PMIPv6 is a network-led IP-based mobility management protocol, which can control terminal mobility without depending on the type of access system or the capability of the terminal. By combining PMIPv6 and the mobility of Session Initiation Protocol (SIP), we can establish terminal mobility and session mobility through a more effective route. The mobility function can be improved and the overlap of function reduced as compared to that in the case of independent operation. PMIPv6 is appropriate for a non-real-time service using TCP, and SIP is appropriate for a real-time service using RTP/UDP. Thus, in the case of a terminal using both services, an effective mobility management is possible only by using PMIPv6 together with SIP. In order to manage mobility in this manner, researches on PMIPv6-SIP are in progress. In line with this trend, this paper suggests a new PMIPv6-SIP architecture where when a mobile terminal conducts a handover, a network-led handover while maintaining the session without the addition of a special function or middleware is possible along with effective performance evaluation through mathematical modeling by comparing the delay and the packet loss that occur during the handover to the Pure-SIP.

• 한국정보과학회논문지:정보통신
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• 제27권2호
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• pp.219-225
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• 2000

적절한 이동 인터넷 서비스를 제공하기 위해서는 IP의 이동성을 제공하는 Mobile IP의 지원이 필요하며 이를 위한 서비스 네트웍의 구축을 위해서는 속도, 확장성 그리고 서비스 제공능력이 뛰어난 IETF(Internet Engineering Task Force)의 MPLS(Multi-protocol Label Switching)로 구성이 바람직하다. 본 논문은 현재 MPLS표준화에서 이동성을 지원하는 노력을 하고있지 않은 상태에서 Mobile IP를 효율적으로 수용하는 MPLS 구조를 제시한다. 제시하는 구조는 Mobile IP의 등록 메시지와 MPLS 레이블의 분배를 결합하여 망 내의 터널링 시 3계층의 캡슐화가 아닌 2계층을 터널링을 활용하여 헤더의 남용을 막고 홈 에이전트로 유입되는 패킷들이 이동성 바인딩 리스트를 참조하지 않고 지연 없이 망 내로 터널링 될 수 있는 구조를 보여준다. 제시하는 구조는 특히 무선 망과의 연동과 인터넷과의 연동 기능을 수행하는 IMT-2000망에서 이동 인터넷을 위한 서비스 패킷 망의 기본 구조로 활용될 수 있다.