• Journal of Communications and Networks
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• 제17권2호
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• pp.126-132
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• 2015

In mobile computing research area, it is highly desirable to understand the characteristics of user movement so that the user friendly location aware services could be rendered effectively. Location based social networks (LBSNs) have flourished recently and are of great potential for movement behavior exploration and datadriven application design. While there have been some efforts on user check-in movement behavior in LBSNs, they lack comprehensive analysis of social influence on them. To this end, the social-spatial influence and social-temporal influence are analyzed synthetically in this paper based on the related information exposed in LBSNs. The check-in movement behaviors of users are found to be affected by their social friendships both from spatial and temporal dimensions. Furthermore, a probabilistic model of user mobile behavior is proposed, incorporating the comprehensive social influence model with extent personal preference model. The experimental results validate that our proposed model can improve prediction accuracy compared to the state-of-the-art social historical model considering temporal information (SHM+T), which mainly studies the temporal cyclic patterns and uses them to model user mobility, while being with affordable complexity.

• 한국통신학회논문지
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• 제29권8A호
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• pp.909-917
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• 2004

무선 통신망에서 끊임없는 데이터 전달을 제공하는 것은 실시간 멀티미디어 서비스들에 있어서 매우 주요한 기능들 중의 하나이다 본 논문에서는, IP 이동성 지원을 위한 유망한 방법들인 MIP-RO, SIP, MIP-RO/CIP와 SIP/CIP들에 대한 핸드 오프 지연시간을 분석하고 비교한다. 핸드오프 지연시간 분석은 이들 방법들에 대한 핸드오프 처리를 위하여 교환되는 메시지 플로우를 기반으로 하여 만들었다 실험 결과는 SIP/CIP 방법이 다른 방법들에 비하여 핸드오프 지연시간 측면에서 가장 좋은 성능을 보여준다.

• 한국경영과학회지
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• 제33권3호
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• pp.43-58
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• 2008

In this paper, we have presented a dynamic, predictive location update scheme that takes into account each user's mobility patterns. A user's past movement history is used to create two-dimensional transition probability matrix which makes use of two directional consecutive location areas. A mobile terminal utilizes the transition probability to develop a predictive path which consists of several predictive nodes and then the location update is saved as long as a mobile user follows the predictive path. Using continuous-time Markov chain, cost functions of location update and paging are derived and it is shown that the number of predictive nodes can be determined optimally. To evaluate the proposed scheme, simulations are designed and the numerical analysis is carried out. The numerical analysis features user's mobility patterns and regularity, call arrival rates, and cost ratio of location update to paging. Results show that the proposed scheme gives lower total location management cost, compared to the other location update schemes.

• 한국멀티미디어학회논문지
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• 제17권8호
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• pp.946-952
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• 2014

Mobility prediction is one of hot topics using location history information. It is useful for not only user-level applications such as people finder and recommendation sharing service but also for system-level applications such as hand-off management, resource allocation, and quality of service of wireless services. Most of current prediction techniques often use a set of significant locations without taking into account possible location information changes for prediction. Markov-based, LZ-based and Prediction by Pattern Matching techniques consider interesting locations to enhance the prediction accuracy, but they do not consider interesting location changes. In our paper, we propose an algorithm which integrates the changing or emerging new location information. This approach is based on Active LeZi algorithm, but both of new location and all possible location contexts will be updated in the tree with the fixed depth. Furthermore, the tree will also be updated even when there is no new location detected but the expected route is changed. We find that our algorithm is adaptive to predict next location. We evaluate our proposed system on a part of Dartmouth dataset consisting of 1026 users. An accuracy rate of more than 84% is achieved.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2473-2492
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• 2012

Energy conservation is a vital issue in wireless sensor networks. Recently, employing mobile sinks for data gathering become a pervasive trend to deal with this problem. The sink can follow stochastic or pre-defined paths; however the controlled mobility pattern nowadays is taken more into consideration. In this method, the sink moves across the network autonomously and changes its position based on the energy factors. Although the sink mobility would reduce nodes' energy consumption and enhance the network lifetime, the overhead caused by topological changes could waste unnecessary power through the sensor field. In this paper, we proposed EEDARS, an energy-efficient dual-sink algorithm with role switching mechanism which utilizes both static and mobile sinks. The static sink is engaged to avoid any periodic flooding for sink localization, while the mobile sink adaptively moves towards the event region for data collection. Furthermore, a role switching mechanism is applied to the protocol in order to send the nearest sink to the recent event area, hence shorten the path. This algorithm could be employed in event-driven and multi-hop scenarios. Analytical model and extensive simulation results for EEDARS demonstrate a significant improvement on the network metrics especially the lifetime, the load and the end-to-end delay.

• 한국음향학회지
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• 제31권3호
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• pp.142-150
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• 2012

도파관유한요소법 (waveguide finite element method, WFEM)은 단면의 형상이 길이방향으로 일정한 도파관 구조물의 진동을 해석하기 위한 수치해석 기법이다. 도파관유한요소법은 2차원 단면만을 FE 모델링하여 길이방향 파동 전파를 해석하므로 기존의 유한요소법에 비해 해석 모델의 크기가 작고 연산 시간이 짧다는 장점을 가진다. 본 연구에서는 기존의 도파관유한요소법을 확장하여 내부 및 외부에 유체가 채워진 도파관 구조물에 대한 진동 해석을 수행하였다. 이를 위해 내부 유체와 도파관 구조물은 WFE로, 외부 유체는 파수경계요소 (waveguide boudnary element, WBE)로 모델링하고 이들을 연성시킨 운동방정식을 제시하였다. 이 방법의 적용 예로써 내부에 물이 채워진 몰수된 파이프의 진동 및 방사 음향 파워를 해석하였다. 내부 및 외부 유체의 유/무에 따른 분산 선도와 가진점 모빌리티 (point mobility)를 구하고 유체 연성의 효과를 살펴보았다.

• 유통과학연구
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• 제18권4호
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• pp.5-12
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• 2020

The Purpose: This study aims to identify the characteristics of customer satisfaction of the restaurants delivery applications that is increasing globally, especially in Korea. Due to demographic changes, social trends and the development of food science, customers no longer want to visit restaurants. This represents an important change in the restaurant business, and related research is also very urgent. Research design, data, and methodology: With 296 surveyed questionnaire, the study analyzed to verify the validity and reliability of measured variables in Korea. And structural equation model was used for hypotheses test of the research. Results: The result showed that consumers' usefulness, mobility, and reliability influenced on satisfaction. Specifically, mobility and reliability influencing the satisfaction and loyalty as well. And significant impact of satisfaction and loyalty are also corroborated. However, the path from informative to both satisfaction and loyalty was not statistically significant. This means food application developers should no longer focus on providing too many information, instead, concentrate on improving mobility and trust of mobile applications. Conclusions: This study analyzed the influence of attributes of food delivery applications on satisfaction and loyalty, and suggested crucial strategic implications of delivery marketing companies involved in the implementation of mobile application developers.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1773-1795
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• 2020

Unmanned aerial vehicles (UAVs) network are a very vibrant research area nowadays. They have many military and civil applications. Limited bandwidth, the high mobility and secure communication of micro UAVs represent their three main problems. In this paper, we try to address these problems by means of secure clustering, and a security clustering algorithm based on integrated trust value for UAVs network is proposed. First, an improved the k-means++ algorithm is presented to determine the optimal number of clusters by the network bandwidth parameter, which ensures the optimal use of network bandwidth. Second, we considered variables representing the link expiration time to improve node clustering, and used the integrated trust value to rapidly detect malicious nodes and establish a head list. Node clustering reduce impact of high mobility and head list enhance the security of clustering algorithm. Finally, combined the remaining energy ratio, relative mobility, and the relative degrees of the nodes to select the best cluster head. The results of a simulation showed that the proposed clustering algorithm incurred a smaller computational load and higher network security.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2017년도 춘계학술발표대회
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• pp.113-116
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• 2017

최근 급격히 증가한 모바일 기기와 Over The Top (OTT) 서비스의 활성화로 인하여 CMM 기반의 LTE/EPC 네트워크에 과다한 데이터/제어 트래픽의 수용이 힘들어지는 문제가 중요 이슈로 부각되고 있다. 이를 해결하기 위하여 IETF는 Distributed Mobility Management (DMM) 기반의 이동성 관리 방안을 제안하였다. 하지만 DMM 기술은 중앙의 트래픽 부하 분산에 초점을 두고 있어 단말의 이동과 관련하여 발생하는 과다한 제어 트래픽 수용에 관한 문제를 해결하기에는 부족하다. 따라서 본 논문에서는 이러한 문제를 해결하기 위하여 SDN 기반으로 CMM과 DMM을 함께 이용하는 HMM (Hybrid Mobility Management) LTE/ECP 네트워크 모델을 제시한다. 또한 HMM 기반의 LTE/EPC 네트워크 모델은 CMM 및 DMM 기법의 선택을 위해 단말의 이동성과 PDN 연결의 개수를 고려한 선택방안을 제시하며, 제안하는 HMM 기반의 LTE/EPC 네트워크 구조에서의 데이터 트래픽 부하량과 단말의 이동성과 PDN 연결 개수에 따라 제어 트래픽의 양을 비교하는 그래프를 제시하며 제안하는 네트워크 모델의 타당성을 입증한다.

• 컴퓨터교육학회논문지
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• 제8권6호
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• pp.123-132
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• 2005

이동망의 위치관리에서 위치갱신 비용 최소화를 위한 많은 연구 결과들이 있다. 위치갱신 비용의 최소화를 위해서는 각 사용자들의 이동 패턴을 고려해야만 한다. 본 논문은 과거의 사용자 이동에 대한 이력으로부터 각 사용자에 대한 위치영역 리스트 생성과 이를 위한 3 단계 페이징 방안을 제안한다. 사용자의 이동은 공간적으로 뿐만 아니라 시간적으로도 규칙적인 패턴이 존재한다. 따라서 제안된 위치영역 리스트 생성방안은 이상의 2가지 측면에서 사용자의 방문빈도를 이용하여 규칙성을 발견하고, 이에 대한 위치영역리스트를 생성한다. 제안된 방안의 성능분석 위해서 제안된 방안에 대하여 사용자 이동 패턴을 고려한 모의실험을 수행하였다. 모의실험 결과 제안된 방안이 위치관리 비용 측면에서 장점이 있음이 확인되었다.