• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.968-980
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• 2008

Providing handover with guaranteed QoS for real-time multimedia service such as VoIP, video/audio streaming, and video conferencing in wireless LAN is a challenging task. In this paper, we present efficient layer 2 handover mechanism in wireless LAN, which can provide fast handover with guaranteed QoS for real-time multimedia service. To this end, the scanning period and the number of channels per scanning for handover are dynamically adapted to the type of applications and wireless networking environment, so that both the degradation of application service quality and signaling overhead are minimized simultaneously. The performance of the proposed mechanism is verified by the simulation. The simulation results show that the proposed mechanism guarantess QoS of each multimedia application with minimal power consumption.

• Journal of KIISE
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• v.44 no.7
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• pp.733-741
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• 2017

LPWAN(Low Power Wide Area Network) technology is M2M (Machine to Machine) networking technology for the Internet of Things. The technology is designed to support low-power, long-distance and low-speed communications that are typical of LoRaWAN(Long Range Wide Area Network). To exchange inter-object information using a LoRaWAN, the link performances for various environments must be known. however, active performance analysis research that is based on an empirical environment is nonexistent. Therefore, this paper empirically evaluates the performance of the LoRa (Long Range) link, a physical communication technology of the LoRaWAN for various variables that may affect the link quality in indoor and outdoor environments. To achieve this, a physical performance monitoring system was designed and implemented. A communication experiment environment was subsequently constructed based on the indoor and outdoor conditions. The SNR(Signal to Noise Ratio), RSSI(Received Signal Strength Indication), and the PDR(Packet Delivery Ratio) were evaluated.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.156-166
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• 2005

Ethernet passive optical network is an economical and efficient access network that has received significant research attention in recent years. A MAC(Media Access Control) protocol of PON, the next generation access network, is based on TDMA(Time Division Multiple Access) basically. In this thesis, we addressed the problem of dynamic bandwidth allocation in QoS based Ethernet PONs. We augmented the bandwidth allocation to support QoS in a differentiated services framework. Our differentiated bandwidth guarantee allocation(DBGA) allocates effectively and fairly bandwidths among end users. Moreover, we showed that DBGA that perform weighted bandwidth allocation for high priority packets result in better performance in terms of average and maximum packet delay, as well as network throughput compared with existing dynamic bandwidth allocations. We used simulation experiments to study the performance and validate the effectiveness of the proposed bandwidth allocations.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.216-225
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• 2004

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels- are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole net-work can be greatly improved.

• Journal of the Korean association of regional geographers
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• v.18 no.2
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• pp.188-202
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• 2012

The purpose of this study is to review a good sample for a healthy city to adapt its strategy. People has interested in the urban environment and their health in the region with a step-up in income and the improvement of living conditions. They has realized that urban environment is closely related to their quality of life, concentrated on development of clean city and healthy city from the point of urban planning. The movement of healthy city has been spread out from Europe on 1986, and WHO(World Health Organization) has been supporting the practical work to improve upon the physical or social condition on each regional level. The policy of healthy city has promoted centering around each local government which is made up of networking with others globally to interchange informations. This study reviewed a successful case of Kobe city in detail and will provide further useful insights into planners in building appropriate policies.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.676-686
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• 2005

The Internet users as well as network providers are eager to have different qualities of service among users beyond the best-effort. In this paper, we propose a scheduling algorithm that provides a differentiated service in the granularity of user sessions. The proposed algorithm is a Hierarchical Deficit Round-Robin (H-DRR) algorithm that is an extension of an existing DRR algorithm. A main advantage is that H-DRR provides service differentiation for throughput-intensive applications such as FTP as well as delay-sensitive applications such as telnet or VoIP without distinguishing the types of applications. The most importance in providing a service differentiation in term of network providers is to have controllability and predictability. We show that H-DRR is superior to DRR in terms of controllability and predictability through both mathematical analysis and simulation experiments. Nevertheless, H-DRR requires O(1) complexity for implementation.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.218-234
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• 2008

중국은 2008년 현재 메신저 이용자 수와 블로그 등의 웹 2.0 이용자 수에 있어서 세계 1위이다. 그리고 중국의 2007년 850억 달러의 인터넷 디지털 시장은 2015년에 2640억 달러로 성장할 전망이다. 이와 같이 인터넷 시장의 규모와 성장 가능성으로 인해 중국 인터넷 비즈니스의 중요성이 높아지고 있다. 이러한 필요성에 따라서 본 연구에서는 중국의 인터넷 동향 중에서 가장 큰 주목을 끌고 있는 웹 2.0 기반의 사회 연결망 서비스 분야에서 다음 세 가지의 연구 질문을 설정하고 그 답을 찾아보았다. 첫째, 중국 사회 연결망 서비스의 주요 특징은 무엇인가? 이러한 질문에 답하기 위해 본 연구에서는 문헌연구를 바탕으로 중국의 대표적인 사회 연결망 서비스 업체로 Tencent QQ와 Sina Poco를 살펴보았고, 중국 사회 연결망 서비스 이용자의 가입 이유, 갱신 이유, 주요 내용, 유상 서비스에 대한 태도 등을 살펴보았으며, 중국 인터넷 사용자의 집단별 특징에 대해 살펴보았다. 둘째, 중국 사회 연결망 서비스의 이용에 영향을 미치는 주요 요인들은 무엇인가? 이러한 질문에 답하기 위해 동기부여이론, TAM 이론. 관련 선행연구 등을 검토하여 중국 사회 연결망 서비스의 이용에 영향을 미치는 요인들로서 사용자 참여, 사회적 영향, 네트워크 효과, 유용성, 시스템 품질 등을 도출하였고 PLS를 이용한 데이터 분석을 통해 검증하였다. 검증결과, 사회 연결망 서비스 이용에 유용성이 가장 큰 영향을 미치고, 다음으로 네트워크 효과, 사용자 참여, 시스템 품질 순으로 유의한 영향을 미치는 것으로 나타났다. 반면, 사회적 영향은 유의하지 않은 것으로 나타났다. 셋째, 중국과 한국은 어떠한 점에서 차이가 있는가? 가장 두드러진 차이는 사회적 영향에 있어서 한국은 유의 적인데 비해 중국이 유의적이지 않다는 점이다. 이는 한국과 중국 사이에 국가 문화적 차이가 존재하기 때문에 발생했다고 생각할 수도 있고, 중국이 인터넷 성장기에 있는데 비해 한국은 인터넷 성숙기에 있는 등의 기술적, 사회적, 경제적 발달 과정상의 차이에 의한 것이라고도 볼 수 있다.

• Korea Journal of Hospital Management
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• v.6 no.2
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• pp.173-201
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• 2001

This study purports to examine the current management and information technology related strategy of Korean hospitals and suggest the effective management strategy in the 21st century when is digital era. Specifically the study tries to analyze the changing trends of strategic orientation and investigate the general management and information technology strategy of Korean hospitals. Self-administered Questionnaires were distributed to 721 hospitals nationwide and finally 98 Questionnaires were analyzed for the study. The results of the study are as follows : 1) Half of the respondent hospitals reported that they have an analyzer orientation in 2000, whereas 19.4% were prospectors, reactors 16.4%, and defenders 14.3%. However, the respondent hospitals intended to have a prospector orientation in the future (2002), while 29.6% planned on being analyzers, 17.3% reactors, and 3.1% defenders. 2) Hospital services for improving patient satisfaction were the most common. strategy for the respondent hospitals, followed by cost containment, organizational restructuring, employee education, purchasing system change, specialization of clinical services, quality improvement of medical care, strengthening the networking with the stakeholders, public relations and marketing strategy, diversification, and installing the information system. However, the strategies of annual salary system, retrenchment of unprofitable services, merit payment based on performance were still not popular for the respondent hospitals. 3) As for the strategies related with information technology, most hospitals have not implemented actively, except for the establishment of home-pages, order communication systems, and insurance claims through electronic data interchange system. 4) There were significant differences in the level of strategy implementation in terms of the ownership, bed size, financial performance, and the top managers I knowledge of information technology. The larger bed size, the higher financial performance, the better knowledge of information technology the top managers have, the more strategies the respondent hospitals implemented. The managerial and political implications for Korean hospitals in digital era were also discussed.

• Journal of Service Research and Studies
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• v.1 no.1
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• pp.49-60
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• 2011

Recently, with the growing of social network sites, people's choice is also getting more and more. So the notion of loyalty has become an important construct within the Social Network framework because of member is easy switching on the social networking sites. Despite the increasing importance of social network sites loyalty question, there's very little research in this area. In electronic commerce, the website loyalty development process is based on both website satisfaction and website trust toward the net-enabled business. But how to target the members with high or low loyalty in the social network sites is still a question. In this paper we propose one improved RFM model to evaluate the member loyalty to find the potential members for improving the service quality of the social network site. In addition, an empirical case study is performed to demonstrate how this procedure works. Moreover, further applications of this research are provided for improved social network sites experiences and how to use the model to practice.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.3
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• pp.99-106
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• 2017

With the increased interest in the quality of life of modern people, the implementation of the five-day working week, the increase in traffic convenience, and the economic and social development, domestic and international travel is becoming commonplace. Furthermore, in the past, there were many cases of purchasing packaged goods of specialized travel agencies. However, as the development of the Internet improved the accessibility of information about the travel area, the tourist is changing the trend to plan the trip such as the choice of the destination. Web services have been introduced to recommend travel destinations and travel routes according to these needs of the customers. Therefore, after reviewing some of the most popular web services today, such as Stubby planner (http://www.stubbyplanner.com) and Earthtory (http://www.earthtory.com), they were supposed to be based on traditional Traveling Salesman Problems (TSPs), and the travel routes recommended by them included some practical limitations. That is, they were not considered important issues in the actual journey, such as the use of various transportation, travel expenses, the number of days, and lodging. Moreover, although to recommend travel destinations, there have been various studies such as using IoT (Internet of Things) technology and the analysis of cyberspatial Big Data on the web and SNS (Social Networking Service), there is little research to support travel routes considering the practical constraints. Therefore, this study proposes a new mathematical model for applying to travel route recommendation service, and it is verified by numerical experiments on travel to Jeju Island and trip to Europe including Germany, France and Czech Republic. It also expects to be able to provide more useful information to tourists in their travel plans through linkage with the services for recommending tourist attractions built in the Internet environment.