• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.415-424
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• 2008

In this paper, we compare the QoS performance enhancement schemes according to the network architecture of mobile WiMAX system in order to improve the end-to-end QoS performance and propose QoS parameter mapping method and IP packet scheduling algorithm. To evaluate the end-to-end QoS performance, we implemented an end-to-end simulator of mobile WiMAX system using OPNET. Simulation results show that the proposed QoS parameter mapping scheme reduces the average delay of VoIP packet and improves uplink resource efficiency. And also, when the proposed IP packet scheduling algorithm is applied to the system, the end-to-end packet transmission delay of VoIP service can be reduced by 44-67 percent compared to FIFO and WRR scheduler.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.12a
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• pp.411-419
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• 1999

EBPP는 소비자, 사업자간에 고지서 발송, 접수 및 지불을 네트워크를 통하여 전자적으로 처리하는데 필요한 환경을 의미하며, 인터넷을 기반으로 하여 전자우편 혹은 웹 페이지를 통하여 고지서를 처리한다 EBPP 시스템은 크게 소비자, 사업자 그리고 은행간의 거래로 이루어 지지만 컴퓨터 및 인터넷의 보급의 한계 등의 문제로 현재로서 모든 고지서를 전자적으로 처리하는 것은 무리가 따른다. 그럼에도 불구하고 EBPP 시스템은 1) 경쟁력 확보를 위해 기업/금융 기관들이 인터넷을 통한 고품질 서비스 개발에 주력하는 추세이고, 2) 고객과의 보다 긴밀한 관계 유지를 위한 수단 제공하며, 3) 인터넷 등 온라인 통신 인구가 급격한 증가(2701년에 전체 인구의 약 50%가 활용할 것으로 전망)하고 있으며,4) 소비자를게 보다 편리한 지불방법 제시해주며, 5) 또 다른 마케팅 매체로 활용 가능하므로 앞으로의 전망이 매우 밝다. EBPP시스템은 크게 금융기관, 기업, 소비자 부분으로 구성되며, 소비자와 접촉 방법으로는 대표적으로 Web과 전자우편을 생각할 수 있으며, EBPP 시스템을 구축하기 위해서는 기본적으로 상접 혹은 기업에서 청구에 필요한 정보를 등록시키는 통합 청구서버(Bill consolidation server), 소비자에게 청구 가능한 정보를 갖고있는 청구 제시서버 (Bill presentment server), 소비자의 지불요청에 따라 은행으로부터 지불을 요구하는 지불서버(Payment gateway) 등이 필요하며, 이들 각각의 서버들의 구성 요소들은 제공하는 서비스에 따라 달라질 수 있다. 통합 청구서버에서 청구 제시서버로 전송되는 청구 건은 통상적으로 실시간 처리되는 것이 아니라 통합 청구서버에 존재하는 Spool DB에 저장되어 그 양이 일정한도를 넘어서면 자동 전송되도록 하여, 망의 할용도를 높이는 역할을 수행한다. 청구 제시서버의 DB에 등록된 청구 건은 인터넷을 통해 소비자에게 청구되며, 소비자에게 전송 되는 청구서는 사용자DB를 참조하여 사용자가 미리 정의한 원하는 형태로 변환되어 전달되며, 필요시 암호화 과정을 거치는 것이 가능해야 한다. 전송된 청구서는 전자우편의 경우, 암호해독이 가능한 전용 브라우저를 통해 열람 되며, 이는 다시 전용 브라우저를 통해 지불인증이 승인되어 청구 제시서버에게 전송된다. EBPP 시스템의 제어 흐름은 크게 기업이 청구 정보를 소비자에게 제시하는 흐름과 소비자의 지불 승인으로 인해 기업이 은행에 지불을 요구하는 흐름으로 구분할 수 있다. 본 논문에서는 통합 청구서버 및 정구 제시서버의 역할 및 구성 요소들에 대해 서술하고, EBPP 시스템과 연동하여야 하는 메일 서버와의 상호 작용에 대해 서술할 것이다. 본 시스템을 아직 구현이 되지 않은 관계로 시스템의 성능 등의 수치적 결과를 제시할 수 없는 상태다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1252-1263
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• 2009

In this paper, in order to improve a service quality and to broaden the service coverage in the mobile communication system a study on a digital RF repeater employed with an Interference Cancellation System(ICS) is performed. The digital RF repeater employed with an ICS is implemented to remove interference and feedback signals which are disadvantages of a conventional(or general) RF repeater. This thesis presents the design and experiments of the new wireless repeater. The proposed wireless repeater consists of a RF repeater mounted with digital engine. The digital ICS engine consists of a DSP and FPGA. The digital engine and RF circuit are designed into a one-piece. After developing hardware through the digital platform they are also designed and fabricated into a one-piece in order to apply a best performance repeater system. The method of removing interference and feedback signals is an adaptive IF technique employed with a LMS algorithm. The powerful performance and fast convergence speed is obtained by using this method.

• KIISE Transactions on Computing Practices
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• v.20 no.12
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• pp.688-693
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• 2014

With the advent of ubiquitous environments, the smart phone has come into wide use and the demand for various content increases. Thus, in order to efficiently utilize limited resources cognitive radio technology is regarded as a possible solution. Besides spectrum sensing or access schemes, the provision of VoIP traffic service for secondary users with limited spectrum resources is a very important issue. In this paper, a resource allocation and control system for VoIP QoS provision in cognitive radio networks is proposed. Firstly, as the system model, the time structure of the network is addressed and, according to the structure, a bandwidth broker is proposed. In addition, based on available bandwidth estimated by the bandwidth broker, a connection admission control for secondary users is developed. It is demonstrated that the provision of VoIP QoS is greatly affected by channel utilization, the number of channels, and the length of timeslot.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.535-544
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• 2018

As the spread of mobile devices equipped with various sensors and high-quality wireless network communications functionsexpands, the amount of spatio-temporal data generated from mobile devices in various service fields is rapidly increasing. In conventional research into processing a large amount of real-time spatio-temporal streams, it is very difficult to apply a Hadoop-based spatial big data system, designed to be a batch processing platform, to a real-time service for spatio-temporal data streams. This paper extends the MapReduce online framework to support real-time query processing for continuous-input, spatio-temporal data streams, and proposes a load management method to distribute overloads for efficient query processing. The proposed scheme shows a dynamic load balancing method for the nodes based on the inflow rate and the load factor of the input data based on the space partition. Experiments show that it is possible to support efficient query processing by distributing the spatial data stream in the corresponding area to the shared resources when load management in a specific area is required.

• Journal of the Korean Regional Science Association
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• v.35 no.3
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• pp.33-44
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• 2019

Smart City is the regional innovation platform that actively utilizes information and communication technologies to diversify city services and improve the performance and quality, hence improving the quality of life and creating new trends of urban activities. Recently, the importance of citizen participation is increasingly emphasized to build smart cities successfully and the Living Lab, an open innovation platform led by users, is taking center stage as a means of realizing it. Accordingly, this study aims to establish the plans for popularizing living labs that provide innovative environments for domestic smart cities. To this end, first of all, political trends related to domestic smart cities' living labs were analyzed, and then, individual characteristics and development processes of the relevant cases were investigated. In addition, in-depth interviews were conducted with the experts of specialized agencies from Netherlands, Finland, and Denmark, etc. which are considered as leading countries in smart cities' living labs. As a result, in order to popularize living labs in domestic smart cities, the following policies were proposed; establishing support systems for commercialization and dissemination, building intermediary support organizations, improvement of laws and institutions, establishing the joint response systems with neighboring areas, etc.

• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.595-604
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• 2004

By the help of expansion of computer network and rapid growth of Internet, the information infrastructure is now able to provide a wide range of services. Especially open architecture - the inherent nature of Internet - has not only got in the way of offering QoS service, managing networks, but also made the users vulnerable to both the threat of backing and the issue of information leak. Thus, people recognized the importance of both taking active, prompt and real-time action against intrusion threat, and at the same time, analyzing the similar patterns of in-trusion already known. There are now many researches underway on Intrusion Detection System(IDS). The paper carries research on the in-trusion detection system which hired supervised learning algorithm and Fuzzy membership function especially with Neuro-Fuzzy model in order to improve its performance. It modifies tansigmoid transfer function of Neural Networks into fuzzy membership function, so that it can reduce the uncertainty of anomaly intrusion detection. Finally, the fuzzy logic suggested here has been applied to a network-based anomaly intrusion detection system, tested against intrusion data offered by DARPA 2000 Intrusion Data Sets, and proven that it overcomes the shortcomings that Anomaly Intrusion Detection usually has.

• Journal of Internet Computing and Services
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• v.8 no.2
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• pp.55-65
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• 2007

BcN is a high-quality broadband network for multimedia services integrating telecommunication, broadcasting, and Internet seamlessly at anywhere, anytime, and using any device. BcN is Particularly vulnerable to intrusion because it merges various traditional networks, wired, wireless and data networks. Because of this, one of the most important aspects in BcN is security in terms of reliability. So, in this paper, we suggest the sharing mechanism of security data among various service networks on the BcN. This distributed, hierarchical architecture enables BcN to be robust of attacks and failures, controls data traffic going in and out the backbone core through IP edge routers integrated with IDRS. Our proposed anomaly detection scheme on IDRS for BcN service also improves detection rate compared to the previous conventional approaches.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.259-274
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• 2005

In this paper, we propose a methodology to estimate the number of users in e-Commerce systems. There have been a lot of previous work under the closed-LAN system environment. But the study on the number of acceptable users in real network environment is hard to find in the literature. Our research applies a Hybrid Simulation by using QoS results for end-to-end high-speed Internet service, and experiments are performed with regard to LAN and WAN, network equipments, and various network bandwidth. As result of the experiments we observed that the response time of high-speed Internet service media(Wireless LAN, ADSL, Cable, VDSL) depends heavily on the sequence and depth of transactions and on the ratio of transactional and non-transactional interactions. That is, as the network and application get more loads, the number of acceptable users decreases. By adding a cache server and an L4 switch to the simulation model, we analysed the changes in the number of users and client response time.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.11
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• pp.409-418
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• 2014

The amount of data located in storage servers has dramatically increased with the growth in cloud and social networking services. Storage systems with very large capacities may suffer from poor reliability and long latency, problems which can be addressed by the use of a hybrid disk, in which mechanical and flash memory storage are combined. The Linux-based SSD(solid-state disk) uses a caching technique based on the DM-cache utility. We assess the limitations of DM-cache by evaluating its performance in diverse environments, and identify problems with the caching policy that it operates in response to various commands. This policy is effective in reducing latency when Linux is running in native mode; but when Linux is installed as a guest operating systems on a virtual machine, the overhead incurred by caching actually reduces performance.