• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.7
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• pp.1293-1310
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• 2011

A simple modification of well known Low Energy Adaptive Clustering Hierarchy (LEACH) protocol is proposed to exploit cooperative diversity. Instead of selecting a single cluster-head, we propose M cluster-heads in each cluster to obtain a diversity of order M. The cluster-heads gather data from all the sensor nodes within the cluster using same technique as LEACH. Cluster-heads transmit gathered data cooperatively towards the destination or higher order cluster-head. We propose a code combining based cooperative diversity protocol which is similar to coded cooperation that maximizes the performance of the proposed cooperative LEACH protocol. The implementation of the proposed cooperative strategy is analyzed. We develop the upper bounds on bit error rate (BER) and frame error rate (FER) for our proposal. Space time block codes (STBC) are also a suitable candidate for our proposal. In this paper, we argue that the STBC performs worse than the code combining cooperation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.755-764
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• 1999

In this study, the system level network simulation is considered with adaptive array antenna in CDMA mobile communication system. A network simulation framework is implemented based on IS-95A/B system to consider dynamic handoff, system level network behavior, and deploying strategy into the overall CDMA mobile communication network under adaptive array algorithm. Its simulation model, such as vector channel model, adaptive beam forming antenna model, handoff model, and power control model, are described in detail with simulation block. In order to maximize SINR of received signal at antenna, maximin algorithm is particularly considered, and it is computed at each simulation snap shot with SINR based power control and handoff algorithm. Graphic user interface in this system level network simulator is also implemented to define the simulation environments and to represent simulation results on real mapping system. This paper also shows some features of simulation framework and simulation results.

• Korean Management Science Review
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• v.28 no.1
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• pp.43-52
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• 2011

The basic objective of broadcast scheduling is to get the smallest length TDMA frame, where many nodes are allowed to transmit simultaneously in a single time slot in a conflict-free manner. The secondary objective is to maximize the number of such transmissions for maximum use of the channel. An Artificial Bee Colony (ABC) with ranking strategy is proposed in this paper for the broadcast scheduling problem. Our proposed method is very efficient for generating initial and neighbor feasible solutions. We can get the best number of time slots and transmission utilization comparing to previous researches.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.425-434
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• 2007

The sponsored search has become significant channel of online advertising, and the large sized advertisers have appeared, so the sponsored search strategy is becoming more important. Since CPC(Cost-per-Click) advertising has different price according to keyword, it is difficult to manage the a lot of keywords at one time. So, the purpose of this study is to investigate the factors which influence on the cost-per-click of sponsored search advertising. That is, there are four factors: impression, CTR(Click through Rate), conversion rate, and keyword's length. for the regression analysis, we use the actual data which is gotten from an ad agency. The result of that, the impression and keyword's length influence cost-per-click positively. However, CTR & conversion rate have no influence on it unexpectedly.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.687-690
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• 2000

본 논문은 IMT-2000 시스템 MAC 계층에서의 채널할당 운용에 관한 것이다. 기존의 2 세대 무선이동통신인 셀룰라나 PCS 에서는 주로 음성이 주요한 트래픽이었기 때문에 채널 할당에 관한 운용전략이 간단했다. 그러나 무선구간 데이터 트래픽의 급속한 증가는 IMT-2000 시스템의 등장을 가져왔고 이 시스템은 음성과 함께 데이터를 전송하기 때문에 2 세대보다 채널할당이 복잡할 수 밖에 없다. 데이터 트래적 중 web 트래픽이 주요한 부분이 될 것은 자명하다. 그래서 본 논문에서는 대상이 되는 트래픽을 web 트래픽으로 한정하고, web 트래픽을 크게 2 개의 class로 구분했다 : streaming & non-streaming 그리고 다시 각각의 class를 2개, 3개의 subclass(type)로 나눴다. 이 구분과 함에 IMT-2000 시스템의 멀티미디어 트래픽 모델링을 사용하여 시뮬레이션을 행했다. 시뮬레이션은 전용채널, 공용채널의 수, type 별 확률을 변화시키면서 여러 가지 상황을 고려해봤다.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.43-51
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• 2004

The purpose of this study was to investigate the present business management strategy of optician's stores for their improvement and development so that they directly related to consumers in the sale channel of eyeglasses are retailing business. For this purpose, it attempted to investigate the present state and business management problem of optical stores in korea. We wish to present problem and improvement direction on optician's stores condition and administration management, and show useful operation method in optician's stores.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.445-446
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• 2012

본 논문에서는 MF-TDMA(Multiple Frequency - Time Division Multiple Access) 방식을 이용하는 위성 시스템의 위성 자원 효율을 높이기 위한 동적 MF-TDMA 프레이밍 기법을 제안한다. DVB-RCS (Digital Video Broadcasting - Return Channel via Satellite)은 감우감쇠를 극복하기 위해 ACM (Adaptive Coding and Modulation) 기법을 사용한다. MF-TDMA에서는 하나의 채널이 동일한 ACM 모드를 지원하기 때문에 사용자의 채널 상태와 요청량을 고려하여 실제로 요구되는 ACM 모드를 지원하는 채널의 수를 계산한다. 모의실험을 통해 채널 상태 변화를 고려하지 않은 정적인 방식에 비해 제안하는 동적인 방식의 위성 자원 효율이 증가한 것을 확인할 수 있었다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.352-354
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• 2011

The performance of multihop cognitive radio networks (CRN) can be improved significantly by using multiple channels in spectrum underlay fashion. However, interference due to the sharing of common radio channel and congestion due to the contention among those flows that share the same links become an obstacle to meet this challenge. How to control efficiently congestion and allocate power optimally to obtain a high end-to-end throughput is a key objective in this work. We reexamined the Network Utility Maximum (NUM) problem with a new primary outage constraint and proposed a novel resource allocation strategy to solve it effectively and efficiently.

• Journal of Distribution Research
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• v.1 no.2
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• pp.141-172
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• 1996

This study is to investigate global logistics strategies of Korean electronics companies. in terms of service parts. According to the survey, Korean electronics companies were pursuing multi-level global logistics network such as global, continental, national, regional and service center echelon for improving the efficiency of service parts global logistics. Especially there was a tendency of developing new continental distribution centers. And the companies were exploiting efficiency through inventory control by multi-level echelon, demand forecasting by the product life cycle and supply and service lead time management. But there were some insufficient factors for the efficiency of global logistics operation at the construction of worldwide real time logistics information system and pursuit of the efficiency on the whole network including subcontractors. For the future competitive advantage of the Korean electronics companies, the following are suggested: 1) the establishment of arranged logistics channel adjusting each company's global strategy, 2) the construction of worldwide real time logistics information system, 3) the reengineering of all logistics procedures such as order processing, shipping, inventory control, etc., 4) the enhancement of the ratio of the supply from the external companies and the internal manufacturing subsidiaries at each continent, 5) and the pursuit of operational internalization of external subcontractors.

• International Commerce and Information Review
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• v.8 no.3
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• pp.277-297
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• 2006

Joined WTO, China has revised or removed continuously some of existing enter barriers which have been protecting Chinese distribution market. Chinese government intend to open completely it's distribution market in 2007. Such as the open policy of Chinese distribution impact on Korean firms which invest in China. in order to occupy China's market, Korean firms needs to prepare counterplan on change of China's distribution environments. China's distribution environment is uncertain on account of remaining communism system even though opening it's distribution market. The purpose of this paper is to suggest diverse counterplan of Korean firms and answer how Korean firms can enter the China's distribution market successfully. through exmaninig how China's distribution channel is formulated and implemented. this study exhibits a model for strategy of Korean firms and shows implementations schemes.