• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(D)
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• pp.187-189
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• 2012

The medium access control (MAC) protocol is designed only for single channel in the IEEE 802.11 standard. That means the throughput of the network is limited by the bandwidth of the single channel. The multiple channels can be exploited to get more concurrent transmission. In this paper, we propose a novel Multi-channel MAC that utilizes the channel more efficiently than other Multi-channel MAC protocols.

• 한국통신학회논문지
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• 제35권1C호
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• pp.45-54
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• 2010

이 논문에서는 다중사용자 (multi-user) 다중안테나 (multiple-in multiple-out : MIMO) 시스템을 위한 전송기법을 제안한다. Costa가 증명한 더티페이퍼코딩 (dirty-paper coding: DPC)이론에 따르면 송신기가 수신기의 가우시안 분포를 갖는 간섭 신호를 알고 있는 경우 간섭 신호에 상관 없이 채널 캐패시티를 얻을 수 있음이 알려져 있다. 단독사용자 채널의 경우 간단하며 효율적인 DPC기법들이 알려져 있으나 다중사용자 환경에는 실제 구현하는데 있어 복잡도와 관련해 많은 문제를 가지고 있다. 이 논문에서 우리는 다중사용자 환경에서 송신기에 알려진 갑선신호를 효율적으로 제어할 수 있는 네트워크 채널 행렬 삼각화 (network channel matrix triangulation: NMT)기법을 제안하고자 한다. 제안하는 NMT 알고리즘은 다중사용자 MIMO 채널을 서로 독립된 병렬의 Single-input Single-output (SISO) 채널들로 변환하여 단독사용자 환경을 위해 제안되어 있는 기존 DPC기법들을 다중사용자 환경에서도 사용 가능케 한다. 시뮬레이션 결과를 통해 제안된 알고리즘이 다중사용자 환경의 채널 캐패시티에 거의 접근함을 보일 것이다.

• Journal of Communications and Networks
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• 제15권1호
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

• 방송공학회논문지
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• 제7권2호
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• pp.88-95
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• 2002

최근 방송의 디지털화에 따라 지상파, 위성 등의 방송 매체는 다채널 서비스가 가능하게 되었고, CATV 및 위성에서는 수백 채널의 수용이 가능하게 되었다. 이에 따라 시청자의 채널에 대한 선택의 폭이 넓어지게 되었으나 수백 개의 채널중 시청자의 취향에 맞는 채널을 선택한다는 것은 어려운 일이다. 이에 본 논문에서는 Set Top Box(STB)와 같은 다채널 방송 수신 장치에서 자동적으로 개인의 취향에 맞는 방송 프로그램을 추천해 주기 위한 효과적인 방법을 제시한다. 사용자가 시청한 프로그램에 대한 정보를 MPEG-7 MDS를 이용해 user history data로 작성하고, 이 user history data를 이용해서 시간대별 사용자의 취향과 유사한 장르의 프로그램을 추천하고, 추천된 장르에서의 채널 선호도를 고려하여 채널을 선택한다. 실험한 결과에 따라 본 논문에서 제안하는 방법이 사용자 취항의 채널을 선택하는데 효과적임을 알 수 있다.

• 한국의류산업학회지
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• 제16권5호
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• pp.730-744
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• 2014

With advances in QR code, mobile is becoming one of important channels in the fashion retail industries. This study attempts to understand the importance of QR code utilization in creating multi-channel business model. Study objectives are to classify types of multi-channel retailing by QR code utilization and to explore the role of QR code technology in strategic marketing elements for types of multichannel retailer. As an exploratory approach, a total of 78 news articles regarding QR code issues were reviewed and analyzed by focusing on 48retailers seleted in this study. The results found seven dimensions of QR code marketing strategies: abundant product information, additional information contents, transaction accessibility, connectedness to channels, location based service, loyalty program and multimedia advertising. Based a combination of channels and level of mobile apps' activation, multichannel retailers utilizing QR code technology were classified into four types; bricks-click-active mobile model, bricks-click-inactive mobile model, bricks-click model, and click-active mobile model. There were differences of using QR code marketing strategies among multichannel models. According to results, for bricks-and-mortar retailers, QR code was critical to integrate shopping experience with merchandise or sales promotions across channels. In addition, for non-store retailers, the QR code utilization was successful in expanding mobile channels, which can promote retail sales by a two-way interaction with customers via the mobile apps.

• 한국유통학회지:유통연구
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• 제13권3호
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• pp.27-54
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• 2008

본 연구는 가정 내 유통업체(In-home shopping channel)의 다채널 고객관리에 시사점을 제공하기 위하여 가정 내 쇼핑채널로서 TV, 카탈로그 및 인터넷 쇼핑채널 간 소비자의 정보탐색과 구매행동과의 관계를 고찰하였다. 가정 내 쇼핑채널들의 정보탐색과 구매행동과의 관련성을 채널 내 고객 고정(channel lock-in)과 채널 간 시너지(cross-channel synergy)로 구분하여 영향력을 비교 평가하였다. 이를 위하여 1개월 동안의 가정 내 쇼핑채널 이용에 대한 자료를 345명의 가정주부를 대상으로 수집하였다. 소비자의 구매채널 이용행동을 선택, 빈도 및 지출행동으로 구분하여 분석을 수행만 결과 가정 내 쇼핑채널 간 정보탐색과 구매행동 간에는 높은 채널 내 고객 고정 효과가 나타나고 있으며 낮은 채널 간 시너지 효과가 나타나고 있었다. 또한 TV 채널의 경우 카탈로그와 인터넷 채널 간 대체성이 나타나는 반면에 카탈로그와 인터넷 채널은 보완성이 나타나고 있다. 이러만 결과는 가정내 다채널 유통기업에게 채널 간 조정과 통합 및 고객관리에 많은 시사점을 제공하고 있다.

• 한국가시화정보학회지
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• 제19권2호
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• pp.63-73
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• 2021

It is essential to accurately predict the change in water level, velocity, and flow rate for each passage of the grit chamber according to the operating conditions of the pump. In this study, VOF multiphase flow analysis was performed, and the flow characteristics of the grit chamber were predicted. As a result of simulations, the sedimentation phenomenon after the entrance of the grit chamber channel is expected to occur on the side walls. When 6 channels are used, the average speed of the channels is about 52% of the design standard, and when 4 channels are used, the value increases to 74% of the design standard. The average water level in the channels tends to decrease as the flow velocity increases, and the water level in the absorption well with a larger flow rate is maintained lower than that in the absorption well with a smaller flow rate.

• 한국ITS학회 논문지
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• 제12권3호
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• pp.87-95
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• 2013

본 논문에서는 다중 홉 시스템에서 하나의 홉에 대한 채널 정보만을 이용하는 효율적인 부분 중계 노드 선택(efficient partial relay selection, EPRS) 기법에 대한 아웃티지 확률을 레일레이 페이딩 채널에서 분석한다. 특히, 디코딩 후 전달 중계 기반의 EPRS 기법에 대한 정확한 아웃티지 확률의 식을 유도한다. 또한, 다중 홉 시스템에서 EPRS 기법의 실효성을 확인하기 위하여, 임의의 중계 경로에서 종단간 신호 대 잡음비와 각 홉의 신호 대 잡음비의 상관관계를 분석한다. 그리고, 수치적 결과를 통해 EPRS 기법과 모든 채널 정보를 이용하는 중계 노드 선택 기법의 아웃티지 성능을 비교한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권2호
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• pp.629-648
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• 2012

Given a video stream delivering system deployed on a multicast tree, which is embedded in a multi-channel multi-radio wireless mesh network, our problem is concerned about how to allocate interference-free channels to tree links and maximize the number of serviced mesh clients at the same time. In this paper, we propose a channel allocation heuristic algorithm based on best-first search and backtracking techniques. The experimental results show that our BFB based CA algorithm outperforms previous methods such as DFS and BFS based CA methods. This superiority is due to the backtracking technique used in BFB approach. It allows previous channel-allocated links to have feasibility to select the other eligible channels when no conflict-free channel can be found for the current link during the CA process. In addition to that, we also propose a tree refinement method to enhance the quality of channel-allocated trees by adding uncovered destinations at the cost of deletion of some covered destinations. Our aim of this refinement is to increase the number of serviced mesh clients. According to our simulation results, it is proved to be an effective method for improving multicast trees produced by BFB, BFS and DFS CA algorithms.

• 산업경영시스템학회지
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• 제29권4호
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• pp.100-106
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• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.