• 한국IT서비스학회지
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• 제9권2호
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• pp.163-177
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• 2010

In this paper, we consider a channel ordering problem that seeks to maximize the service quality in mobile radio communication systems. If a base station receives a connection request from a mobile user, one of the empty channels belonging to the base station is assigned to the mobile user. In case multiple empty channels are available, we can choose one that incurs least interference with other channels assigned to adjacent base stations. However, note that a pair of channels that are not separated enough generates interference only if both channels are assigned to mobile users. That is, interference between channels may vary depending on the channel assignment sequence for each base station and on the distribution of mobile users. To find a channel assignment sequence that seems to generate minimum interference, we develop an optimization model considering various scenarios of mobile user distribution. Simulation results show that channel assignment sequence determined by the scenario based optimization model significantly reduces the interference provided that scenarios and interference cost are properly generated.

• 한국통신학회논문지
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• 제36권9A호
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• pp.767-775
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• 2011

본 논문에서는 IEEE 802.16n 기반 단말간 직접통신을 위한 MIMO (multi-input multi-output) 채널 모델링 기법을 제안한다. 송신단과 수신단에 모두 이동성을 반영하기 위하여 기하학적 이중링 산란 환경을 적용하고 기존 802.16m에서 사용하는 채널 모델링 방식을 단말간 직접통신에 적합하도록 변형하여 새로운 채널 모델을 제안한다. 모의실험을 통해 시간영역 및 공간영역에서 제안된 채널 모델의 통계적 특성을 분석하고, 모의실험을 통해 기존 802.16m 기지국-단말간 채널 모델에서의 링크 성능과 제안된 채널 모델에서의 링크 성능을 비교한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1451-1454
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• 2002

In recent years, there are growing concerns about land mobile satellite (LMS) communication systems and mobile stratospheric communication systems (SCS) for the purpose of service upgrade of personal and mobile communications in near future. It is important to possess accurate channel model for prediction of the above system performance. Thus, in this paper, we evaluate the bit error rates of a coded BPSK system based on realistic channel model which can be applied to stratospheric communication systems. The channel data was made by fitting the parameters of probability distribution model to measured data. This approach was proposed by Corraza〔1〕and modified by You〔2〕. And also the effects of channel codings on the system performance are analyzed. As results, we can get the performance curve characteristics on realistic Rician log-normal fading channels with various communication environments.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.288-300
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• 2006

In this paper, we consider a channel ordering problem that seeks to minimize the total interference in mobile radio networks. If a base station receives connection request from a mobile user, one of the empty channels that are fixed to the base station is assigned to the mobile user. Among several channels available, we can choose one that seems to make least interference with other channels assigned to adjacent base stations. However, a pair of channels that are not separated enough do not generate interference if both of them are not simultaneously used by mobile users. That is, interference between channels may vary depending on the channel assignment sequence for each base station and on the distribution of mobile users. To find a channel assignment sequence that seems to generate minimum interference, we develop an optimization model considering various scenarios of mobile user distribution. Simulation results show that channel assignment sequence determined by the scenario based optimization model significantly reduces the interference provided that scenarios and interference costs are properly generated.

• The Journal of the Acoustical Society of Korea
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• 제28권3E호
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• pp.99-108
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• 2009

In this paper, we suggest criteria for objective measurement of speech quality in mobile VoIP (Voice over Internet Protocol) services over wireless mobile internet such as mobile WiMAX networks. This is the case that voice communication service is available under other networks. When mobile VoIP service users in the mobile internet network based on packet call up PSTN and mobile network users, but there have not been relevant quality indexes and quality standards for evaluating speech quality of mobile VoIP. In addition, there are many factors influencing on the speech quality in packet network. Especially, if the degraded speech with packet loss transfers to the other network users through the handover, voice communication quality is significantly deteriorated by the transformation of speech codecs. In this paper, we eventually adopt the Gilbert-Elliot channel model to characterize packet network and assess the voice quality through the objective speech quality method of ITU-T P. 862. 1 MOS-LQO for the various call scenario from mobile VoIP service user to PSTN and mobile network users under various packet loss rates in the transmission channel environments. Our simulation results show that transformation of speech codecs results in the degraded speech quality for different transmission channel environments when mobile VoIP service users call up PSTN and mobile network users.

• 한국경영과학회지
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• 제34권4호
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• pp.185-204
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• 2009

The USIM(universal subscriber identity module)-unlock introducing in July 1, 2008 might be led to a significant change that mobile service provider's dominance is considerably dispersed to the handset manufacturer and distributor. Under USIM-unlock environment, mobile service provider, handset manufacturer, and distributor have to make their decisions on their handset distribution channel strategies: the closed distribution channel strategy or the open distribution channel strategy. The change of distribution channel strategy between members in distribution channel can be understood as a matter of strategy choice, and we have developed a theoretical model and analyzed how to make a decision for the member's optimal distribution strategy based on 3-person game model between members of mobile phone distribution channel, under both of '1 subscriber-1 handset' and '1 subscriber-multiple handset' assumptions. Under '1 subscriber-1 handset' assumption, the closed strategy controlled by mobile service provider is all players' optimal solution because the maximum size of the mobile phone market is limited by subscribers. But, as total expected profit by the handset and distribution subsides is a deficit, mobile service provider have to choose the open strategy and consider the conversion to MNO(mobile network operator). Under '1 subscriber-multiple handset' assumption, mobile service provider is trying to find the way how to lock-in its service and mobile phone and how to maximize ARPU(average revenue per unit), while handset manufacturer and distributor have to look for the way how to maximize the mobile phone market using their own marketing efforts, because it is expected that total mobile handset demand for the open market is bigger than demand for the closed market under '1 subscriber-multiple handset' assumption.

• 한국시뮬레이션학회논문지
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• 제10권4호
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• pp.11-20
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• 2001

In the IMT-2000 networks, the model of micro/pico cell is suggested for transmission of multimedia service. Hence, the efficient method is required for processing of mobile calls in micro/pico cell. In the central urban area, mobile calls may be dynamically increased because of many mobile users. And microcel]/picocell size has small size, handover calls will be more increased. Therefore, many of mobile calls is occurred at a cell in the central urban area, so channel requests for these calls will be increased in the call. In this paper, we propose a scheme, FTC(Fault Tolerant Channel allocation) which is the channel management method for hard handover and new call in a mobile cell of central urban area. When available channels in the cell are consumed, the FTC investigates channel states of neighbor cells in the RNC(Radio Network Controller) or BSC (Base Station Center), and provide available channel for mobile call. The ]no scheme is analyzed and compared with existing channel management method by simulation.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3775-3781
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• 2009

본 연구의 목적은 모바일 상거래의 채널만족과 채널선호에 영향을 미치는 요인을 분석하는 것이다. 기술수용모형, 거래비용이론 그리고 서비스 품질에 대한 이론적 배경을 바탕으로 연구모형을 설정하였으며, 모바일 사용자 320명을 대상으로 AMOS 7.0 통계패키지를 이용하여 실증연구를 수행하였다. 연구결과, 유용성, 자산특유성, 불확실성, 신뢰, 응답성이 채널만족에 유의한 영향을 미쳤으며, 채널만족이 채널선호에 유의한 영향을 미치는 것으로 나타났다.

• Journal of Information Technology Applications and Management
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• 제28권1호
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• pp.111-121
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• 2021

The growth of online malls encourages the existing offline stores to manage their online stores or reinforce the purchasing service through related mobile applications (apps). This may seem to be the omni-channel strategy for connecting the existing customers to online shopping. This study, research on offline stores' acceptance of and satisfaction with smart phone apps, attempted to arrange some factors allowing consumers to be satisfied with such apps, and examine whether the satisfaction with the apps lead to that with the stores based on the EMTAM (Extended Mobile Technology Acceptance Model). In particular, the existing stores trying to enhance the omni-channel put on emphasis on the synergy between online and offline stores, rather than replace offline store with online ones. The results of an analysis showed that the factors influencing the satisfaction with apps included mobile usefulness (MU), mobile ease of use (MEOU) and mobile enjoyment (MEJ), and that the satisfaction with them had an effect on that with stores. On the basis of the findings, this study summarizes theoretical and practical suggestions.

• 전자공학회논문지 IE
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• 제44권4호
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• pp.41-47
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• 2007

본 논문에서 이동 대 이동 Rayleigh 및 Rician 페이딩 채널 상에서 시뮬레이션 모델의 성능이 분석되고 그 결과가 비교된다. Clarke의 페이딩 모델의 수신 신호 및 Clarke의 페이딩 모델에서 위상 천이된 수신 신호에 근거한 자기 상관 함수 및 상호 상관 함수를 유도하고, 그 시뮬레이션 모델의 결과를 구하였다. 또한 이동 대 이동 Rician 페이딩 채널에 이 두 모델을 적용하고, 복소 포락선 수신 신호의 자기 상관 함수 결과는 통계적 특성이 이론값과 매우 일치하고, N=8인 작은 수에서도 빨리 수렴함을 보였다.