• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.285-290
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• 2010

We investigate the outage probability in terms of QoS (quality of service) in indoor PLC network. We consider various kinds of appliances for realistic indoor PLC network. For estimation of the outage probability, we calculate the time-varying channel responses considering the loading conditions based on regular human activities and include the additive noise. We calculate the outage probability for each terminal and investigate relationship between the outage probability and the channel length, and transmit powers. Our results suggest that the outage probability is increased when the channel length becomes longer because more appliances affect the amount of reduced channel capacity and is not improved distinctly for very high and low outage threshold by increasing the transmit power. However, we can see outage probability improvement for 30% outage threshold case by increasing the transmit power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.275-280
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• 2002

Wireless communications have been developed time and time to satisfy more demands of users for internet service, mobile communication service and so on. One of infrastructures leading the next generation wireless communication is HAPS(High Altitude Platform Station). This paper analyzed outage probability when a mobile communication system was constructed by using HAPS. First, an approach to evaluate the carrier to interference power ratio' was introduced and results from the analysis were calculated and simulated. from the results, carrier to interference power ratio (C/I) and fading depth (K) had an effect on outage probability; outage probability decreases when K increases far constant C/I or C/l increases for constant K. In addition, when outage probability for a platform with elevation 30 degrees is expanded into it for 24-platforms, outage probability(C/I=9.8dB) was worse because of many interferers relatively.

• Proceedings of the KIEE Conference
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• summer
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• pp.88-90
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• 2004

Data are a critical utility asset. Collecting correct data on site leads to accurate information. Data, when gathered with foresight & properly formatted, are useful to both existing database and easily transferable to newer, more comprehensive historical outage data. However, when investigating data items options, the task, can be an arduous one, often requiring the efforts of entire committees. This paper firstly discusses the KEPCO's past 10 years of historical outage data which include meterological data, and also by several elements of the National Weather Service, failure rate, outage duration, and probability classification, etc. Then, these collected data are automatically stored in an Outage Data Management System (ODMS), which allows for easy access and display. ODMS has a straight-forward and easy-to-use interface. It lets you to navigate through modules very easily and allows insertion, deletion or editing of data. In particular, this will further provide the KEPCO that not only helps with probabilistic security assessment but also provides a platform for future development of Probability Estimation Program (PEP).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.957-966
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• 1998

In this paper an imrpoved Signal-to-Interference ratio(SIR)-based call admission control(CAC) algorithm for DS-CDMA cellular system is proposed and its performance is analyzed. This algorithm uses Residual-Capacity defined asthe additional number of initial calls that a base station can accept such that system-wide outage probability will guaranteed to remain below a certain level. the residual capcity at each cell is calculated according to the reverse-link SIR measured not only at the home cell but also the adjacent cells. Then the adjacent cell interference-coupling coefficient .betha. is used. In this work we propose an improved algorithm that .betha. varies according to the traffic load of the home cell. The influence of traffic condition on system performance, namely blocking probability and outage probability, is then examined via simulation. The performance of the improved algorithm is evaluated both under homogeneous and hot spot traffic loads. The results show that the improved algorithm outperforms conventional algorithms under all load values. Under over-load situation, especially, the improved algorithm gives almost constant outage performance the QoS(quality of service) can be guranted.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.321_322
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• 2009

최근 전력선 통신이 홈 네트워킹의 새로운 기술로 주목을 받고 있어 관련 수요가 증가하고 있다. 안정적인 통신을 위하여 일정한 QoS(Quality of Service)의 제공은 매우 중요하다. 본 논문에서는 outage 확률 분석을 위하여 시뮬레이션을 이용한 옥내 전력선 통신 환경에 대한 채널 응답과 채널 용량을 계산하였다. 계산된 채널 응답과 채널 용량을 바탕으로 전송 신호의 파워에 따른 outage 확률을 분석을 하였다. 시뮬레이션 분석 결과 아주 높은 수준과 아주 낮은 수준의 QoS 환경에서 전송 신호의 파워는 outage 확률에 영향을 미치지 않았다. 하지만, 30% ~ 50% outage를 허용하는 QoS 환경에서는 전송 신호의 파워에 따라서 outage 확률이 상대적으로 크게 변화하였다. 따라서 본 논문에서는 outage 확률측면에서 전송 신호의 파워를 효율적으로 이용할 수 있는 방향을 제시한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.338-347
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• 2012

In this paper, we propose the cooperative transmission scheme (CTS) for system throughput maximization in OFDMA based enterprise femtocell networks. In our scheme, the user equipment (UE) can receive the desired signal from serving femtocell BS (fBS) as well as an adjacent fBS. Thus, UE achieves an improved signal to interference plus and noise ratio (SINR) by the synchronized two signals. The performances of this strategy consider not only the call-level quality of service (QoS) but also the packet-level QoS. We first measure the call blocking probability and utilization for the downlink resources for various offered load in femtocell. Based on that, the outage probability and effective throughput of the system are simulated. Simulation results show that the proposed scheme can reduce the outage probability for enterprise femtocell compared with conventional systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1844-1851
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• 1999

In this paper, we propose an effective access control scheme based on service characteristics to provide multimedia services such as voice, video and data in broadband CDMA networks. In proposed algorithm, BER characteristics of each service is controlled by different Eb/No, and data traffic is controlled by access probability of data which is determined by activity factor of voice/video traffic. And we perform simulation and analysis of proposed model. As a result, the proposed access scheme shows that the outage probability is decreased by allowing delay of data traffic.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2455-2472
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• 2012

Although underlay spectrum sharing has been shown as a promising technique to promote the spectrum utilization in cognitive radio networks (CRNs), it may suffer bad secondary performance due to the strict power constraints imposed at secondary systems and the interference from primary systems. In this paper, we propose a two-phase based cooperative transmission protocol with the interference cancellation (IC) and best-relay selection to improve the secondary performance in underlay models under stringent power constraints while ensuring the primary quality-of-service (QoS). In the proposed protocol, IC is employed at both the secondary relays and the secondary destination, where the IC-based best-relay selection and cooperative relaying schemes are well developed to reduce the interference from primary systems. The closed-form expression of secondary outage probability is derived for the proposed protocol over Rayleigh fading channels. Simulation results show that, with a guaranteed primary outage probability, the proposed protocol can achieve not only lower secondary outage probability but also higher secondary diversity order than the traditional underlay case.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.245-246
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• 2008

A cell planning and resource allocation scheme called the proposed is presented for improving channel capacity and for maintaining a proper QoS (Quality of Service) over the downlink OFDMA (Orthogonal Frequency Division Multiple Access) system. Through an optimal combination of sectorization and frequency overlay, the proposed scheme accomplishes an improvement in both channel capacity and outage probability. In the simulation, the proposed scheme outperforms 3-sectorization in terms of throughput and outage probability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.720-726
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• 2008

In this paper, we propose a multi-cell cooperation method for broadcast packet data services in the orthogonal frequency division multiplexing (OFDM)-based cellular system with multiple transmit antennas. In the proposed method, to transmit two streams of spatially demultiplexed or transmit diversity coded symbols over a number of transmit antennas, we divide a coded packet into multiple subparts to which different cell groups and antenna pairs are assigned. The proposed method enhances the diversity order by transforming the channel frequency responses of two symbol streams in each subpart of the broadcast packet. The increase in diversity of the proposed method is shown with the outage probability under various configurations.