• 한국통신학회논문지
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• 제37A권9호
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• pp.762-771
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• 2012

본 논문은 펨토셀 환경에서 시스템 용량 향상 및 호손율 감소를 위해 펨토 기지국이 자기 최적화 기법을 이용하여 채널별 전송전력을 적응적으로 제어하는 방법을 제안한다. 펨토셀 관련 국제표준에서는 요구사항으로 펨토셀 밀집 배치에 따라 성능 열화가 없어야 한다는 점을 들고 있다. 제안방식에서는 각 펨토 기지국이 펨토 게이트웨이를 통해 전달받은 이웃 기지국의 채널별 전송전력 정보와 주기적 스펙트럼 감지를 통해 측정한 이웃 펨토셀로부터의 채널별 수신 전력을 바탕으로 자신의 채널별 전송전력을 결정하게 된다. 또한 각 채널별로 펨토 사용자 단말(Femto Mobile Station: FMS)의 이동에 따라 적응적으로 전송전력을 제어함으로써, 핸드오버 감소 및 펨토셀 간 균등한 서비스 기회를 가지도록 한다. 이를 통해 펨토셀 밀집 배치에 따른 성능 열화를 방지할 뿐만 아니라, 펨토셀이 밀집할수록 시스템 용량이 향상되고 호손율이 낮아지는 효과를 얻을 수 있다. 또한 채널별 전송전력을 독립적으로 제어함으로써 커버리지 홀을 줄일 수 있으며, 시스템 내에 존재하는 펨토셀의 개수와 상관없이 항상 일정 수준 이상의 커버리지와 호손율을 유지할 수 있다. 컴퓨터 모의실험을 통해 시스템 용량과 호손율 측면에서 기존 방식과 비교 분석하였으며 그 결과 제안한 방식이 기존 방식보다 우수함을 볼 수 있었다.

• 한국정보과학회논문지:시스템및이론
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• 제26권10호
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• pp.1248-1257
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• 1999

MDDS는 디스크 시스템의 성능을 향상시키기 위해 하이퍼큐브의 각 노드에 디스크 블록들을 분산 저장하며, 인접한 노드에서 분산 저장하고 있는 디스크 블록을 중복 저장하고 있는 디스크 시스템이다. 본 논문에서는 디스크 서비스 시간을 분석하기 위한 선행 연구로서 소스 노드에서 생성된 디스크 서비스 요구 메시지가 디스크 서비스를 제공하는 목적 노드에 수신될 때까지의 시간인 전송 시간을 분석한다. 이러한 메시지의 전송 시간을 분석하기 위해 이 메시지가 링크를 통해 전송되지 못하고 대기할 확률인 전송 대기 확률을 분석한다. 이들 메시지의 전송 대기 확률을 분석하기 위해 메시지가 각 링크에서 전송되지 못하고 대기해야 하는 시간인 전송 대기 시간을 분석한다. 또 디스크 서비스 요구 메시지의 전송을 위해 링크가 사용되는 비를 분석하며, 메시지의 전송 대기 확률, 전송 대기 시간, 메시지 전송을 위해 링크가 사용될 비를 이용하여 디스크 서비스 요구 메시지의 전송 시간을 분석한다. Abstract Mirrored Declustering Disk System(MDDS) is the disk system to enhance the performance of disk system for hypercube. In MDDS, each node stores the disk blocks using the declustering technique. And the node also duplicates the disk blocks stored in neighboring nodes. In this paper, as the leading research for analyzing the disk service time, we analyze the transmission time of the disk service request message from the source node to the destination node. To analyze the transmission time of disk service request message, we analyze the probability of blocking the message related to the disk service request. For the analysis of the blocking probability, we analyze the blocking time at the link. We also analyze the rate at which the transmission link is used for transferring the disk service requests. And we analyze the transmission time of disk service request message by using the blocking probability, the blocking time, and the usage rate of link for transmitting the message.

• 전자공학회논문지S
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• 제34S권5호
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• pp.25-34
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• 1997

Relatively slow tuning speed of optical device causes the unwanted delay in high speed single-hop multiwavelength networks. To lessen the overhead, we present a channel access protocol with dynamjic message scheduling. Th eframe structure of proposed protocol adopts hybrid multiaccess scheme in which WDMA is used as a basic multiaccess technique and TDMA is used to provide subchannels within a wavelength band. This architecture has two merits : the network extention is not limited by available number of wavelengths, and the transmission delay caused by optical device tuning time can to minimize the number of tunings. It schedules messages that require same wavelength channels sequencely, so the total transmission delay is reduced by decreasement of wavelength changes. The performance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The peformance of proposed protocol is evaluated through numerical analysis based on probability and queueing theory. The numeric results show that the peformance of proposed protocol is better than that of previous one.

• 대한전기학회논문지:전력기술부문A
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• 제55권7호
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• pp.273-280
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• 2006

This paper suggests the method that forecasts Dynamic Line Rating (DLR). Thermal Overload Risk Probability (TORP) of the next time is forecasted based on the present weather conditions and DLR value by Monte Carlo Simulation (MCS). To model weather elements of transmission line for MCS process, this paper will propose the use of statistical weather models that time series is applied. Also, through the case study, it is confirmed that the forecasted TORP can be utilized as a criterion that decides DLR of next time. In short, proposed method may be used usefully to keep security and reliability of transmission line by forecasting transmission capacity of the next time.

• Journal of Korean Vacuum Science & Technology
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• 제5권1호
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• pp.25-32
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• 2001

Baffles have been used in cryopumps to prevent 300 K thermal radiation from reaching freely cryopanels whose temperature must be kept steadily below certain levels(4 K, 20 K or something) depending on the gas to be pumped. There are two conflicting requirements in designing a baffle such that the transmission of particles(gas molecules) should be maximized, while that of the thermal radiation(photons) minimized. The transmission probability of gas molecules or photons through chevron type baffles, influenced by the detailed geometry of blades, the reflection mode, and the absorption property of the surface, was analyzed parametrically. The effects of geometrical discrepancy between the fabricated baffle and the designed one, resulting in unexpected deterioration in the performance of the baffle, were also investigated by taking into account the gaps(or overlaps) between the baffle blades and the asymmetry in the blade arms.

• Communications for Statistical Applications and Methods
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• 제21권6호
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• pp.487-500
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• 2014

A new method to calculate the transmittable prevalence of an epidemic disease is proposed based on a back-calculation formula. We calculated the probabilities of reactivation and of parasitemia as well as transmittable prevalence (the number of persons with parasitemia in the incubation period) of malaria in South Korea using incidence of 12 years(2001-2012). For this computation, a new probability function of transmittable condition is obtained. The probability of reactivation is estimated by the least squares method for the back-calculated longterm incubation period. The probability of parasitemia is calculated by a convolution of the survival function of the short-term incubation function and the probability of reactivation. Transmittable prevalence is computed by a convolution of the infected numbers and the probabilities of transmission. Confidence intervals are calculated using the parametric bootstrap method. The method proposed is applicable to other epidemic diseases in other countries where incidence and a long incubation period are available. We found the estimated transmittable prevalence in South Korea was concentrated in the summer with 276 cases on a peak at the $31^{st}$ week and with about a 60% reduction in the peak from the naive prevalence. The statistics of transmittable prevalence can be used for malaria prevention programs and to select blood transfusion donors.

• 한국통신학회논문지
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• 제34권7A호
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• pp.530-539
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• 2009

Wireless Relaying is a promising solutions to overcome the channel impairments and provides high data rate coverage that appear for beyond 3G mobile communications. In this paper we present end to end BER performance of dual hop wireless communication systems equipped with multiple Decode and Forward relays over Rayleigh fading channel with the best relay selection. We compare the BER performance of the best relay with the BER performance of single relay. We select the best relay based on the end to end channel conditions. We further calculate the outage probability of the best relay. It is shown that the outage probability of the best relay is equivalent to the outage probability when all relays take part in the transmission. We apply Orthogonal Space Time Block coding(OSTBC) at the source terminal. Numerical and simulation results are presented to verify our analysis.

• Journal of information and communication convergence engineering
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• 제6권2호
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• pp.134-139
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• 2008

In this paper, we propose an analysis model for the performance of channel error probability in Stream Control Transmission Protocol (SCTP) using Markov model. In this model it is assumed that the compressor and decompressor work in Unidirectional Mode. And the average throughput of SCTP protocol is obtained by finding the throughputs of when the initial channel state is good or bad.

• The Journal of the Acoustical Society of Korea
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• 제18권1E호
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• pp.3-6
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• 1999

In digital mobile communication system, the transmission errors affect the quality of output speech seriously. There are many error concealment techniques using a posteriori probability which provides information about any transmitted parameter. They need knowledge about channel transition probability as well as the 1st order Markov transition probability of codec parameters for estimation of transmitted parameters. However, in applications of mobile communication systems, the channel transition probability varies depending on nonstationary channel characteristics. The mismatch of designed channel transition probability of the estimator to actual channel transition probability degrades the performance of the estimator. In this paper, we proposed a new parameter estimator which adapts to the channel characteristics using short time average of maximum a posteriori probabilities(MAPs). The proposed scheme, when applied to the LSP parameter estimation, performed better than the conventional estimator which do not adapt to the channel characteristics.

• 한국정보통신학회논문지
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• 제23권5호
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• pp.589-595
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• 2019

최근 친밀도와 신뢰도 같은 사용자들의 사회적 관계와 모바일 통신 네트워크를 동시에 고려한 모바일 소셜 네트워크가 차세대 이동통신 네트워크 모델로 큰 관심을 받고 있다. 본 논문에서는 사회적 관계 중 신뢰도 정보를 기반으로 하는 협력통신 네트워크를 고려한다. 완벽한 신뢰도 정보를 고려했던 기존 연구들과 다르게 송신단에서 불완전한 신뢰도 정보 기반 정보 처리율 최대화 협력 통신 기법을 제안한다. 본 논문에서는 먼저 불완전한 신뢰도 정보를 확률적인 분포로 모델링하고, 신뢰도의 확률 분포를 이용하여 아웃티지 확률을 유도한다. 마지막으로 송신단에서 아웃티지 확률과 정보 전송율을 동시에 고려한 정보 처리율을 최대화하는 전송 기법을 제안한다. 시뮬레이션 결과를 통해 정보 처리율 관점에서 기존 기법들과의 비교를 통해서 제안한 협력통신 기법의 우수성을 증명한다.