• 한국전산구조공학회논문집
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• 제32권3호
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• pp.173-181
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• 2019

제한된 실험 데이터로부터 확률분포함수를 추정하기 위해서 KDE가 많이 사용되고 있다. KDE에 의한 분포함수는 대역폭 선택법에 따라서 실험 데이터에 대해 평활하거나 과대적합된 커널 추정치를 생성한다. 본 연구에서는 Silverman's rule of thumb, rule using adaptive estimate, oversmoothing rule을 사용해서 각 방법에 따른 정확성과 보수적인 성향을 비교하였다. 비교를 위해서 단봉분포와 다봉분포를 가지는 실제 모델을 가정하고 통계적 시뮬레이션을 수행한 다음 다양한 데이터의 개수에 따른 추정된 분포함수의 정확도와 보수성을 비교하였다. 또한, 간단한 신뢰성 예제를 통해 대역폭 선택법에 따른 KDE의 추정된 분포가 신뢰성 해석 결과에 어떻게 영향을 미치는지 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제15권3호
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• pp.275-280
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• 1994

In the case of the image reconstruction from unknown projection data such as imaging the object with opaque obstructions, conventional reconstruction algorithms may reconstruct a degraded image. In this paper, a new method for the estimation of the unknown projection data based on known projection data and the bandwidth of projection data is proposed. The proposed method successfully estimates the unknown projection data through iterative transformation between projection space and frequency space using the known projection data and the bandwidth of the projection data. Computer simulation shows that the proposed method significantly improves image quality and convergence behavior over conventional algorithms. In addition, the proposed method is successfully applied to ultrasound attenuation CT using a sponge phantom.

• 조명전기설비학회논문지
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• 제21권4호
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• pp.104-114
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• 2007

In this paper, an Ad-hoc Routing Protocol that works in wireless Ad-hoc communication networks with multiple radios and multiple channels and that controls call admission based on bandwidth measurement is proposed. Unlike the conventional Ad-hoc node with a single radio using a single channel, an Ad-hoc node of the protocol proposed, the MCQosR(Multiple Channel Quality of Service Routing), has multiple radios and uses multiple channels, which allows full duplex transmission between wireless Ad-hoc nodes, and reduces intra interference on the route. Also, a fixed channel only for reception at each node enables the estimation of the available bandwidth, which is used to control the call admission for QoS provision. The performance of the MCQosR was verified by simulation.

• 인터넷정보학회논문지
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• 제9권6호
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• pp.179-188
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• 2008

무선망에서 TCP의 성능을 증대시키기 위한 많은 연구가 진행되어 왔지만 패킷 손실률이 큰 경우, TCP의 성능은 아직도 개선의 여지가 많다. 본 논문은 무선 TCP의 한 종류인 TCP Westwood에서 랜덤 패킷 손실률이 높을 때 성능이 저하되는 문제를 지적하고 그 원인을 분석하였다. TCP Westwood의 성능 저하는 랜덤 패킷 손실률이 증가할수록, TCP Westwood의 가용 대역폭 측정(Available Bandwidth Estimation)의 정확도가 떨어지기 때문이다. 분석된 원인을 바탕으로 2가지의 향상된 가용대역폭 측정방법을 제안하고 그 성능을 시뮬레이션을 통해 확인하였다. 제안된 방법들은 무선 네트워크가 겪을 수 있는 랜덤패킷 손실률 1% 이내에서 기존방법에 비해 대역폭 측정의 정화도가 향상되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권6호
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• pp.333-351
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• 2008

Transmission control protocols have to overcome common problems in wireless networks. TCP employing both packet loss discrimination mechanism and available bandwidth estimation algorithm, known as the good existing solution, shows significant performance enhancement in wireless networks. For instance, TCP New Jersey which exhibits high throughput in wireless networks intends to improve TCP performance by using available bandwidth estimation and congestion warning. Even though it achieves 17% and 85% improvements in terms of goodput over TCP Westwood and TCP Reno, respectively, we further improve it by exploring maximized available bandwidth estimation, handling bit-error-rate error recovery, and effective adjustment of sending rate for retransmission timeout. Hence, we propose TCP NJ+, showing that for up to 5% packet loss rate, it outperforms other TCP variants by 19% to 104% in terms of goodput when the network is in bi-directional background traffic.

• 한국항해항만학회지
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• 제31권9호
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• pp.763-769
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• 2007

A narrow loop noise bandwidth method is desirable to reduce the error of raw measurements due to the thermal noise. However, it degrades the performance of GPS initial synchronization such as mean acquisition time. And it restricts the loop noise bandwidth to a fixed value determined by the lower bound of the allowable range of carrier-to-noise power ratio, so that it is difficult to optimally track GPS signal. In order to make up for the weak points of the fixed-type narrow loop noise bandwidth method and simultaneously minimize the error of code and carrier measurements, this paper proposes a stepwise-type adaptive bandwidth algorithm for DGPS reference receivers. In this paper, it is shown that the proposed adaptive bandwidth algorithm can provide more accurate measurements than those of the fixed-type narrow loop noise bandwidth method, in view of analyzing the simulation results between two signal tracking algorithms. This paper also carries out sensitivity analysis of the proposed adaptive bandwidth algorithm due to the estimation uncertainty of carrier-to-noise power ratio. Finally the analysis results are verified by the experiment using GPS simulator.

• Journal of the Korean Statistical Society
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• 제22권2호
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• pp.361-368
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• 1993

In recent years, kernel type estimates are abundant. In this paper, we propose a bandwidth selection method for kernel regression of fixed design based on bootstrap procedure. Mathematical properties of proposed bootstrap-based bandwidth selection method are discussed. Performance of the proposed method for small sample case is compared with that of cross-validation method via a simulation study.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1299-1303
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• 2005

Over the last decade the research of end-to-end behavior on computer network has grown by orders but it has few researching in hop-by-hop behavior. We think if we know hop-by-hop behavior it can make better understanding in network behavior. This paper represent ICMP time stamp request and time stamp reply as tool of network study for learning in hop-by-hop behavior to estimate link bandwidth and link structure. We describe our idea, experiment tools, experiment environment, result and analysis, and our discussion in our observative.

• 방송공학회논문지
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• 제22권2호
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• pp.257-260
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• 2017

이 논문에서는 대역폭 추정치를 이용하여 효율적으로 디지털 변조 신호를 자동으로 분류하는 변조인식 방법을 제안한다. 변조 신호를 분류하기 위해서 일반적으로 특징변수를 이용한 방법이 널리 사용되는데, 특징변수의 정확도는 특징변수 추정에 사용되는 디지털 변조 신호의 심볼수와 심볼당 표본수에 따라 크게 영향을 받는다. 이 논문에서는 높은 과표본화율로 표본화된 신호에 대해 먼저 대략적으로 대역폭을 추정하고 이로부터 심볼당 적절한 표본수를 취할 수 있도록 표본율을 감소시킨다. 따라서 처리하는 표본수가 동일한 경우 더 많은 심볼을 사용하게 되어 변조 인식률을 높일 수 있다.

• Communications for Statistical Applications and Methods
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• 제26권6호
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• pp.611-622
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• 2019

This paper considers the estimation of the long memory parameter in nonparametric regression with strongly correlated errors. The key idea is to minimize a unified mean squared error of long memory parameter to select both kernel bandwidth and the number of frequencies used in exact local Whittle estimation. A unified mean squared error framework is more natural because it provides both goodness of fit and measure of strong dependence. The block bootstrap is applied to evaluate the mean squared error. Finite sample performance using Monte Carlo simulations shows the closest performance to the oracle. The proposed method outperforms existing methods especially when dependency and sample size increase. The proposed method is also illustreated to the volatility of exchange rate between Korean Won for US dollar.