• Journal of Biomedical Engineering Research
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• v.15 no.3
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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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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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.

• Journal of Internet Computing and Services
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• v.9 no.6
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• pp.179-188
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• 2008

Even though a lot of researches to improve the performance of TCP over wireless networks have been performed, the performance of TCP cannot satisfy users under high packet loss rate of wireless networks. This paper addresses the problem of TCP Westwood under high packet loss rate and reveals the reasons through the extensive simulation analysis. The ABE(Available Bandwidth Estimation) of TCP westwood becomes incorrect due to TCP dynamics of loss recovery. Based on this observation, we propose two algorithms for enhancing the correctness of ABE. We have evaluated the effects of the proposed algorithms through simulation. The proposed algorithms have achieved more correct ABE under the packet loss rate less than 1%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.6
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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.

• Journal of Navigation and Port Research
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• v.31 no.9
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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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• v.22 no.2
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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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• 2005.06a
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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.

• Journal of Broadcast Engineering
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• v.22 no.2
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• pp.257-260
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• 2017

In this letter, we propose an efficient automatic modulation recognition (AMR) method which classifies digitally modulated signals by estimating the bandwidth. In AMR, feature-based methods are widely used and the accuracy of the features is highly dependent on the number of symbols and the number of samples per symbol (NSPS). In this letter, at first, we coarsely estimate the bandwidth of the oversampled signals, and then decrease the sample rate to yield adequate NSPS. As a result, more symbols are used for AMR and the correct classification rate becomes high under the same number of samples.

• Communications for Statistical Applications and Methods
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• v.26 no.6
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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.

• ETRI Journal
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• v.25 no.5
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• pp.297-304
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• 2003

A multimedia SoC often requires a large internal buffer, because it must store the whole search window to reduce the huge I/O bandwidth of motion estimation. However, the silicon area of the internal buffer increases tremendously as the search range becomes larger. This paper proposes a new method that greatly reduces the internal buffer size of a multimedia SoC while the computational cost, I/O bandwidth, and image quality do not change. In the proposed method, only the overlapped parts of search windows for consecutive macroblocks are stored in the internal buffer. The proposed method reduces the internal buffer. The proposed method reduces the internal buffer size to 1/5.0 and 1/8.8 when the search range is ${\pm}64{\times}{\pm}$64 and ${\pm}128{\times}{\pm}$128, respectively.