• Journal of Convergence for Information Technology
• /
• v.11 no.11
• /
• pp.31-37
• /
• 2021

In this paper, we propose an outlier detection algorithm called C-SCGP to prevent the degradation of localization performance based on RSS (Received Signal Strength) and AOA (Angle of Arrival) in the presence of outliers in wireless sensor networks. Since the accuracy of target estimation can significantly deteriorate due to various cause of outliers such as malfunction of sensor, jamming, and severe noise, it is important to detect and filter out all outliers. The single cluster graph partitioning (SCGP) algorithm has been widely used to remove such outliers. The proposed continuous-SCGP (C-SCGP) algorithm overcomes the weakness of the SCGP that requires the threshold and computing probability of outliers, which are impratical in many applications. The results of numerical simulations show that the performance of C-SCGP without setting threshold and probability computation is the same performance of SCGP.

• Journal of Internet Computing and Services
• /
• v.20 no.4
• /
• pp.39-46
• /
• 2019

In recently years, it has become important to detect underground objects of various marterials including metals, such as detecting the location of sink holes and pipe. For this reason, ground penetrating radar(GPR) technology is attracting attention in the field of underground detection. GPR irradiates the radar wave to find the position of the object buried underground and express the reflected wave from the object as image. However, it is not easy to interpret GPR images because the features reflected from various objects underground are similar to each other in GPR images. Therefore, in order to solve this problem, in this paper, to estimate the piping position in the GRP image according to the threshold value using the CNN (Convolutional Neural Network) model based on deep running, which is widely used in the field of image recognition, As a result of the experiment, it is proved that the pipe position is most reliably detected when the threshold value is 7 or 8.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2022.06a
• /
• pp.205-208
• /
• 2022

Multi-exposure high dynamic range (HDR) image reconstruction, the task of reconstructing an HDR image from multiple low dynamic range (LDR) images in a dynamic scene, often produces ghosting artifacts caused by camera motion and moving objects and also cannot deal with washed-out regions due to over or under-exposures. While there has been many deep-learning-based methods with motion estimation to alleviate these problems, they still have limitations for severely moving scenes. They also require large parameter counts, especially in the case of state-of-the-art methods that employ attention modules. To address these issues, we propose a frequency domain approach based on the idea that the transform domain coefficients inherently involve the global information from whole image pixels to cope with large motions. Specifically we adopt Residual Fast Fourier Transform (RFFT) blocks, which allows for global interactions of pixels. Moreover, we also employ Depthwise Overparametrized convolution (DO-conv) blocks, a convolution in which each input channel is convolved with its own 2D kernel, for faster convergence and performance gains. We call this LFFNet (Lightweight Frequency Fusion Network), and experiments on the benchmarks show reduced ghosting artifacts and improved performance up to 0.6dB tonemapped PSNR compared to recent state-of-the-art methods. Our architecture also requires fewer parameters and converges faster in training.

• Korean Journal of Cognitive Science
• /
• v.23 no.1
• /
• pp.73-95
• /
• 2012

Two experiments were conducted to verify how the factors of attentional dispersion, reason for waiting, and cue of time flow affect the perceived waiting time. In experiment 1, based on the characteristics of waiting experience that Maister(1985) suggested, levels of attentional dispersion and whether or not offering a reason for waiting were manipulated. Participants estimated elapsed time(the objective time was 10 minutes) using either prospective or retrospective estimation method. Overall results were that they overestimated the elapsed time regardless of the experimental conditions. However, both main effects of the attentional dispersion and the reason for waiting were statistically significant. That is, when attention was more dispersed and when the reason was given, overestimation of elapsed time was reduced. No difference was found between the two estimation methods, and none of the interaction was significant. Experiment 2 was a replication of Experiment 1 except that a cue of time flow was added by using scroll bar on a computer screen. Because it has been suggested that the cue can help us to manage the waiting time and result in differences between the two time estimation methods. The results showed that main effects of the attentional dispersion and the reason for waiting were significant as those in Experiment 1. In addition, main effect of time estimation method and the three-way interaction were also significant. None of two-way interaction was significant. That is, the perceived waiting time is much shorter in the retrospective method, and the effects of the attentional dispersion and the reason of waiting were dependent upon the estimation methods. Both experiments showed that offering a clear reason for waiting is more important than the attentional dispersion in reducing the perceived waiting time. Some implications of these results for the service industry and the future direction of research were discussed in the final section.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.1
• /
• pp.44-53
• /
• 1999

In this paper, we propose a pilot based time-averaging channel estimation method and analyze error performances for efficient transmission of OFDM(Orthogonal Frequency Division Multiplexing) in multipath fading environment. Frequency domain channel estimations have been used in OFDM systems to compensate signal distortions due to fading on each subcarrier. The frequency domain estimation scheme uses scattered pilot to estimate channel response by simple interpolation. This implies that the estimated channel response includes signal distortions due to the noise. In this paper, we propose time-averaged channel estimation method to remove the distortion by noise. The proposed scheme can effectively remove noise components by taking time-average of the estimated channel response after estimating frequency domain channel. The computer simulations were performed to evaluate the performance of the proposed channel estimator. For the Rician channel, we compared the performance of the proposed method to that of a conventional one using channel estimation by gaussian interpolation when SER(Symbol Error Rate) = $10^{-4}$, and compared to perfect channel estimation case. The proposed method showed differences of 0.07 dB, 0.6 dB compared to perfect channel estimation and improvements of 1.7 dB, 1.9 dB for 16 QAM, 64 QAM respectively compared to conventional method.

• Korean Journal of Remote Sensing
• /
• v.39 no.6_1
• /
• pp.1185-1193
• /
• 2023

The increasing interest in soil moisture data from satellite imagery for applications in hydrology, meteorology, and agriculture has led to the development of methods to produce variable-resolution soil moisture maps. Research on accurate soil moisture estimation using satellite imagery is essential for remote sensing applications. The purpose of this study is to generate a soil moisture estimation map for a test area using KOMPSAT-3/3A and KOMPSAT-5 SAR imagery and to quantitatively compare the results with soil moisture data from the Soil Moisture Active Passive (SMAP) mission provided by NASA, with a focus on accuracy validation. In addition, the Korean Environmental Geographic Information Service (EGIS) land cover map was used to determine soil moisture, especially in agricultural and forested regions. The selected test area for this study is the western part of Jeju, South Korea, where input data were available for the soil moisture estimation algorithm based on the Water Cloud Model (WCM). Synthetic Aperture Radar (SAR) imagery from KOMPSAT-5 HV and Sentinel-1 VV were used for soil moisture estimation, while vegetation indices were calculated from the surface reflectance of KOMPSAT-3 imagery. Comparison of the derived soil moisture results with SMAP (L-3) and SMAP (L-4) data by differencing showed a mean difference of 4.13±3.60 p% and 14.24±2.10 p%, respectively, indicating a level of agreement. This research suggests the potential for producing highly accurate and precise soil moisture maps using future South Korean satellite imagery and publicly available data sources, as demonstrated in this study.

• Journal of KIISE:Computer Systems and Theory
• /
• v.35 no.9_10
• /
• pp.466-475
• /
• 2008

Owing to the improved wireless communication technologies, it is possible to provide streaming service of multimedia with PDAs and mobile phones in addition to desktop PCs. Since mobile client devices have low computing power and low network bandwidth due to wireless network, the transcoding technology to adapt media for mobile client devices considering their characteristics is necessary. Transcoding servers transcode the source media to the target media within corresponding grades and provide QoS in real-time. In particular, an effective load balancing policy for transcoding servers is inevitable to support QoS for large scale mobile users. In this paper, the transcoding load estimation algorithm is proposed for load balance on the distributed transcoding environments. The proposed algorithm estimates transcoding time from transcoding server information, movie information and target transcoding bit-rate. The estimated transcoding time is proved based on experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.8 s.350
• /
• pp.35-43
• /
• 2006

In the paper, we propose a new method for power optimization that uses path balancing based on stochastic estimation of glitch in Statistical Static Timing Analysis (SSTA). The proposed method estimates the probability of glitch occurrence using tightness probability of each node in timing graph. In addition, we propose efficient gate sizing technique for glitch reduction using accurate calculation of sizing effect in delay considering probability of glitch occurrence. The efficiency of proposed method has been verified on ISCAS85 benchmark circuits with $0.16{\mu}m$ model parameters. Experimental results show up to 8.6% of accuracy improvement in glitch estimation and 9.5% of optimization improvement.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.6
• /
• pp.10-10
• /
• 2002

This paper introduces the high-resolution channel estimation technique which are used to estimate the first arrival multipath delay component. The proposed technique yields the precise estimate of the first time arrival which is directly related to the performance of TDOA-based position location. The proposed technique utilizes the transformed auto-correlation function of received common pilot signal in frequency domain, its samples compose the hermitian Toeplitz matrix at sequel. Then the time delay components could be estimated with precision by the analysis of eigen-structure of corresponding matrix. In this paper, obeying the modified CODIT model, the performance of the PR-IPDL(Pseudo Random-Idle Period Downlink) and TA-IPDL(Time Aligned-Idle Period Downlink considered as 3GPP position location technique will be exploited systematically through the computer simulations with applying the proposed technique.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.6
• /
• pp.268-276
• /
• 2002

This paper introduces the high-resolution channel estimation technique which are used to estimate the first arrival multipath delay component. The proposed technique yields the precise estimate of the first time arrival which is directly related to the performance of TDOA-based position location. The proposed technique utilizes the transformed auto-correlation function of received common pilot signal in frequency domain, its samples compose the hermitian Toeplitz matrix at sequel. Then the time delay components could be estimated with precision by the analysis of eigen-structure of corresponding matrix. In this paper, obeying the modified CODIT model, the performance of the PR-IPDL(Pseudo Random-Idle Period Downlink) and TA-IPDL(Time Aligned-Idle Period Downlink considered as 3GPP position location technique will be exploited systematically through the computer simulations with applying the proposed technique.