Showing papers by "Dong-You Choi published in 2015"
01 Jan 2015
TL;DR: This paper studies the detection and suppressing the malicious users using different outlier detection methods based on Grubb's test, Boxplot method and Dixon’s test, and shows that Box Plot method outperforms both Grubb’'s and Dixon's test for the case where multiple malicious users are present.
Abstract: A number of cooperative spectrum sensing techniques have been purposed in cognitive radio networks. However, collaboration between multiple cognitive radio (CR) users also raises a number of security issues. It has been shown that the cooperative gain can be severely affected by malfunctioning or malicious CR users in cooperative sensing. One of them is spectrum sensing data falsification (SSDF) attack, where malicious users transmit false information instead of real detection results and thereby affecting the final decision. In this paper, we study the detection and suppressing the malicious users using different outlier detection methods based on Grubb’s test, Boxplot method and Dixon’s test. We have compared their performance through simulation and receiver operating characteristics (ROC) curve shows that Boxplot method outperforms both Grubb’s and Dixon’s test for the case where multiple malicious users are present.
5 citations
TL;DR: A parameter-free spectral matting technique to automatically achieve essential matting components from the smallest eigenvectors of a Laplacian matrix that accomplish good segmentation results in photography is proposed.
Abstract: In this study, we propose a parameter-free spectral matting technique to automatically achieve essential matting components from the smallest eigenvectors of a Laplacian matrix that accomplish good segmentation results in photography. The proposed scheme is based on discarding alpha components before grouping alpha mattes for high accuracy and better performance in segmentation and compositing. The scheme’s emphasis is on finding the best alpha components of the foreground through opacity estimation in natural photographs without any required user input. The said parameter-free spectral matting technique gives us better performance in terms of seamless boundaries than the existing segmentation techniques. We have compared our scheme with the state-of-the-art interactive segmentation and matting techniques, that is, GrabCut, Graph Cut, and Bayesian Matting, etc. The results of the proposed parameter-free spectral matting scheme are promising and affirm the effectiveness of our method.
1 citations
TL;DR: In this article, the authors proposed a patch antenna with a MIMO structure, which is applicable for wireless communication equipment by combining a single patch antenna and a multi-port antenna with the relative permittivity of 4.5, loss tangent equal to 0.0035 and dielectric high of 1.03.
Abstract: This study proposed a patch antenna with a MIMO structure which is applicable for wireless communication equipment by combining a single patch antenna with a multi port. The proposed MIMO patch antenna was designed through the TRF-45 substrate with a relative permittivity of 4.5, loss tangent equal to 0.0035 and dielectric high of 1.6 mm, and the center frequency of the antenna was 2.45 GHz in the ISM (Industrial Scientific and Medical) band. The proposed MIMO patch antenna had a 500 MHz bandwidth from 2.16 ~ 2.66 GHz and 24.1% fractional bandwidth. The return loss and VSWR were -62.05 dB, 1.01 at the ISM bandwidth of 2.45 GHz. The Wibro band of 2.3 GHz was -17.43 dB, 1.33, the WiFi band of 2.4 GHz was -31.89 dB, 1.05, and the WiMax band of 2.5 GHz was -36.47 dB, 1.03. The radiation patterns included in the bandwidth were directional, and the WiBro band of 2.3 GHzhad a gain of 4.22 dBi, the WiFi band of 2.4 GHz had a gain of 4.12 dBi, the ISM band of 2.45 GHz had a gain of 4.06dBi, and the WiMax band of 2.5 GHz had a gain of 3.9 6dBi.