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    Item type:Publication,
    Image watermarking based on adaptive models of human visual perception
    (2010-01-01) ;
    Hamamoto, Kazuhiko
    ;
    This paper proposes a digital image watermarking based on adaptive models of human visual perception. The algorithm exploits the local activities estimated from wavelet coefficients of each subband to adaptively control the luminance masking. The adaptive luminance is thus delicately combined with the contrast masking and edge detection and adopted as a visibility threshold. With the proposed combination of adaptive visual sensitivity parameters, the proposed perceptual model can be more appropriate to the different characteristics of various images. The weighting function is chosen such that the fidelity, imperceptibility and robustness could be preserved without making any perceptual difference to the image quality. © 2010 The Institute of Electrical Engineers of Japan.
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    Item type:Publication,
    The implementation of spectrum sensing and spectrum allocation on cognitive radio
    (2017-03-29)
    Rungsawang, Pitcha
    ;
    Cognitive Radio is a system designed to use radio spectrum in the most efficient way possible - as demands for radio spectrum have been heavily increased nowadays. The system works by allowing unlicensed users to use radio channel on the licensed users' spectrum without interfering with the licensed users. The system needs spectrum sensing to verify the usage of each specific spectrum and in ever-shifting environment, Reinforcement Learning is also used for establishing spectrum allocation as well.
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    Item type:Publication,
    Optimum watermark detection of ultrasonic echo medical images
    (2015-03-01) ;
    Attachoo, Boonwat
    ;
    Hamamoto, Kazuhiko
    To prevent unauthorized access to a person's medical images, it is widely acknowledged that the security features of confidentiality, availability and integrity should be in place. This paper proposes the watermarking of ultrasonic echo images together with optimal watermark detection, in which pseudorandom noise is added to the images for integrity. The optimum watermark detection is the integration of the generalized Gaussian distribution (ρ-GGD) and the Cauchy distribution. The results show that the proposed method gives good detection performance. The proposed method not merely achieves optimum detection using the Rao test but also leads to the highest detection probability with JPEG2000 compression. Compared with other detection methods, our proposed method exhibits better watermark detection performance even when the watermark-to-document ratio (WDR) is -50 dB.