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Delayed correlation has been used as a signal detection scheme for an orthogonal frequency devision multiplexing symbol with a cyclic prefix in spectrum sensing. Because of a frequency offset, the outputs of the delayed correlation do not lay only on a real axis of a complex plane. Therefore, the absolute value of the outputs of the delayed correlation is employed. Furthermore, with the use of a filter...
Although correlative codes can significantly improve the spectral performance of the rectangularly pulsed orthogonal frequency-division multiplexing (OFDM) signals, they usually have high peak to average power ratio (PAPR) values. Two methods are proposed in this paper to reduce the PAPR values of the correlatively coded OFDM signals. First, a precoding matrix for improving the spectral performance...
Underwater acoustic communication has been widely used in remotely operated vehicle (ROV) and wireless video and image transmission systems. Orthogonal frequency division multiplexing (OFDM) is effective to cope with multipath interference. However, OFDM in acoustic communication requires a very long guard interval (GI) in accordance with long delay reflected waves, which decreases an effective transmission...
A direct-conversion receiver (DCR) can reduce the power consumption and cost. However, a DCR in Orthogonal frequency division multiplexing (OFDM) systems suffer from IQ imbalance and Carrier Frequency Offset (CFO). Until this time, many algorithms are proposed to compensate IQ imbalance and CFO in OFDM. However, it is insufficient for the joint IQ imbalance and CFO estimation. On the other hand, timefrequency...
This paper presents a correlation reduction precoding scheme for joint decoding in an overloaded multiple input multiple output (MIMO)- orthogonal frequency division multiplexing (OFDM) system. In the overloaded MIMO system, the number of receive antenna elements is less than that of transmit antenna elements. Through joint maximum likelihood (ML) decoding a frequency diversity suppresses the BER...
While emphasizing the intensity or saturation component in order to obtain high-quality color images, keeping the hue component unchanged is important; thus, perceptual color models such as HSI and HSV were used. Hue-Saturation-Intensity (HSI) is a public color model, and many color applications are commonly based on this model. However, the transformation from the HSI model to RGB model after the...
A difficult challenge in obtaining clear images in underwater environment is because of poor visibility of objects due to light attenuation and color distortion. A solution to this is to do some form of enhancement of the image that eventually leads to better visualization. This paper presents a comparative analysis of three different enhancements techniques: contrast stretching (CS), histogram equalization...
This paper presents a no-reference (NR) quality assessment method for color images contaminated with additive Gaussian white noise (AGWN). The proposed metric operates on the test image and the scaled down version of the test image. Standard deviations for each of the RGB components for the test image and its scaled down version are computed. The standard deviation ratios of the scaled down version...
4K television (TV) sets are available in the retail market and some are advertised as featuring a super-resolution (SR) function. In particular, most rely on super-resolution image reconstruction (SRR) to provide high-resolution images. Recently, another SR technology that uses nonlinear signal processing (NLSP) and can work in real time has been proposed. A visual performance of the technology needs...
With easy and quick data distribution over the Internet, copyright protection and authentication become important applications of digital watermarking. The image watermarking schemes that are useful to serve these applications should perform well in some of challenging applications such as print-scan and print-cam (PSPC) applications. This challenge provides an impetus for research in the digital...
In this paper, we propose an anti-phishing technique to safeguard users against phishing attacks in the internet. The scope of our study focuses primarily on the detection of phishing websites with English content. In order to convince users on whom the website claims to be, phishers normally place brand names in different parts of the URL. We exploit this phishing pattern by assigning weights to...
In this paper, we propose a new method of embedding data and extracting it from a printed image. By embedding the data in a translation-invariant region of a target image, extraction of the target image from the background becomes unnecessary. Therefore, the data can be embedded at an arbitrary position in the target image. Additionally, a marker detection method using invisible markers is proposed...
We present an efficient hierarchical scrambling scheme for palette-based images. The goal of hierarchical scrambling of a bit stream is to make the entire stream somehow difficult to decrypt. We decompose the original palette-based image into its corresponding binary bits then introduce cyclic shifts to scramble the selected entries and change their colors. The significant parameters (i.e. target...
A variety of perceptual encryption schemes have been studied to generate visually encrypted images for protecting visual secrecy and privacy while supporting ongoing innovation and growth in the applications of digital imagery. However, typical image quality metrics such as PSNR and SSIM are not suitable to evaluate the invisibility of visually encrypted images. To overcome this issue, this paper...
Speaker recognition is a process of determining a person's identity using features in speech signals. In this study, a new speaker recognition (identification and verifica-tion) system is proposed using the responses from a computational model of the auditory system. A neurogram (2D) was constructed from the responses of the model of auditory nerve fibers for a range of characteristic frequencies...
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