Search results for "von Mises distribution"
showing 5 items of 5 documents
A statistical model for magnitudes and angles of wavelet frame coefficients and its application to texture retrieval
2014
Abstract This paper presents a texture descriptor based on wavelet frame transforms. At each position in the image, and for each resolution level, we consider both vertical and horizontal wavelet detail coefficients as the components of a bivariate random vector. The magnitudes and angles of these vectors are computed. At each level the empirical histogram of magnitudes is modeled by a Generalized Gamma distribution, and the empirical histogram of angles is modeled by a different version of the von Mises distribution that accounts for histograms with 2 modes. Each texture is characterized by few parameters. A new distance is presented (based on the Kullback–Leibler divergence) that allows g…
The design of sum-of-cisoids channel simulators using the iterative nonlinear least square approximation method
2013
In this paper, we propose the iterative nonlinear least square approximation (INLSA) algorithm as an effective method for the design of sum-of-cisoids (SOC) channel simulators assuming non-isotropic scattering conditions. For the characterization of non-isotropic scattering scenarios, we use the von Mises distribution for describing the distribution of the angles-of-arrival (AOAs). The INLSA method relies partially on numerical optimization techniques. This method determines the SOC model parameters iteratively by minimizing the Frobenius error norm. We evaluate the performance of the INLSA method and compare the results with those obtained for the Riemann sum method (RSM) and the Lp-norm m…
A stochastic shape and orientation model for fibres with an application to carbon nanotubes
2012
Methods are introduced for analysing the shape and orientation of planar fibres from greyscale images of fibrous systems. The sequence of image processing techniques needed for segmentation of fibres is described. The identified fibres were interpreted as deformed line segments for which two shape and two orientation parameters are estimated by the maximum likelihood method. The methods introduced are shown to perform quite well for simulated systems of deformed line segments with known properties. They were applied to TEM images of carbon nanotubes embedded in polycarbonate.
Level-Crossing Rate and Average Duration of Fades in Non-Isotropic Hoyt Fading Channels with Applications to Selection Combining Diversity
2015
In this paper, we investigate the second-order statistics of Hoyt fading channels under non isotropic scattering scenarios. Assuming an asymmetrical Doppler power spectral density (PSD), we derive, in the form of single finite-range integrals, expressions for the level-crossing rate (LCR) and average duration of fades (ADF). These new results are then applied to obtain the LCR and ADF of selection combining (SC) diversity over non-isotropic Hoyt channels. In addition to their importance for studying the system performance and characterizing the dynamic behavior of multipath fading channels, the formulas derived are general in that they can be applied to many non-isotropic scattering situati…
On the autocorrelation function of Rice processes for unsymmetrical doppler power spectral densities
2010
In this paper, we derive an analytical expression for the ACF of Rice processes in the general case of unsymmetrical Doppler power spectral densities. This expression, which is obtained based on the multidimensional Gaussian distribution approach, is shown to cover the ACF of Rayleigh processes as a special case. Various numerical examples are presented to illustrate the impact of the channel parameters on the ACF. Computer simulations, considering the von Mises distribution for the angle of arrivals, are also performed to check the validity of the analytical result. Finally, the analysis of the covariance spectrum is addressed.