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This paper investigates the parallel interference cancellation (PIC) with hard limiter technique in direct sequence optical code division multiple access system (DS-OCDMA). The PIC technique consists of first estimating the interference by decoding all the non-desired users with a conventional correlation receiver (CCR), and then of removing the estimated interference from the received signal in order...
In this paper, we study the feasibility of using a technique called time reversal for cooperative communication on wireless sensor networks. An indoor environment containing multiple wireless sensors is used as an example in which to test and demonstrate this approach. Using numerical simulations, we study the behavior of the peak power received at a target sensor as a function of the number of cooperating...
This communication is concerned with blind separation of instantaneous mixtures of source signals based on the use of spatial quadratic time-frequency (spectrum) distributions. First, we propose a new algorithm to perform the non orthogonal joint zero-diagonalization and joint-diagonalization of given sets of matrices. We also present a selection procedure of useful time-frequency points in order...
In this paper, we address the problem of blind separation of m independent sources from their n linear mixtures in the overdetermined systems (n ges m) with unknown number of sources. After generalizing the definition of classical and nonsymmetrical contrast functions, we exhibit a wide class of generalized contrast functions using some superadditive functional and concave functions. Two practical...
This papers addresses the problem of non-negative source separation using the maximum likelihood approach. It is shown that this approach can be effective by considering that the sources are distributed according to a density having a non-negative support from which an adequate nonlinear separating function can be derived. In the particular of spectroscopic data which is our main concern, a good candidate...
A shifted non-negative matrix factorisation algorithm is derived, which offers advantages over previous matrix factorisation techniques for the purposes of single channel source separation. It represents a sound source as translations of a single frequency basis function. These translations approximately correspond to notes played by an instrument. Results are presented for a set of synthetic data,...
Currently probabilistic models of protein families, namely HMMs, are the methodology of choice for remote homology analysis. Unfortunately, the topology of such so-called Profile HMMs is rather complex which, despite sophisticated regularization techniques, is problematic for robust model estimation when only little training data is available. We propose a new HMM based protein family modeling method...
This paper considers an important class of sensor networks where the ultimate goal is not necessarily to collect each individual measurement but rather a potentially smaller set of statistics. Considering link capacity constrained topologies, we derive results that optimally allocate rate/distortion to information collected by the sensors. As a key contribution, we determine how the flow of information...
This study focuses on an information theoretic approach for estimating the number of clusters K, in microarray data sets. We present an automatic method for estimating K, based on a particular version of the normalized maximum likelihood (NML) model. The strength of the minimum description length (MDL) methods, such as the NML model, in statistical inference is to find the model structure which, in...
This paper presents an appropriate approach for the robust estimation of the noise statistics in dental panoramic X-ray images. To achieve maximum image quality after denoising, a semi-empirical scatter model is presented, leading to a local adaptive Gaussian scale mixture (GSM) model. State of the art methods use multiscale filtering of images to reduce the irrelevant part of information, based on...
In this paper, complex singular Wishart matrices and their applications are investigated. In particular, a volume element on the space of positive semidefinite m times m Hermitian matrices of rank n < m is introduced and some transformation properties are established. The Jacobian for the change of variables in the singular value decomposition of general m times n complex matrices is derived. Then...
This work presents an approach to the detection of local features in network traffic, based on the analysis of short-time maximal rate envelopes, also called statistical arrival curves. In the proposed method, the time series representing a traffic trace is divided into non-overlapping segments, which are further divided into smaller blocks. The maximal rate envelope is estimated for each block and...
At present the genomes of many organisms have been sequenced, meaning that the nucleotide structure is known but the location of genes, and most importantly, the coding regions, are unknown. Locating the coding regions is vital as they code for the proteins which control the functioning of the organism, such as its resistance to disease. We propose a new algorithm to score genomic sequences. The algorithm...
In this paper, robust decorrelating detectors for DS-CDMA communication systems with the alpha-stable channel noise are presented. The proposed detectors are derived using two optimization criteria: the least lp norm (LP) and the maximum likelihood (ML) criterion. The robust decorrelating multiuser detection schemes are implemented in an iterative form (with use of the IRLS algorithm), as well as...
The authors consider the problem of range profile compensation (RPC) in the inverse synthetic aperture radar (ISAR) imaging of fast-moving target. A novel RPC technique based on fractional Fourier transform (FrFT) is proposed. In this scheme, the compensation parameters are estimated by the FrFT based on the Shannon entropy minimizing criterion. The following burst error elimination technique and...
Most algorithms for direction-of-arrival (DOA) estimation require the noise covariance matrix to be known or to possess a known structure. In many cases the noise covariance is in fact estimated from separate measurements. This paper addresses the combined effects of finite sample sizes both in the estimated noise covariance matrix and in the data with signals present. It is assumed that a batch of...
In this paper we present a procedure for reducing the excess variance introduced by beamspace transform when it is applied to uniform circular array (UCA). Several algorithms for direction of arrival (DoA) estimation exploit modal transforms which are based on the phase-mode excitation principle (D.E.N. Davies, 1983). Here we analyze the inverse Fourier series of the array impulse response, called...
The short and highly degenerate nature of transcription factor (TF) binding sites makes their identification a challenging task. We propose a new method based on templates for identifying TF binding sites. Templates account for sequence structure and nucleotide polymorphisms present in TF binding sits providing them with a greater discriminatory capability to methods based on sequence homology
This study deals with measuring the non-Gaussianity in surface electromyogram signal (sEMG). The signal was obtained from biceps brachii muscle during elbow flexion at four different levels of maximum voluntary contraction (MVC). Typically the sEMG generated from constant-force, constant angle, non-fatiguing contractions is modelled as a stochastic process, and its probability density function (pdf)...
Time-frequency autoregressive moving-average (TFARMA) models have recently been introduced as parsimonious parametric models for underspread nonstationary random processes. In this paper, we propose linear TFARMA and TFMA parameter estimators based on a high-order TFAR model. These estimators extend the Graupe-Krause-Moore and Durbin methods for time-invariant parameter estimation to underspread nonstationary...
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