Performance Evaluation of Energy Detector Based Spectrum Sensing for Cognitive Radio using NI USRP-2930

This paper presents the performance evaluation of the Energy Detector technique, which is one of the most popular Spectrum Sensing (SS) technique for Cognitive Radio (CR). SS is the ability to detect the presence of a Primary User (PU) (i.e. licensed user) in order to allow a Secondary User (SU) (i.e unlicensed user) to access PU's frequency band using CR, so that the available frequency bands can be used efficiently. We used for implementation an Universal Software Radio Peripheral (USRP), which is the most used Software Defined Radio (SDR) device for research in wireless communications. Experimental measurements show that the Energy Detector can obtain good performances in low Signal to Noise Ratio (SNR) values. Furthermore, computer simulations using MATLAB are closer to those of USRP measurements

Pilot Decontamination over Time Frequency and Space Domains in Multi-Cell Massive MIMO System

In this article, we show that Pilot contamination problem can be seen as a source separation problem using time, frequency, and space domains. Our method capitalizes on a nonunitary joint diagonalization of spatial quadratic time-frequency (STFD) signal representation to identify the desired and interfering users. We first compute the noise subspace from the STFD matrices selected appropriately. Secondly, we use the noise subspace obtained to estimate the Elevation (El) and the Azimuth (Az) angles for which the MUSIC cost function is maximized. Numerical simulations are provided to illustrate the effectiveness and the behavior of the proposed approach

Blind separation of complex-valued satellite-AIS data for marine surveillance: a spatial quadratic time-frequency domain approach

In this paper, the problem of the blind separation of complex-valued Satellite-AIS data for marine surveillance is addressed. Due to the specific properties of the sources under consideration: they are cyclo-stationary signals with two close cyclic frequencies, we opt for spatial quadratic time-frequency domain methods. The use of an additional diversity, the time delay, is aimed at making it possible to undo the mixing of signals at the multi-sensor receiver. The suggested method involves three main stages. First, the spatial generalized mean Ambiguity function of the observations across the array is constructed. Second, in the Ambiguity plane, Delay-Doppler regions of high magnitude are determined and Delay-Doppler points of peaky values are selected. Third, the mixing matrix is estimated from these Delay-Doppler regions using our proposed non-unitary joint zero-(block) diagonalization algorithms as to perform separation

Comparative study of soiling effect on CSP and PV technologies under semi-arid climate in Morocco

Soiling of solar collectors reduces the efficiency of both concentrating solar power (CSP) and photovoltaic technologies (PV), and increases the operations and maintenance (O&M) costs. Many countries with significant solar potential such as Morocco are located in regions characterized by dry and harsh climatic conditions, dust storms and high pollution. This study investigates the impact of soiling on PV and CSP technologies under a semi-arid climate in BenGuerir city of Morocco. For this purpose, one year of data collected from two types of soiling sensors, a Tracking Cleanliness Sensor (TraCS) and DustIQ, was evaluated. A meteorological station installed at Green Energy Park (Morocco). A period with red rain events and a dry period were selected to quantify the impact of soiling on both technologies during these periods. It is found that the soiling effect for CSP mirrors with an annually averaged soiling rate of -1.18%/day is around 5 to 6 times higher than for PV (-0.23%/day). The loss due to soiling during red rain events has been observed more pronounced compared to the dry period

Blind Separation of Cyclostationary Sources Sharing Common Cyclic Frequencies Using Joint Diagonalization Algorithm

We propose a new method for blind source separation of cyclostationary sources, whose cyclic frequencies are unknown and may share one or more common cyclic frequencies. The suggested method exploits the cyclic correlation function of observation signals to compose a set of matrices which has a particular algebraic structure. The aforesaid matrices are automatically selected by proposing two new criteria. Then, they are jointly diagonalized so as to estimate the mixing matrix and retrieve the source signals as a consequence. The nonunitary joint diagonalization (NU-JD) is ensured by Broyden-Fletcher-Goldfarb-Shanno (BFGS) method which is the most commonly used update strategy for implementing a quasi-Newton technique. The efficiency of the method is illustrated by numerical simulations in digital communications context, which show good performances comparing to other stateof-the-art methods

CORREA, JUANA TERESA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Joint Maximum Likelihood Sequence Estimation algorithm for decollision of AIS signals in maritime surveillance context

This paper addresses the Joint Maximum-Likelihood Sequence Estimation (JMLSE) algorithm of AIS (Automatic Identification System) signals decollision in maritime surveillance context. The AIS is a Self-Organized Time Division Multiple Access (SO-TDMA) system, in which vessels periodically transmit information. The main idea of this paper is the decollision of signals received by a Low Earth Orbit (LEO) satellite lead to a global surveillance of maritime traffic using JMLSE algorithm. Simulations are provided in order to evaluate the behavior of the JMLSE algorithm for separation and estimation of sources

Un nouvel algorithme de bloc diagonalisation conjointe pour la séparation de sources en mélanges convolutifs

Nous considérons le problème de la séparation aveugle de mélanges convolutifs de sources. Nous proposons un nouvel algorithme de bloc-diagonalisation conjointe d'un ensemble de matrices sous transformation non-orthogonale. Il repose sur l'optimisation algébrique d'un critère de type moindres carrés. L'intérêt majeur d'une telle approche, outre le fait qu'elle soit plus générale, est de rendre facultatif le blanchiment des observations. Des simulations informatiques sont présentées afin d'illustrer l'efficacité de l'approche proposée dans trois cas de figure : lorsque les matrices considérées sont exactement bloc-diagonales puis lorsqu'elles sont progressivement perturbées par un bruit additif Gaussien et enfin dans le contexte de la séparation aveugle de mélanges convolutifs de sources (les matrices considérées sont alors des matrices de covariance estimées)

Séparation aveugle de mélanges linéaires convolutifs de sources corrélées

In this thesis, we study the problem of the blind separation of over-determined linear convolutive real or complex mixtures of deterministic or random, statistically independent or correlated, stationary, cyclo-stationary or non-stationary and real or complex sources. We have developed approaches that combine the new (non-unitary) joint (block) diagonalization to two novel detectors of particular points to build the matrices set to be joint (block) diagonalized. The main avantages of the proposed approaches are that they are more direct since they do not require a pre-whitening stage any more and that they can be used with correlated signals. Concerning the joint lock-diagonalization algorithms, we have proposed four joint block-diagonalization algoritms. The first algorithm is iterative and based on an algebraic optimization scheme. The three other ones are based on gradient approaches. The first one relies upon a gradient approach, but the matrix gradient is approximated, whereas the two other ones are based on an exact calculus (one is based on the gradient approach, the other is based on the relative gradient approach). The optimal step size versions of these three algorithms is provided to accelerate their convergence. It means that the step size is computed algebraically at each iteration as the rooting of a 3rd-degree polynomial. The main advantage of the proposed algorithms is that they are more general (the real, positive definite or hermitian assumptions about the matrices belonging to the considered set are no more necessary and the found joint block diagonalizer can be either a unitary or a non-unitary matrix). They can also be applied to solve the joint diagonalization problem.Dans cette thèse, nous étudions le problème de la séparation aveugle de mélanges linéaires convolutifs sur-déterminés réels ou complexes de sources. Les sources considérées sont réelles ou complexes, déterministes ou aléatoires et dans ce dernier cas statistiquement indépendantes ou corrélées, stationnaires, cyclostationnaires ou non-stationnaires. Nous développons des approches combinant de nouveaux algorithmes de (bloc) diagonalisation conjointe (non unitaires) à de nouveaux détecteurs de points (temps-fréquence ou autres...) particuliers permettant d'élaborer le ou les ensembles de matrices devant être (bloc) diagonalisées conjointement. Les principaux avantages de ces approches sont d'être plus directes en ce se sens qu'elles ne requièrent plus de blanchiment préalable des observations. Elles permettent en outre d'aborder le cas réputé difficile des signaux corrélés. En ce qui concerne les algorithmes de (bloc) diagonalisation conjointe, nous proposons quatre nouveaux algorithmes sans contrainte d'unitarité sur la matrice recherchée. Le premier algorithme est de type algébrique itératif. Il est basé sur l'optimisation d'un critère de type moindres carrés. Les trois autres approches utilisent un schéma d'optimisation de type gradient. Dans un premier temps le calcul du gradient matriciel de la fonction de coût étudiée est approché. Puis dans un second temps le calcul exact est mené et deux nouveaux algorithmes sont proposés : l'un à base de gradient, l'autre à base de gradient relatif. Nous étudions les versions à pas fixe de ces trois algorithmes, puis les versions à pas optimal afin d'accélérer la convergence des algorithmes (le pas est alors recalculé algébriquement à chaque itération en cherchant les racines d'un polynôme d'ordre trois). Un lien avec la diagonalisation conjointe non unitaire est également établi. Ces algorithmes de bloc-diagonalisation conjointe possèdent l'avantage d'être généraux : les matrices de l'ensemble considéré ne sont ni nécessairement réelles, ni à symétrie hermitienne, ni définies positives et le bloc-diagonaliseur conjoint peut être une matrice unitaire ou non-unitaire

Evaluation of Aerosols Impact on global and direct irradiance attenuation under clear sky condition: A case study in Morocco

In order to reduce the consumption of fossil fuels, solar energy is a promising alternative. However, solar potential depends on several atmospheric parameters. In the absence of clouds, aerosols are the primary source of solar radiation attenuation. This study aims to examine the impact of aerosol optical depth on the attenuation of solar irradiance under clear sky conditions. For this purpose, aerosol data from satellite database and irradiance data from high-performance meteorological stations installed in two sites in Morocco were exploited. Under clear sky conditions, the results showed a decrease in global horizontal irradiance relative to the global irradiance at the top of the atmosphere of 24% for aerosol optical depth values of 0.02 and exceeding 53% for 0.6. Aerosols have a more significant impact on the direct normal irradiance under clear sky conditions; over the test data, a decrease of 66% was observed for the direct normal irradiance according to the extraterrestrial irradiance for aerosol optical depth of 0.2 and reaching 92% for 0.6