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Auswahl der wissenschaftlichen Literatur zum Thema „Interférences radioélectriques“
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Dissertationen zum Thema "Interférences radioélectriques"
Ghannudi, Hamza El. „Interférences d'accès multiples et performances d'un système impulsionnel à bande ultra large transposé à 60 GHz en réseau ad hoc“. Lille 1, 2007. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2007/50376-2007-177.pdf.
Der volle Inhalt der QuelleZhang, Xiao. „Restoring dynamic spectra corrupted by radio frequency interference : Application to pulsar observation by SKA-pathfinder low-frequency NenuFAR“. Electronic Thesis or Diss., Orléans, 2024. http://www.theses.fr/2024ORLE1027.
Der volle Inhalt der QuellePulsars are rapidly rotating neutron stars that emit electromagnetic radiation signals received as periodic pulses, thereby acting as cosmic lighthouses. The excellent stability of these periodic signals makes them invaluable tools for assessing the theory of general relativity and for detecting low frequency gravitational waves. However, their observation by radio telescopes can be made difficult by radio frequency interference (RFI) of various origins. These interferences can alter the pulsar signals, which may significantly complicate the detection and precise extraction of their signatures. This thesis aims to propose deep learning techniques to mitigate the impact of RFI in pulsar observations. In particular, this thesis illustrates the interest of these methods in the case of observations carried out by NenuFAR, a pathfinder for the low-frequency segment of the upcoming Square Kilometre Array (SKA).The first part of this thesis begins presenting the astrophysical background of pulsars, emphasizing their importance and role in contemporary astronomy. It then introduces the NenuFAR radio telescope, detailing its technical specifications, observational capabilities, and unique advantages in low-frequency pulsar observations. Lastly, it reviews and summarizes RFI mitigation methods in radio astronomy, analyzing the limitations of existing technologies and identifying the key issues this thesis aims to address. In particular, current RFI mitigation methods often lead to the deletion of data identified as affected by RFI, which inevitably results in a loss of valuable information.In the second part of this thesis, we first present a simulation framework designed to generate RFI-corrupted pulsar observation data. The main goal of this framework is to build a dataset that allows the training of deep learning models, thus circumventing the recurring lack of properly labeled real data.After a thorough review of deep learning and convolutional neural networks, we highlight the shortcomings of existing RFI processing methods, which typically involve identifying and removing data suspected of being corrupted by RFI. To avoid this information loss and address this challenge, we propose a novel approach that consists in formulating the RFI attenuation problem as an image restoration task, aiming at reconstructing RFI-altered signals. Capitalizing on recent advances in deep learning, we show that this task can be efficiently achieved using a network, named RFI-DRUnet, whose architecture is inspired by a high-performance denoising network.In the following chapters, we illustrate the applicability and effectiveness of the proposed approach on simulated and real pulsar observation data, comparing it to current approaches based on deep convolutional neural networks that detect RFI. The results show that the proposed method can effectively restore RFI-corrupted observational signals under various conditions. Furthermore, we discuss the potential impact of this method for improving pulsar chronometry
Mouhouche, Belkacem. „Récepteurs de Wiener à rang réduit en CDMA : algorithmes et performances“. Paris, ENST, 2005. http://www.theses.fr/2005ENST0047.
Der volle Inhalt der QuelleIn this thesis, reduced-rank optimum and suboptimum downlink CDMA Wiener receivers are discussed and their performance is assessed. In the first part, suboptimum CDMA Wiener receivers consisting of linear chip-level equalizers followed by despreading are discussed. The equalization step can be done in a reduced-rank fashion. A reduced-rank Wiener equalizer is an equalizer in which only few coefficients are optimized. The number of optimized coefficients is called the rank of the receiver. Another low complexity method that consist of the combination of Parallel Interference Cancellation and equalization is proposed. This method is adapted to the case of multirate CDMA. In the second part, the asymptotic performance of optimum and suboptimum receivers is evaluated. To evaluate the asymptotic performance, we suppose that the spreading codes are random following a certain distribution. The SINRs can be interpreted as a random variable. When the spreading factor and the number of uses tend to infinity with fixed ratio, it can then be shown that these SINRs tend to finite deterministic limits. These limits can be used to obtain insights on the performance of a given receiver and its dependence on parameters like the channel, the noise and the load factor. Classical results that were obtained for optimum reduced rank receivers are reviewed. These results are then extended to suboptimum reduced-rank receivers. The convergence of the SINR of a reduced-rank receiver toward a full-rank receiver is shown to be very fast. In the last chapter, the performance of Space Time Transmit Diversity is discussed. STTD is assessed with both a RAKE receiver and a MMSE equalizer
Ait, Allal Dalal. „Détection d’évènements impulsionnels en environnement radioélectrique perturbé : application à l’observation des pulsars intermittents avec un système temps réel de traitement du signal“. Thesis, Orléans, 2012. http://www.theses.fr/2012ORLE2056/document.
Der volle Inhalt der QuelleThe work presented in this thesis is in the context of the intermittent impulsive event detection at Nançay Observatory. The pulsars are highly magnetized neutron stars in rapid rotation, which emit a radio beam scanning the space like a lighthouse. They are detectable with a specific instrumentation. In recent years, new classes of such pulsars were discovered. These pulsars with extreme features, especially with individual pulses more intense and irregular compared to the average, must be detected in real time in a disrupted radio environment because of telecommunication signals. This study presents some radio frequency interference (RFI) mitigation algorithms adapted to this context. Several methods are presented and compared. Among them, two were selected and compared using Monte Carlo simulations with a set of parameters to simulate the pulsar and a BPSK signal with power and different durations. In the case of researching new pulsars, an alternative method is proposed (SIPSFAR), combining research capacity in real time and robustness against RFI. It is based on 2D Fourier transform and the Radon transform. A theoretical comparative study has confronted and compared the sensitivity of this new method and the commonly method used by radio astronomers. SIPSFAR was implemented on a GPU GTX285 and tested on a large survey of the sky made at Nançay radio telescope. The results have led to a further statistical comparison from the actual data
Ait, Allal Dalal. „Détection d'évènements impulsionnels en environnement radioélectrique perturbé : application à l'observation des pulsars intermittents avec un système temps réel de traitement du signal“. Phd thesis, Université d'Orléans, 2012. http://tel.archives-ouvertes.fr/tel-00840256.
Der volle Inhalt der QuelleGu, Wei. „Robustness against interference in Internet of Things“. Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10195/document.
Der volle Inhalt der QuelleInternet of Things brought great interests in recent years for its attractive applications and intelligent structure. However, the implementation of sensor networks still presents important challenges such as the generation of Multiple-Access-Interference (MAI) with impulsive nature and the relatively high energy consumption. Both the MAI and the thermal noise should be considered due to their strong impairments each may cause on the communication quality. We employ the stable and Gaussian distributions to model the MAI and the thermal noise respectively. Firstly we study the performance of turbo codes in the direct link and we propose the p-norm as a decoding metric. This metric allows a considerable error correction performance improvement which is close to the optimal decoder. Then we investigate cooperative communications. The probability densities in the decision statistic of the optimal receiver are estimated using importance sampling approach when both the stable and Gaussian noises are present. Such a method is computationally expensive. Hence we develop an approximation approach based on the Normal Inverse Gaussian (NIG) distribution. This solution is efficient for calculation and is proximate to the optimal receiver. In addition we show that the p-norm receiver has robust performance no matter what kind of noise is dominant. At last we combine the channel coding and cooperative communication works to establish a distributed channel coding strategy. Through some simulation assessments, the energy saving strategy can be realized by choosing an appropriate distributed channel coding scheme based on the direct link quality and target bit error rate
Chen, Jiejia. „Minimisation de la consommation et gestion de l’interférence pour des transmissions multi-sauts et coopératives dans les réseaux de capteurs“. Thesis, Lille 1, 2010. http://www.theses.fr/2010LIL10097/document.
Der volle Inhalt der QuelleThe main objective of this work is firstly to study the impact of material characteristics on the consumption of a direct link or a multi-hop transmission in the wireless sensor networks applications. We specifically investigate the communications environment within the building with short transmission distances. A sensors network with low cost but many who can only capture data and transmit it is assumed. A second kind of sensors, fewer but more powerful, is capable of relaying information. Finally, the information is sent to the gateway that may be more expensive and energy-unconstrained. In this context, the physical characteristics may change between the different nodes. We want to see if these factors have an impact on strategies for multi-hop transmissions. Our major contribution is to show that the efficiency or the noise of the nodes in a heterogeneous system is an important parameter for selecting a node and the calculations of optimal relay gains. We then study methods of cooperative diversity "decode and forward" and "Amplify and forward" for improved performance in the context of impulse radio ultra-wideband. Due to the multiple access, the distribution of interference is not Gaussian. We choose the symmetric α-stable model that accurately represents the impulsive nature thanks to its heavy-tailed distribution. The stability property then allows us an analytical study of multi-hop transmissions and cooperatives. We analyze the error probability and obtain semi-analytical expressions. Finally, we propose a criterion for selecting the optimal relay based on the effect of interference