Iterative pre-distortion of the non-linear satellite channel

Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is the current European standard for satellite broadcast and broadband communications. It relies on high order modulations up to 32-amplitude/phase-shift-keying (APSK) in order to increase the system spectral efficiency. Unfortunately, as the modulation order increases, the receiver becomes more sensitive to physical layer impairments, and notably to the distortions induced by the power amplifier and the channelizing filters aboard the satellite. Pre-distortion of the non-linear satellite channel has been studied for many years. However, the performance of existing pre-distortion algorithms generally becomes poor when high-order modulations are used on a non-linear channel with a long memory. In this paper, we investigate a new iterative method that pre-distorts blocks of transmitted symbols so as to minimize the Euclidian distance between the transmitted and received symbols. We also propose approximations to relax the pre-distorter complexity while keeping its performance acceptable

Prédistorsion numérique et turbo-égalisation du canal de communication par satellite non-linéaire

In satellite communications, non-linear interference is created by the non-linear power amplifier aboard the satellite. Even in the case of a memoryless power amplifier, the channel is a non-linear system with memory due to the presence of linear filters on ground and aboard the satellite. The non-linear interference degrades the system performance, especially when considering high-order modulations or in case of several signals being amplified by the same power amplifier. In this thesis, we have proposed algorithms at the transmitter and at the receiver to digitally compensate this interference. In particular, a new predistortion algorithm has been proposed, which significantly improves state-of-the-art algorithms. Since the complexity of this algorithm is an issue, low-complexity algorithms have also been proposed and achieve almost the same performance as the initial algorithm. We have also proposed joint predistortion and turbo-equalization algorithms to further improve the system performance. / En communications par satellite, de l’interférence non-linéaire est créée par l’amplificateur de puissance non-linéaire à bord du satellite. Même si l’amplificateur peut être considéré comme sans mémoire, le canal est malgré tout un système non-linéaire avec mémoire de par la présence de filtres linéaires au sol ou à bord du satellite. L'interférence non-linéaire dégrade les performances du système, en particulier lorsqu’on considère des modulations d’ordre élevé ou plusieurs signaux amplifiés par le même amplificateur de puissance. Dans cette thèse, nous avons proposé des algorithmes à l’émetteur et au récepteur pour compenser numériquement cette interférence. En particulier, nous avons proposé un nouvel algorithme de prédistorsion qui améliore de façon significative les algorithmes de l’état-de-l’art. La complexité de l’algorithme étant très élevée, nous avons proposé des algorithmes de plus faible complexité atteignant pratiquement les mêmes performances par rapport à l’algorithme initial. Nous avons aussi proposé des algorithmes de prédistorsion et d’égalisation conjointes, permettant d'atteindre des performances plus élevées qu'avec la prédistorsion seule.Doctorat en Sciences de l'ingénieurinfo:eu-repo/semantics/nonPublishe

Low complexity block pre-distortion of a multi-carrier non-linear satellite channel

In a multi-carrier non-linear satellite communication channel, inter-symbol interference (ISI) and adjacent channel interference (ACI) occur due to the non-linear power amplifier aboard the satellite. In order to prevent a too high performance degradation, large input back-offs (IBO) are generally considered. However, if all carriers are issued from the same ground station, pre-distortion of the whole transmitted signal can be a better solution to achieve higher power efficiency aboard the satellite and/or spectral efficiency. The relation between the symbols transmitted on the channel and the received symbols is tricky for a multi-carrier system, as it involves several symbol flows. Few approaches have been proposed yet to provide an efficient algorithm with reasonable complexity in such context. In this paper, we will derive a sub-optimum algorithm for the pre-distortion of a multi-carrier non-linear satellite channel which offers a good trade-off between performance and complexity.info:eu-repo/semantics/publishe

Per block pre-distortion of a multi-carrier non-linear satellite communication channel

In this paper, we propose a pre-distortion algorithm for a two carriers non-linear satellite communication channel. In the considered scenario, two linearly modulated carriers are amplified by the same non-linear power amplifier aboard the satellite. Due to the presence of the shaping filter at the transmitter side and the receiver filter (and possibly interference with filters aboard the satellite), the received signal is affected by non-linear intersymbol interference (ISI) but also non-linear adjacent channel interference (ACI). We consider the case where the two signals are transmitted from the same gateway, so that joint pre-distortion of the two signals is possible. Simulations for the 8PSK modulation show that the algorithm is able to greatly reduce the impact of the non-linear interference.info:eu-repo/semantics/publishe

Turbo-Equalization of the Remaining Interference in a Pre-Distorted Non-Linear Satellite Channel

info:eu-repo/semantics/publishe

Orthèses plantaires : types et validités

Depuis de nombreuses années, les orthèses plantaires ont démontré leur utilité dans le traitement des différentes pathologies du pied. Depuis une dizaine d’années, le coût des orthèses plantaires a excédé les 4 billions de dollars [19]. Les récentes définitions des orthèses plantaires qu’on retrouve dans la littérature [1], [2] font référence au contrôle des mouvements anormaux du pied et à la décharge des zones d’hyperpressions plantaires, l’efficacité des orthèses plantaires semble donc connaître un franc succès clinique. Cependant, il y a peu de références en termes de validité scientifique, ce qui rend la pratique incertaine en matière de prescription d’orthèses plantaires ! Récemment, le souhait a été émis, dans quelques études, d’avoir une standardisation dans leur mode de conception et de fabrication, mais la réalité n’est toujours pas là

Proceedings of the 32nd WIC Symposium on Information Theory in the Benelux - First joint WIC/IEEE SP Symposium on Information Theory and Signal Processing in the Benelux

info:eu-repo/semantics/publishe

5G new radio over satellite links:synchronization block processing

Abstract Harmonization of terrestrial standards such that they would support satellite elements would offer several benefits. This work has started at 3GPP relating to 5G new radio (NR). Downlink initial access is one of the topics that has to be evaluated in this respect among many others. This paper studies detection of the synchronization signals included in the synchronization (SS) block of the 5G NR signal in satellite channels that have large, up to 720 kHz, Doppler frequency shift at 30 GHz carrier frequency. Furthermore, the reception of system information data in the SS block is considered. It is shown that using dedicated large frequency shift aware detectors it is possible to meet the 5G NR requirements in the detection part. However, the data part cannot be reliably received using one-shot reception at low signal-to-noise values. Some alternative solutions are considered and evaluated though some of them require changes to the standard in order to be efficient