Weyl-Heisenberg Spaces for Robust Orthogonal Frequency Division Multiplexing

Design of Weyl-Heisenberg sets of waveforms for robust orthogonal frequency division multiplex- ing (OFDM) has been the subject of a considerable volume of work. In this paper, a complete parameterization of orthogonal Weyl-Heisenberg sets and their corresponding biorthogonal sets is given. Several examples of Weyl-Heisenberg sets designed using this parameterization are pre- sented, which in simulations show a high potential for enabling OFDM robust to frequency offset, timing mismatch, and narrow-band interference

Simulation and analysis of MIMO-OFDM for a 4G cellular network

In the disciplines that study communications, there have been increasing interest in ways and means to improve the technology behind the mobile phone. This interest extends from the antennas used to broadcast the signals to the modulation techniques used on the signals themselves. The theory is that the antennas can be improved by applying a technique known as MIMO, or multiple-input multiple-output, and the signals can be improved by the modulation technique of OFDM, or orthogonal frequency divisional multiplexing. This concept, as a whole, is known as MIMO-OFDM, and will hopefully be used as the basis of the 4G cellular network in coming years. In developing these, however, it also means covering a wide of topics such as signal interference, channel capacity, fading, et cetera. The aim of this thesis is to analyze this MIMO-OFDM concept, and all it entails, to determine if it is indeed possible to be used as the basis of a cellular network. This will be by means of a computer simulation in C/C+

Modulations multiporteuses WCP-OFDM : évaluation des performances en environnement radiomobile

Many digital communication applications are facing time and frequency selective channels that can be modelled by linear time-variant systems. Through this thesis work, we show that oversampled multicarrier modulations provide a suitable transmission technique for such an environment. However, the complexity of the transmitter-receiver remains a major obstacle for their adoption. Based on this observation, we focus on the sub-family of oversampled multicarrier modulation with short filters (WCP-OFDM), whose complexity is similar to cylic prefix OFDM. After introducing the perfect reconstruction conditions, we develop low-complexity equalizers and we study the peak-to-average power ratio issue at the output of the transmitter. Finally, we evaluate the performances of these modulations over several mobile radio propagation scenarios. Simulation results confirm the benefits of WCP-OFDM, with time-frequency localized prototypes filters, over doubly selective channels.De nombreuses applications de communications numériques font face à des canaux de transmission sélectifs en temps et en fréquence que nous pouvons assimiler à des systèmes linéaires variants dans le temps. À travers ces travaux de thèse, nous montrons que les modulations multiporteuses suréchantillonnées constituent une technique de transmission adaptée à ce type d'environnement. Cependant, la complexité algorithmique des émetteurs-récepteurs présente un frein majeur à leur adoption. Fort de ce constat, nous nous intéressons à la sous-famille des modulations multiporteuses suréchantillonnées à filtres courts (WCP-OFDM), dont la complexité algorithmique est comparable à celle de l'OFDM avec préfixe cyclique. Après avoir exprimé les conditions de reconstruction parfaite, nous développons des égaliseurs de faible complexité et étudions la problématique du rapport de puissance crête sur puissance moyenne du signal en sortie d'émetteur. Enfin, nous analysons les performances de ces modulations à travers plusieurs scénarios de propagation radiomobile. Les résultats de simulation confirment l'intérêt du WCP-OFDM, associé à des filtres prototypes bien localisés en temps et en fréquence pour faire face aux canaux doublement sélectifs