Application des ondelettes dans les récepteurs de systèmes radiomobiles à grande efficacité spectrale
Romaric Mvone Evina, Jean-Michel Rouvaen · OpenGrey (Institut de l'Information Scientifique et Technique) · 2008
High speed access resorts to high spectral efficiency modulations, like QAM ones. This leads to a joint increase in inter-symbol interferences, transmission errors. Signal dynamics (amplifier non-linearities), complexity of receiver synchronization techniques and, finally, complexity and cost of receivers. The wavelets may be substituted to Fourier analysis in the study of almost all physical signals. The discrete wavelet transform algorithms are even faster than the fast Fourier transform (FFT). Despite, the wavelet theory grows on very slowly in the digital communication field. The purpose of this thesis is to introduce wavelet processing in various QAM receivers functions, like the demodulation of received signal, the estimation of their power and synchronisation. In chapter one, “Wavelet transform”, the signal analysis using wavelets is briefly presented. In chapter two, “QAM modulations : recuperation of the carrier”, the problem of carrier synchronization is exposed. In chapter three, “Wavelet demodulation”, a method for QAM signal demodulation is proposed, the equivalence with base-band modelling is established and a blind power detector is developed. In chapter four, “Carrier recuperation using wavelets”, a method for discrimination between various QAM modulations is described, which enables the activation of the carrier detector suggested afterwards. We terminate with concluding remarks and some propositions for our future research