Maximuma posteriori semi-blind channel estimation for ofdm systems operating on highly frequency and time selective channels

We propose a semi-blind block-by-block channel estimation algorithm for ofdm systems operating in highly frequency and time selective channels. This algorithm, based on the Expectation-Maximization algorithm, performs an iterative maximum a posteriori estimation of the channel. It can incorporate the coded structure of each coded block in a turbo-processing fashion to enhance channel estimation quality. Moreover, it can use the maximum a posteriori training-based channel estimation algorithm for its optimum initialization. The performance of this channel estimation algorithm is evaluated through simulation results, with and without turbo-processing and optimum initialization. It is also compared to two benchmarks based on least-square error channel estimation. Our algorithm can be potentially applied for the efficient estimation of the propagation channel in drm, dvb-t, hiper-LAN/2 and IEEE 802.11a systems.RésuméOn propose un algorithme d’estimation de canal, semi-aveugle et bloc par bloc, pour des systèmes ofdm fonctionnant sur des canaux très sélectifs en temps et en fréquence. Basé sur l’algorithme » Expectation-Maximization «, cet algorithme effectue une estimation itérative selon le maximum a posteriori. Il peut incorporer selon un traitement turbo la structure codée de chaque bloc afin d’améliorer la qualité de l’estimation de canal. De plus, il peut utiliser l’algorithme d’estimation selon le maximum a posteriori avec apprentissage pour son initialisation optimale. La performance de cet algorithme d’estimation de canal est évaluée àtravers des résultats de simulation avec ou sans traitement turbo et initialisation optimale. Elle est aussi comparée àdeux algorithmes de référence basés sur l’estimation selon les moindres carrés. Notre algorithme peut être potentiellement appliqué àl’estimation efficace du canal de propagation dans les systèmes drm, dvb-t, hiperlan/2 et ieee 802.11a.

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