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Estimation de canal radio-mobile à évolution rapide dans les systèmes à modulation OFMD

Abstract : This thesis deals with the case of a high speed mobile receiver operating in an orthogonal-frequency-division-multiplexing (OFDM) downlink communication system. We aim to propose algorithms for channel estimation and ICI suppression in fast fading environments. We sought to directly estimate the physical channel, instead of the equivalent discrete-time channel taps. This means estimating the physical propagation parameters such as multi-path delays and multi-path complex gains. We have first developped a polynomial approximation for the time-variation of a Rayeligh complex gain with Jakes spectrum. Using this polynomial modelisation, we have investigated the Bayesian Cramer Rao Bound (BCRB) related to the estimation of time-varying and time-invariant complex gains within on OFDM symbol, assuming knowledge of delay-related information. Finally, we have proposed and analysed three iterative algorithms for estimating the time-variation complex gains (within on OFDM symbol) with ICI mitigation. The first two algorithms use a low pass interpolation or a polynomial approximation based on the estimated time-averaged gain values, and uses a SIS equalizer. They have shown a significant performance improvement for moderate Doppler spread (i.e., fd.T <= 0.1). The last algorithm uses an auto-regressive (AR) model and a Kalman filter to estimate the polynomial coefficients of the complex gains, and uses QR equalizer. It demonstrates a good performance for very high Doppler spread (i.e., fd.T> 0.1).
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Submitted on : Tuesday, April 7, 2009 - 2:14:17 PM
Last modification on : Thursday, November 19, 2020 - 12:59:40 PM
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  • HAL Id : tel-00373806, version 1



Hussein Hijazi. Estimation de canal radio-mobile à évolution rapide dans les systèmes à modulation OFMD. Traitement du signal et de l'image [eess.SP]. Institut National Polytechnique de Grenoble - INPG, 2008. Français. ⟨tel-00373806⟩



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