Joint channel estimation and equalisation of fast time-varying frequency-selective channels

Abstract

This paper addresses joint channel and data estimation for transmission over frequency-selective and time-varying channels based on a Doppler-variant channel impulse response (CIR). A discrete spreading function (DSF), which corresponds to the Doppler Fourier series of the time-varying channel taps, is introduced. The spectral leakage associated with the Fourier series representation is reduced by oversampling in Doppler-direction. This approach, however, requires joint channel estimation and equalisation (JCE). Therefore, a recursive least squares (RLS) algorithm for the DSF estimation is combined with the data detection in a reduced state diagram. Furthermore, an enhanced metric, previously introduced in De Broeck et al. (Proceedings of Second International Workshop on Multi-Carrier Spread-Spectrum, [1999]; published by Kluwer Academic Publishers: Dordrecht, 2000) for time-invariant channels, is applied here for path selection. The performance of this metric is investigated here for time-varying and frequency-selective (TV-FS) channels. The performance of the proposed approach is compared with the JCE algorithm which uses RLS estimation of a CIR by simulations.