Chip-level LMMSE equalization for downlink MIMO CDMA in fast fading environments
Alexandre de Baynast, Predrag Radosavljevic, Joseph R. Cavallaro · 2005
In this paper, we consider linear MMSE equalization for wireless downlink transmission with multiple transmit and receive antennas in fast fading environments. We propose a new algorithm based on the conjugate-gradient algorithm with enhanced channel estimation. In order to be robust to the channel variations, the channel coefficients are estimated by using a weighted sliding window. Two methods to determine optimal weights with respect to the Doppler frequency are proposed. The algorithm has been simulated in a fast fading environment (vehicular A with a velocity for the mobile station of 120 km/h). We show by simulations that good performance is obtained in a correlated fast fading environment with reasonable complexity. Moreover, this approach outperforms methods based on basic sliding window or forgetting factor and the LMS algorithm.