Abstract: All orthogonal space-time block coding(OSTBC) schemes assume that the channel remains static during the length of the codeword.However,time selective fading channels do exist because of receiver movement,and under such conditions the conventional OSTBC detector will suffer from an error floor in the high signal-to-noise ratio case.Some detectors have been proposed under time-selective fading channels,which are mainly for the 2-Tx OSTBC case only.An improved zero forcing implementation for 4-Tx and multi-Rx systems is presented.This new scheme incurs no noise amplification,eliminates the error floor caused by channel variation and reduces computational complexity.