说明：  ns STBC for purely time-selective channels by transforming the time-selective channels into frequency-selective channels, and by adjusting existing space–time code designs over frequency-selective MIMO channels to collect joint space–Doppler gains over purely time-selective MIMO channels. Further, [14] uses the ideas of [12] to develop a space–time code that can achieve full space-delay-Doppler diversity for any number of transmit–receive antennas. However, to quantify the maximum Doppler diversity order [2], the above papers rely on a parsimonious critically sampled complex-exponential basis expansion model (CCE-BEM) for the underlying purely time-selective or doubly-selective channels [16]. However, the CCE-BEM may have a large modeling error under certain channel conditions