  In High Speed Train Communications (HSTC), the most challenging issue is
coping with the extremely fast fading channel. Compared with its static
counterpart, channel estimation on the move consumes excessive energy and
spectrum to achieve similar performance. To address this issue, we exploit the
delay correlation inherent in the linear spatial-temporal structure of
multi-antenna array, based on which the rapid fading channel may be
approximated by a virtual slow-fading channel. Subsequently, error probability
and spectral efficiency are re-examined for this staticized channel. In
particular, we formulate the quantitative tradeoff between the two metrics of
interest, by adjusting the pilot percentage in each frame. Numerical results
verify the good performance of the proposed scheme and elucidate the tradeoff.
