  In this work, we study the performance of predictor antenna (PA) systems
using hybrid automatic repeat request (HARQ). Here, the PA system is referred
to as a system with two sets of antennas on the roof of a vehicle. In this
setup, the PA positioned in the front of the vehicle can be used to predict the
channel state information at the transmitter (CSIT) for data transmission to
the receive antenna (RA) that is aligned behind the PA. Considering spatial
mismatch, due to the vehicle mobility, we derive closed-form expressions for
the optimal power allocation and the minimum average power of the PA systems
under different outage probability constraints. The results are presented for
different types of HARQ protocols and we study the effect of different
parameters on the performance of PA systems. As we show, our proposed
approximation scheme enables us to analyze PA systems with high accuracy.
Moreover, for different vehicle speeds, we show that HARQ-based feedback can
reduce the outage-limited power consumption of PA systems by orders of
magnitude.
