  The performance of millimeter wave (mmWave) multiple-input multiple-output
(MIMO) systems is limited by the sparse nature of propagation channels and the
restricted number of radio frequency (RF) chains at transceivers. The
introduction of reconfigurable antennas offers an additional degree of freedom
on designing mmWave MIMO systems. This paper provides a theoretical framework
for studying the mmWave MIMO with reconfigurable antennas. Based on the virtual
channel model, we present an architecture of reconfigurable mmWave MIMO with
beamspace hybrid analog-digital beamformers and reconfigurable antennas at both
the transmitter and the receiver. We show that employing reconfigurable
antennas can provide throughput gain for the mmWave MIMO. We derive the
expression for the average throughput gain of using reconfigurable antennas in
the system, and further derive the expression for the outage throughput gain
for the scenarios where the channels are (quasi) static. Moreover, we propose a
low-complexity algorithm for reconfiguration state selection and beam
selection. Our numerical results verify the derived expressions for the
throughput gains and demonstrate the near-optimal throughput performance of the
proposed low-complexity algorithm.
