  Reconfigurable antennas (RAs) are a promising technology to enhance the
capacity and coverage of wireless communication systems. However, RA systems
have two major challenges: (i) High computational complexity of mode selection,
and (ii) High overhead of channel estimation for all modes. In this paper, we
develop a low-complexity iterative mode selection algorithm for data
transmission in an RA-MIMO system. Furthermore, we study channel estimation of
an RA multi-user MIMO system. However, given the coherence time, it is
challenging to estimate channels of all modes. We propose a mode selection
scheme to select a subset of modes, train channels for the selected subset, and
predict channels for the remaining modes. In addition, we propose a prediction
scheme based on pattern correlation between modes. Representative simulation
results demonstrate the system's channel estimation error and achievable
sum-rate for various selected modes and different signal-to-noise ratios
(SNRs).
