  Adaptation of a wireless system to the polarization state of the propagation
channel can improve reliability and throughput. This paper in particular
considers polarization reconfigurable multiple input multiple output (PR-MIMO)
systems, where both transmitter and receiver can change the (linear)
polarization orientation at each element of their antenna arrays. We first
introduce joint polarization pre-post coding to maximize bounds on the capacity
and the maximum eigenvalue of the channel matrix. For this we first derive
approximate closed form equations of optimal polarization vectors at one link
end, and then use iterative joint polarization pre-post coding to pursue joint
optimal polarization vectors at both link ends. Next we investigate the
combination of PR-MIMO with hybrid antenna selection / maximum ratio
transmission (PR-HS/MRT), which can achieve a remarkable improvement of channel
capacity and symbol error rate (SER). Further, two novel schemes of element
wise and global polarization reconfiguration are presented for PR-HS/MRT.
Comprehensive simulation results indicate that the proposed schemes provide 3
to 5 dB SNR gain in PR-MIMO spatial multiplexing and approximately 3 dB SNR
gain in PRHS/ MRT, with concomitant improvements of channel capacity and SER.
