Capacity Maximization with Polarization-Agile Antennas in the MIMO Communication System

Polarization diversity is an important candidate for improving the channel capacity in multiple-input multiple-output (MIMO) communication systems. The use of polarization-agile antennas enables to reap important benefits of polarization diversity without the need for additional up/down-conversion chains and their associated cost and energy consumption. In this paper we propose a novel scheme of polarization pre-post coding based on the theoretical (approximate) closed-form derivation of optimal transmit/receive polarization vectors to maximize channel capacity when polarization agility is available only at one link end. We use those as basis for an iterative joint polarization prepost coding for polarization agility at both link ends. Simulations validate that the obtained capacity is in a close agreement with that obtained by exhaustive numerical search for optimal transmit/receive polarization orientation. Utilizing our scheme of joint polarization pre-post coding improves system performance by 3 dB to 5 dB in terms of the SNR.