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 pre-post 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.