Low-Complexity Multi-User MIMO Uplink Transmission Assisted by Dual-Polarized Reconfigurable Intelligent Surface

With further research on dual-polarized antennas and reconfigurable intelligent surface (RIS), dual-polarized RIS has become the focus of research attention in recent years. It retains the advantage of being programmable, cost- and energy-effective and expands the freedom of polarization domain. Meanwhile, the ever-increasing growth in the size of wireless connections poses a significant challenge to system performance, such as system spectral efficiency (SE). To this end, we investigate the application of dual-polarized RIS in far-field multi-user multi-input multi-output (MIMO) uplink transmission. We first establish a dual-polarized model of the system and formulate the corresponding optimization problem for SE maximization. Due to the presence of dual polarization, the channel dimension is doubled and the system is influenced by the cross-polarization interference. To handle the above issues, a low-complexity joint optimization algorithm is proposed in this paper, which takes the cross-polarization interference into account. The effectiveness of the proposed algorithm for enhancing the system SE is demonstrated by numerical results.