Misalignment-Resilient Mode Group Selection for OAM-MIMO Using SIC

To meet the high-capacity and low-latency demands of 6G networks, small cell backhaul must be significantly enhanced. Orbital angular momentum (OAM) multiplexing enables multiple data streams over a single aperture pair and, when combined with MIMO and uniform circular arrays (UCAs), can improve spectral efficiency. However, OAM systems are vulnerable to inter-mode interference (IMI) caused by beam axis misalignment. This paper proposes an OAM-MIMO scheme that mitigates IMI by selecting among even-numbered, odd-numbered, and all mode groups based on channel state information (CSI). The scheme integrates stream separation using successive interference cancellation (SIC) and adaptive mode group selection according to IMI severity. Simulation results demonstrate improved capacity and robustness compared to fixed-mode approaches.