Iterative Interference Cancellation for Near-Field XL-MIMO Systems with Line-of-Sight Channels

In extra-large multiple-input multiple-output (XL-MIMO) systems, users experience near-field scenarios with spherical wavefront propagation effects that provide higher spatial resolution than traditional far-field systems, which rely on plane wave assumptions. Signal detection and interference cancellation are more challenging in near-field scenarios due to features such as spatial non-stationarity. Under line-of-sight conditions, we propose a novel weighted-rate successive interference cancellation (WR-SIC) scheme that exploits the spatial degrees of freedom inherent in near-field propagation. The proposed ordering metric leverages the enhanced spatial discrimination arising from spherical wavefront propagation to prioritize users with stronger channel characteristics. An iterative detection and decoding (IDD) scheme is then developed to exploit the degrees of freedom in XL-MIMO systems in near-field scenarios. Simulation results in hybrid near- and far-field deployments show that the proposed SIC and IDD schemes obtain improved bit error and sum rates over existing schemes.