On the Role of Channel Gain Weighting for Fairness in Cell-Free MIMO

Abstract

This paper investigates fairness enhancement in clustered cell-free MIMO downlink systems using simple decentralized beamforming and power allocation strategies. We propose heuristics based on channel gain weighting: (i) pathgain weighted power allocation, (ii) a joint-transmission aware refinement considering aggregate channel conditions, and (iii) weighted signal to leakage and noise ratio (SLNR) beamforming. These methods prioritize users in poor channel conditions via tunable fairness parameters and require only limited information exchange between access points. Simulations show that the proposed schemes substantially improve fairness, as measured by Jain's index, with only minor impact on average throughput. Thus, they retain the scalability of decentralized approaches like SLNR beamforming while significantly enhancing fairness.