Hierarchical Group Method for Over-the-Air Channel Calibration in Cell-Free Massive MIMO
Cell-Free massive multiple-input multiple-output (CF-mMIMO) is a key technology for 6G networks, enabling efficient downlink beamforming by exploiting the channel reciprocity under time-division duplex (TDD) operation. However, mismatched radio-frequency (RF) gains in transceiver chains render the composite channel non...