Wideband Near-Field Channel Estimation Under Hybrid Compression: Cross-Subcarrier KL Covariance Fitting With OFDM Fresnel Model (opens in new tab)

We consider wideband channel estimation for extremely large-scale multiple-input multiple-output (XL-MIMO) arrays under hybrid analog-digital compression, in which a uniform linear array (ULA) is observed through far fewer radio-frequency (RF) chains than antennas. At a carrier frequency of 28 GHz with bandwidths reaching several hundred MHz, the standard narrowband polar-domain channel model fails: the near-field Fresnel curvature becomes sub...