Wideband Near-Field Channel Estimation Based on Parametric Symmetry for XL-MIMO Systems

In this paper, a wideband extremely large-scale multiple-input multiple-output (XL-MIMO) system is considered, and an efficient wideband near-field channel estimation algorithm is proposed. Due to the non-negligible near-field effect and beam squint effect in wideband XL-MIMO systems, the spatial domain sparsity of near-field channel matrix is broken, and thus traditional estimation algorithms become inapplicable. Meanwhile, the large number of antennas and wide bandwidth will lead to greatly high computational complexity. To decrease the computational complexity, the parametric symmetry of wideband XL-MIMO array is studied, and the extra freedom of beam squint effect in near-field region is utilized. Then, the parametric symmetry-based multiple-antenna joint (PSMJ) channel estimation algorithm is proposed to estimate the wideband near-field channel with low computational complexity. Simulation results proves that the proposed PSMJ algorithm has superior performance with lower complexity for wideband XL-MIMO systems.