Adaptive Hybrid-Field Channel Estimation in THz XL-MIMO Systems

In this correspondence, we delve into a hybrid-field channel model for the extremely large-scale multiple-input multiple-output (XL-MIMO) system and formulate the channel estimation problem within a multi-carrier scenario. Additionally, we introduce a near-field prioritized adaptive scheme to address the issue of reliance on prior information regarding the exact numbers of near-field and far-field paths, featuring a noise-level-based stopping criterion. Focusing on narrowband and wideband scenarios, we design two algorithms within this adaptive framework based on the multiple measurement vector model. Numerical results demonstrate that the proposed adaptive hybrid-field channel estimation strategies surpass existing methods in channel estimation accuracy while maintaining low computational complexity.