Structured PARAFAC Channel Estimation for Flexible Intelligent Metasurface Receivers

Overview & Synopsis

Flexible intelligent metasurfaces (FIMs) create geometric diversity through aperture morphing, but their configuration-dependent responses complicate uplink channel estimation. This letter considers multiple users sharing a common angular response and develops a structured PARAFAC model across calibrated FIM configurations. Its known identity factor and rank-one pilot-weighted channel factor enable deterministic, noniterative algebraic factor recovery through per-element rank-one approximations, reference-state normalization, global rank-one projection, and a least-squares morphing-factor update. The recovered spatial and morphing factors are then jointly matched to the calibrated manifold to estimate the common angles, user gains, and configuration-dependent channels. Simulations demonstrate accurate recovery and show that out-of-plane morphing resolves the azimuth-sign ambiguity of an undeformed planar aperture; an angular-spread experiment quantifies the mismatch when the common-response assumption is relaxed.