Revisiting Spatial Block-Correlation Model for Fluid Antenna Systems: From Constant to Variable Correlations

作者：Xia-Zhi Lai, Tuo Wu, Lifeng Mai, M. Elkashlan, N. Al-Dhahir, Mérouane Debbah, G. Karagiannidis, Chau Yuen · 发表于：IEEE Journal on Selected Areas in Communications · 年份：2026 · DOI：10.1109/jsac.2025.3617021 · 被引用次数：29 · 研究领域：Computer Science

Fluid antenna systems (FAS) have emerged as a promising technology to achieve high spatial diversity by dynamically reconfiguring multiple closely spaced $N$ antenna ports. However, the inherent spatial correlation among these ports poses significant challenges for accurate performance analysis. Traditional block-correlation modeling algorithms, which partition the $N\times N$ Toeplitz-structured correlation matrix into independent $D$ blocks with constant correlation coefficients, often yield substantial approximation errors to block-correlation models, especially in scenarios with limited ports. In this paper, we revisit the spatial block-correlation model for FAS and introduce a novel block-correlation modeling algorithm in tuning the model parameters, which realizes the variable block-correlation model in practice. Our proposed approach derives closed-form expressions for the optimal block-specific correlation coefficients and develops a low-complexity heuristic algorithm that reduces the computational complexity from exponential $D^{N-D}$ to linear $(N-D)\times D$ searches, thereby achieving significantly lower approximation error compared to constant correlation models. To validate the effectiveness of our variable block-correlation modeling algorithm, we first apply it to point-to-point FAS communications with closely spaced ports, deriving analytical expressions for the joint probability density function (PDF) of channel amplitudes and ou...