Fluid Antenna-Assisted Quadrature Spatial Modulation and Its Low-Complexity Detection

Abstract

This paper presents a fluid antenna-assisted quadrature spatial modulation (FA-QSM) system that leverages flexible ports to expand the spatial signaling dimension and strengthen reliability. By independently selecting transmit ports for real and imaginary symbol components, FA-QSM achieves enhanced spectral efficiency without increasing hardware overhead. A closed-form average bit error probability (ABEP) upper bound is derived to provide the performance characterization. To overcome the computational burden of maximum likelihood detector, we propose a low-complexity two-stage orthogonal matching pursuit (TOMP) detector that achieves near-optimal performance while reducing complexity. Extensive simulations validate the theoretical analysis and demonstrate that FA-QSM with TOMP detector provides an attractive trade-off between bit error performance and complexity for next-generation wireless systems.