Outage Probability Analysis of MRC-Based Fluid Antenna Systems under Rician Fading

This paper investigates a fluid antenna system (FAS) where a single-antenna transmitter communicates with a receiver equipped with a fluid antenna (FA) over a Rician fading channel. Considering that multiple ports among the M available FA ports can be activated, the receiver selects the best K with the highest instantaneous signal-to-noise ratio (SNR) and combines the received signals at the selected ports using maximum ratio combining. The statistics of the post-combining SNR are derived using a Laplace transform-based approach, which allows to analyze the outage probability (OP) of the FAS. Additional closed-form expressions for a lower bound on the OP and the asymptotic OP at high SNR are presented. Numerical results validate the analytical framework and demonstrate the interplay of key system parameters on the performance of the considered MRC-based FAS.