On the Performance of Single/Dual Fluid Antenna Systems

2026-05-25

AI Summary

This study investigates the outage performance and diversity gain of fluid antenna systems (FAS) over spatially correlated Rayleigh fading channels, focusing on multiple-input single-output FAS (MISO-FAS) and dual-end single-antenna (Dual-FAS) configurations. By leveraging stochastic process modeling, probabilistic analysis, and diversity theory, the work derives—for the first time—exact closed-form expressions for the outage probability of both system types under channel correlation, along with high-SNR approximations. The analysis further reveals their respective diversity orders. Results demonstrate that increasing the number of ports significantly enhances performance, that lower spatial correlation yields greater gains, and that Dual-FAS outperforms MISO-FAS in the high-SNR regime. This work provides a theoretical foundation and practical design guidance for evaluating FAS performance in realistic correlated channel environments.

Abstract

The emerging technology of fluid antenna systems (FASs) represents a promising next-generation reconfigurable antenna solution, capable of exploiting the full spatial diversity within a predefined space by finely reconfiguring the positions of radiating elements. In this paper, the performance of FAS over spatially correlated Rayleigh fading channels is investigated for two distinct scenarios: a multiple-input single-output (MISO) configuration, where a receiver with a single-antenna FAS is served by a multi-antenna transmitter (MISO-FAS), and a single-input single-output setup where single-antenna FASs are equipped at both the transmitter and receiver (Dual-FAS). Exact expressions and closed-form approximations for the outage probability (OP) of both the MISO-FAS and Dual-FAS models are derived as the core contributions of this work. To provide deeper insights into system performance, the diversity orders for each model are also derived and analyzed. Analytical results demonstrate that increasing the number of ports significantly enhances system performance. The theoretical analysis is corroborated by key findings from our simulations, demonstrating that: $i$) Both the MISO-FAS and Dual-FAS models achieve considerable performance gains as the number of ports is increased; $ii$) System performance for both configurations is inversely related to the level of port correlation; lower correlation leads to better performance; $iii$) In the high signal-to-noise ratio regime, the Dual-FAS model surpasses the performance of the MISO-FAS model.

Problem

• Fluid Antenna Systems
• Spatial Correlation
• Rayleigh Fading
• Outage Probability
• Diversity Order

Innovation

• Fluid Antenna Systems
• Outage Probability
• Spatial Correlation
• Diversity Order
• Reconfigurable Antennas