Symbol Error Analysis for Fluid Antenna Systems with One- and Two-Dimensional Modulation Schemes

TL;DR

This paper derives exact and asymptotic symbol error probability expressions for fluid antenna systems employing various modulation schemes over Rayleigh fading channels, highlighting the impact of system parameters.

Contribution

It introduces novel closed-form SEP expressions and optimal detection structures for fluid antenna systems with multiple modulation schemes.

Findings

Exact SEP formulas are validated against simulations.

System parameters significantly influence error performance.

Asymptotic analysis provides high-SNR behavior insights.

Abstract

This paper considers a Fluid Antenna (FA) system comprising a single-antenna transmitter that communicates with a receiver equipped with an FA array with $N$ ports. The transmitter is assumed to deploy any of the modulation schemes: \textit{i}) two-sided $M$-ary amplitude-shift keying, \textit{ii}) $M$-ary phase-shift keying, iii) $M$-ary quadrature-amplitude modulation, and \textit{iv}) binary frequency-shift keying, the channels between its antenna and the receiver ports are subjected to Rayleigh fading, and the receiver chooses the best $K$ out of its $N$ ports for symbol detection. Considering that the receiver combines the signals from the best $K$ ports using maximal-ratio combining, the optimal reception structures for all the considered signaling schemes are obtained. We also present novel exact closed-form expressions for the respective symbol error probabilities (SEPs) of the FA system, as well as asymptotic approximations valid at high signal-to-noise ratios. The presented analysis is corroborated through comparisons with simulation results, showcasing the critical role of various system parameters on the SEP performance.