On the Fundamental Scaling Laws of Fluid Antenna Systems

2025-11-05

AI Summary

Fluid antenna systems (FAS) lack rigorous asymptotic symbol error rate (SER) analysis under spatially correlated channels. Method: This paper establishes, for the first time, a fundamental scaling law linking SER to the spatial correlation structure of the channel, via asymptotic analysis yielding a tight, closed-form SER expression applicable to arbitrary modulation schemes—unifying characterization of diversity and coding gains. Results: Theoretical analysis reveals that expanding the physical antenna mobility space yields polynomial-order SER reduction, whereas merely increasing port density provides only logarithmic improvement. Consequently, we propose the core design principle: “spatial expansion outperforms port densification.” This insight provides both a theoretical foundation and quantitative guidance for FAS performance optimization and hardware deployment under realistic, non-ideal channel conditions.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Evaluation and Analysis
• Multiagent Systems: Other Foundations of Multi Agent Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines

Abstract

Fluid antenna systems (FAS) offer a promising paradigm for enhancing wireless communication by exploiting spatial diversity, yet a rigorous analytical framework for their error probability has been notably absent. To this end, this paper addresses this critical gap by unveiling the extbf{fundamental scaling laws} that govern the symbol error rate (SER) of FAS in realistic, spatially correlated channels. To establish these laws, we derive a tight, closed-form asymptotic expression for the SER applicable to a general class of modulation schemes. This result is pivotal as it establishes the fundamental scaling law governing the relationship between SER and the channel's spatial correlation structure. Based on this framework, we provide a complete characterization of the diversity and coding gains. The analysis culminates in a definitive design directive: SER can be fundamentally improved by expanding the antenna's movement space to increase diversity, while merely increasing port density within a constrained space yields diminishing returns.

Problem

• Establishing fundamental scaling laws for fluid antenna system error probability
• Deriving closed-form asymptotic expression for symbol error rate
• Characterizing diversity and coding gains in spatially correlated channels

Innovation

• Derived fundamental scaling laws for error rate
• Established closed-form asymptotic SER expression
• Characterized diversity and coding gains relationship