High SNR Probabilities of Continuous Fluid Antenna Systems in Ricean Environments

TL;DR

This paper derives the first analytical approximations for the high SNR probability of continuous fluid antenna systems in Ricean channels, highlighting the impact of channel variations and the Ricean K-factor on performance.

Contribution

It provides the first closed-form expression for the Euler characteristic density of a non-central chi-squared field and analyzes the high SNR behavior of CFAS in Ricean environments.

Findings

Accurate high SNR probability approximations for CFAS in Ricean channels.

First closed-form Euler characteristic density for non-central chi-squared fields.

Channel variations and K-factor significantly influence CFAS performance.

Abstract

We consider a single-user (SU) continuous fluid antenna system (CFAS) employing matched filtering (MF) operating over a Ricean fading channel. Focusing on the upper tail of the received signal-to-noise ratio (SNR) distribution (the high SNR probability (HSP)), we derive accurate approximations for the HSP in 1, 2, and 3 dimensions using the expected Euler characteristic (EEC), presenting the first analytical results for a CFAS in a Ricean environment. In the process, we provide the first closed-form expression for the Euler characteristic density of a non-central chi-squared random field. We then examine the impact of the Ricean K-factor on the CFAS performance, emphasizing the critical role of channel variations in achieving a strong HSP.