Hybrid Multiport Receivers for Slow Fluid Antenna Multiple Access

TL;DR

This paper introduces a hybrid multiport receiver architecture for fluid-antenna systems that maintains high performance with fewer RF chains, reducing complexity and computational load.

Contribution

It proposes a novel hybrid receiver design that decouples port selection from signal combining, enabling efficient multiuser fluid-antenna access with minimal RF chains.

Findings

A FAHM with 2 RF chains matches the performance of a fully digital scheme with many more RF chains.

The architecture reduces computational burden by over 60% when combined with an efficient port-selection method.

The stopping criterion effectively limits performance loss due to port selection.

Abstract

We propose a novel receiver architecture that preserves the performance benefits of multiport selection in fluid-antenna systems while requiring only a very small number of radio-frequency (RF) chains. The resulting fluid-antenna hybrid multiport (FAHM) receiver effectively decouples port selection from signal combining by integrating a low-complexity analog combining network similar to those used in conventional hybrid multiantenna designs. We develop a stopping criterion to determine the number of selected ports, which limits the performance loss associated with port selection, and then design the hybrid combiner for a given RF-chain budget. The FAHM architecture is evaluated in a multiuser set-up operating under slow fluid-antenna multiple access (FAMA). In this scenario, a FAHM implementation with only 2 RF chains showcases a performance comparable to a fully-digital conventional multiport scheme with a much larger number of RF chains. Additionally, the proposed receiver architecture attains over 60% reduction in computational burden when integrated with a novel efficient implementation of the state-of-the-art generalized-eigenvector port-selection method.