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Multi-Port Selection for FAMA: Massive Connectivity with Fewer RF Chains than Users

Hanjiang Hong, Kai-Kit Wong, Xusheng Zhu, Hao Xu, Han Xiao, Farshad Rostami Ghadi, Hyundong Shin

TL;DR

This work tackles scalable multi-user connectivity in slow FAMA by introducing three port-selection strategies—EPS, IPS, and DPS—to maximize SINR under IRC at RF-chain-limited receivers. It derives a successive SINR formulation using the matrix inverse lemma, analyzes ASEP bounds, and compares algorithmic complexities, showing that IPS closely matches the optimal EPS with significantly lower complexity. Across 6 and 26 GHz bands and wideband CDL channels, IPS achieves large multiplexing gains (tens to hundreds of users) with a practical number of RF chains, while EPS offers best performance at the cost of combinatorial complexity. The results validate a practical framework for multi-port port selection in FAMA, enabling massive connectivity with fluid antennas in future wireless networks.

Abstract

Fluid antenna multiple access (FAMA) is an emerging technology in massive access designed to meet the demands of future wireless communication networks by naturally mitigating multiuser interference through the utilization of the fluid antenna system (FAS) at RF-chain-limited mobile device. The transition from single-active-port to multi-active-port on a shared RF chain for slow FAMA can greatly enhance its multiplexing capability but is not well understood. Motivated by this, this paper proposes and studies three port selection methods: the optimal exhaustive-search port selection (EPS) as a performance upper bound, and two suboptimal, low-complexity algorithms, namely incremental port selection (IPS) and decremental port selection (DPS). Then the performance of multi-active-port slow FAMA is analyzed, and the complexity of the proposed methods is compared. Simulation results indicate that the proposed methods outperform current state-of-the-art multi-port FAMA techniques. In particular, IPS achieves near-optimal performance while maintaining manageable computational complexity. This research provides a more general framework for port selection in FAMA systems.

Multi-Port Selection for FAMA: Massive Connectivity with Fewer RF Chains than Users

TL;DR

This work tackles scalable multi-user connectivity in slow FAMA by introducing three port-selection strategies—EPS, IPS, and DPS—to maximize SINR under IRC at RF-chain-limited receivers. It derives a successive SINR formulation using the matrix inverse lemma, analyzes ASEP bounds, and compares algorithmic complexities, showing that IPS closely matches the optimal EPS with significantly lower complexity. Across 6 and 26 GHz bands and wideband CDL channels, IPS achieves large multiplexing gains (tens to hundreds of users) with a practical number of RF chains, while EPS offers best performance at the cost of combinatorial complexity. The results validate a practical framework for multi-port port selection in FAMA, enabling massive connectivity with fluid antennas in future wireless networks.

Abstract

Fluid antenna multiple access (FAMA) is an emerging technology in massive access designed to meet the demands of future wireless communication networks by naturally mitigating multiuser interference through the utilization of the fluid antenna system (FAS) at RF-chain-limited mobile device. The transition from single-active-port to multi-active-port on a shared RF chain for slow FAMA can greatly enhance its multiplexing capability but is not well understood. Motivated by this, this paper proposes and studies three port selection methods: the optimal exhaustive-search port selection (EPS) as a performance upper bound, and two suboptimal, low-complexity algorithms, namely incremental port selection (IPS) and decremental port selection (DPS). Then the performance of multi-active-port slow FAMA is analyzed, and the complexity of the proposed methods is compared. Simulation results indicate that the proposed methods outperform current state-of-the-art multi-port FAMA techniques. In particular, IPS achieves near-optimal performance while maintaining manageable computational complexity. This research provides a more general framework for port selection in FAMA systems.

Paper Structure

This paper contains 18 sections, 37 equations, 7 figures, 2 tables, 3 algorithms.

Table of Contents

  1. Introduction
  2. System Model
  3. Port Selection Methods
  4. Successively SINR Expression
  5. EPS
  6. IPS
  7. DPS
  8. Performance Analysis
  9. Upper Bound on ASEP
  10. Lower Bound on ASEP
  11. Complexity Comparison
  12. Estimated Covariance Matrix
  13. Performance Evaluation
  14. Uncoded SER Performance
  15. Coded BLER Performance
  16. ...and 3 more sections

Figures (7)

  • Figure 1: Numerial complexity comparison for various port selection methods, with $U=4$, (a) $N=15$, and (b) $N = 450$.
  • Figure 2: SER performance against transmit SNR for different schemes under finite-scattering.
  • Figure 3: Upper and lower bounds on ASEP against number of UTs. Empirical SER results under finite-scattering are presented for comparison.
  • Figure 4: SER performance against the number of UTs for different schemes under interference limited finite-scattering channels.
  • Figure 5: BLER performance against SE under finite-scattering.
  • ...and 2 more figures