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arxiv: 2605.06958 · v2 · pith:WZNHPLSNnew · submitted 2026-05-07 · 💻 cs.IT · eess.SP· math.IT

Hybrid Multiport Receivers for Slow Fluid Antenna Multiple Access

Jos\'e P. Gonz\'alez-Coma , Jos\'e David Vega-S\'anchez , F. Javier L\'opez-Mart\'inez This is my paper

Pith reviewed 2026-05-25 06:45 UTC · model grok-4.3

classification 💻 cs.IT eess.SPmath.IT
keywords fluid antennahybrid receivermultiport selectionRF chain reductionslow FAMAanalog combining networkmultiuser MIMO
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The pith

Fluid-antenna hybrid receiver with two RF chains matches the performance of full multiport selection in slow FAMA.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper proposes a hybrid architecture called FAHM that keeps the gains of selecting multiple ports in fluid-antenna systems but uses only a small fixed number of RF chains. It does this by inserting a low-complexity analog combining network that separates the tasks of choosing which ports to activate and of combining the signals that reach those ports. A stopping rule is introduced to decide how many ports to keep without losing too much performance, after which the hybrid combiner is designed for the remaining RF-chain budget. In multiuser slow-FAMA simulations the design with two RF chains performs nearly as well as a fully digital multiport receiver that uses many more chains, while also cutting computation by more than 60 percent when paired with an efficient port-selection routine.

Core claim

The FAHM receiver decouples port selection from signal combining through a low-complexity analog network; when only two RF chains are available the resulting architecture attains performance comparable to a fully digital conventional multiport scheme that employs a much larger number of RF chains, together with a greater than 60 percent reduction in computational cost under an efficient implementation of generalized-eigenvector port selection.

What carries the argument

Low-complexity analog combining network that decouples port selection from signal combining while preserving most of the multiport-selection benefit.

If this is right

  • Hardware cost and power consumption drop sharply because only two RF chains are needed instead of one per selected port.
  • The stopping criterion limits the number of active ports, thereby capping the performance loss from port selection.
  • The same analog network structure can be reused across different fluid-antenna port counts without redesigning the digital part.
  • Computational load falls by more than 60 percent when the port-selection step is implemented with the proposed efficient routine.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The architecture could be tested in channels with moderate mobility to see whether the slow-FAMA assumption can be relaxed without redesign.
  • Because the analog network is low-complexity, the same decoupling idea might apply to other reconfigurable-antenna systems that currently rely on full digital processing.
  • An open question left by the work is how the RF-chain budget should scale when the number of users or the port density increases.

Load-bearing premise

The analog combining network can separate port selection from signal combining without erasing most of the performance advantage that full multiport selection would otherwise provide.

What would settle it

A direct comparison, under the same slow-FAMA multiuser channel realizations, of bit-error rate or sum-rate curves for the two-RF-chain FAHM design versus a fully digital multiport receiver using the same total number of fluid-antenna ports; any sustained gap larger than the paper's reported loss would falsify the claim.

Figures

Figures reproduced from arXiv: 2605.06958 by F. Javier L\'opez-Mart\'inez, Jos\'e David Vega-S\'anchez, Jos\'e P. Gonz\'alez-Coma.

Figure 1
Figure 1. Figure 1: System model of the proposed FAHM receiver. [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Average SE for user k versus the Rice factor K for the different schemes. Results correspond to the 2D FA case with N1 × N2 = 15 × 15 and W1 × W2 = 4 × 1. Also, M = K = 5, P = 2, Np = 30, and SNR = 15 dB [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 5
Figure 5. Figure 5: Average SE for user u versus the number of selected ports P for the different schemes. Here, we assume a 2D FA case with N1 × N2 = 15 × 15 and normalized aperture W1 × W2 = 10 × 1. Also, M = U = 6, K = 10 dB, Np = 80, and SNR = 10 dB. regime to moderate values of Np. This behavior indicates that a richer multipath environment provides additional spatial diversity across the FA ports, which can be more effe… view at source ↗
Figure 3
Figure 3. Figure 3: Average SE for user u versus the number of scattered paths Np for the different schemes. Results correspond to the 2D FA case with N1 ×N2 = 15 × 15 and W1 × W2 = 5 × 4. Also, M = U = 5, P = 2, K = −20 dB, and SNR = 10 dB. with Np = 30 scattered paths, and SNR = 15 dB. As observed in the all curves, GEPort consistently achieves the highest average SE over the entire range of Rice factors under consideration… view at source ↗
Figure 6
Figure 6. Figure 6: Average SE for user u versus the transmit SNR for the different schemes and different selected-ports, namely, [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 4
Figure 4. Figure 4: Sum SE versus the number of BS antennas and users, with [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 7
Figure 7. Figure 7: Outage probability for user u vs. γ for the different schemes. Here, we assume a 2D FA case with N = 5 × 5 and normalized aperture W = 5 × 1. Also, M = U = 6, K = −10 dB, Np = 5, and SNR = 15 dB. Solid and dotted lines correspond to P = 4 and Peff = 14, respectively [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 5
Figure 5. Figure 5: Average SE for user u versus the number of selected ports P for the different schemes. Here, we assume a 2D FA case with N1 × N2 = 15 × 15 and normalized aperture W1 × W2 = 5 × 5. Also, M = U = 6, K = 10 dB, Np = 80, and SNR = 10 dB. In [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 8
Figure 8. Figure 8: Outage probability for user u versus the normalized selected-port ratio P/Peff for the different schemes. Here, we assume a 2D FA case with N = 7 × 5 and normalized aperture W = 5 × 1. Also, M = U = 8, K = −10 dB, Np = 20, SNR = 15 dB, and γ = 7 bps/Hz. adding more ports provides only marginal additional diversity or interference mitigation. We now aim to illustrate the role of the effective number of port… view at source ↗
Figure 6
Figure 6. Figure 6: Average SE for user u versus the transmit SNR for the different schemes and different selected-ports, namely, [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Outage probability for user u vs. γ for the different schemes. Here, we assume a 2D FA case with N = 5 × 5 and normalized aperture W = 2 × 1. Also, M = U = 6, K = −10 dB, Np = 5, and SNR = 15 dB. Solid and dotted lines correspond to P = 4 and P = Peff = 14, respectively [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Outage probability for user u versus the normalized selected-port ratio P/Peff for the different schemes. Here, we assume a 2D FA case with N = 7 × 5 and normalized aperture W = 2 × 1. Also, M = U = 8, K = −10 dB, Np = 20, SNR = 15 dB, and γ = 7 bps/Hz. by the elbow analysis shown in [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
read the original 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 1 minor

Summary. The paper proposes a fluid-antenna hybrid multiport (FAHM) receiver for slow fluid-antenna multiple access (FAMA) that integrates a low-complexity analog combining network to decouple port selection from signal combining. It introduces a stopping criterion to limit performance loss from port selection and designs a hybrid combiner under a fixed RF-chain budget. In multiuser evaluations under the slow FAMA model, a 2-RF-chain FAHM implementation is claimed to achieve performance comparable to a fully-digital conventional multiport scheme using many more RF chains, while also attaining over 60% computational reduction via an efficient implementation of the generalized-eigenvector port-selection method.

Significance. If the reported comparability holds under the stated channel and multiuser assumptions, the architecture would demonstrate a practical route to realizing multiport selection gains in fluid-antenna systems with drastically reduced RF hardware and complexity. This could matter for hardware-limited deployments of fluid-antenna multiple access, provided the analog network preserves the essential decoupling without introducing unmodeled impairments.

minor comments (1)
  1. The abstract states performance comparability and a 60% computational reduction but supplies no quantitative metrics, error bars, channel parameters, or evaluation setup details; adding a brief results summary (e.g., BER or sum-rate curves at specific SNR) would strengthen the claim without altering the manuscript scope.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive summary of our proposed FAHM receiver architecture, the recognition of its potential significance for hardware-limited FAMA deployments, and the recommendation of minor revision. No specific major comments were listed in the report, so we have no points to address point-by-point at this stage. We will make any minor revisions required by the editor or additional comments that may arise.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper proposes a hybrid receiver architecture for fluid-antenna systems, develops a stopping criterion and hybrid combiner design, and reports empirical performance comparability in a slow FAMA multiuser setup. No equations, derivations, or modeling steps are shown that reduce any claimed result to a fitted parameter, self-definition, or self-citation chain. The performance claims are presented as evaluation outcomes of the described construction rather than predictions forced by the inputs themselves. The architecture and methods are self-contained against external benchmarks with no load-bearing self-referential steps.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

No free parameters, axioms, or invented entities are identifiable from the abstract; the design implicitly relies on standard wireless channel models for FAMA but these are not specified.

pith-pipeline@v0.9.0 · 5730 in / 1201 out tokens · 38302 ms · 2026-05-25T06:45:56.252911+00:00 · methodology

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Works this paper leans on

31 extracted references · 31 canonical work pages · 1 internal anchor

  1. [1]

    Multiple Access Techn iques for Intelligent and Multifunctional 6G: Tutorial, Survey, and Outlook,

    B. Clerckx, Y . Mao, Z. Y ang, M. Chen, A. Alkhateeb, L. Liu, M. Qiu, J. Y uan, V . W. S. Wong, and J. Montojo, “Multiple Access Techn iques for Intelligent and Multifunctional 6G: Tutorial, Survey, and Outlook,” Proc. IEEE , vol. 112, no. 7, pp. 832–879, 2024

    work page 2024

  2. [2]

    Extremely Large-Scale MIMO: Fundamentals, Cha llenges, Solutions, and Future Directions,

    Z. Wang, J. Zhang, H. Du, W. E. I. Sha, B. Ai, D. Niyato, and M. Debbah, “Extremely Large-Scale MIMO: Fundamentals, Cha llenges, Solutions, and Future Directions,” IEEE Wireless Commun. , vol. 31, no. 3, pp. 117–124, 2024

    work page 2024

  3. [3]

    Fl uid antenna systems,

    K.-K. Wong, A. Shojaeifard, K.-F. Tong, and Y . Zhang, “Fl uid antenna systems,” IEEE Trans. Wireless Commun., vol. 20, no. 3, pp. 1950–1962, 2021

    work page 1950

  4. [4]

    Fluid Antenna System for 6G: When Bruce Lee Inspires Wireless Communications,

    K.-K. Wong, K.-F. Tong, Y . Zhang, and Z. Zhong- bin, “Fluid Antenna System for 6G: When Bruce Lee Inspires Wireless Communications,” Electron. Lett. , vol. 56, no. 24, pp. 1288–1290, 2020. [Online]. Available: https://ietresearch.onlinelibrary.wiley.com/doi/abs/10.1049/el.2020.2788

    work page doi:10.1049/el.2020.2788 2020

  5. [5]

    Fluid antennas: Reshaping intrinsic properties for fl exible radiation characteristics in intelligent wireless networks,

    W.-J. Lu, C.-X. He, Y . Zhu, K.-F. Tong, K.-K. Wong, H. Shin , and T.-J. Cui, “Fluid antennas: Reshaping intrinsic properties for fl exible radiation characteristics in intelligent wireless networks,” IEEE Commun. Mag. , vol. 63, no. 5, pp. 40–45, 2025

    work page 2025

  6. [6]

    A contempora ry survey on fluid antenna systems: Fundamentals and networkin g perspec- tives,

    H. Hong, K.-K. Wong, C.-B. Chae, H. Xu, X. Guo, F. Rostami G hadi, Y . Chen, Y . Xu, B. Liu, K.-F. Tong, and Y . Zhang, “A contempora ry survey on fluid antenna systems: Fundamentals and networkin g perspec- tives,” IEEE Trans. Netw. Sci. Eng. , vol. 13, pp. 2305–2328, 2026

    work page 2026

  7. [7]

    Fluid Antenna Multiple Acces s,

    K.-K. Wong and K.-F. Tong, “Fluid Antenna Multiple Acces s,” IEEE Trans. Wireless Commun. , vol. 21, no. 7, pp. 4801–4815, 2022

    work page 2022

  8. [8]

    Fast fluid a ntenna multiple access enabling massive connectivity,

    K.-K. Wong, K.-F. Tong, Y . Chen, and Y . Zhang, “Fast fluid a ntenna multiple access enabling massive connectivity,” IEEE Commun. Lett. , vol. 27, no. 2, pp. 711–715, 2023

    work page 2023

  9. [9]

    Slow Fluid Antenna Multiple Access,

    K.-K. Wong, D. Morales-Jimenez, K.-F. Tong, and C.-B. Ch ae, “Slow Fluid Antenna Multiple Access,” IEEE Trans. Commun. , vol. 71, no. 5, pp. 2831–2846, 2023

    work page 2023

  10. [10]

    Revisiting outage probability analysis for two-use r fluid antenna multiple access system,

    H. Xu, K.-K. Wong, W. K. New, K.-F. Tong, Y . Zhang, and C.- B. Chae, “Revisiting outage probability analysis for two-use r fluid antenna multiple access system,” IEEE Trans. Wireless Commun. , vol. 23, no. 8, pp. 9534–9548, 2024

    work page 2024

  11. [11]

    Deep learning enabled slow fluid antenna multiple access,

    N. Waqar, K.-K. Wong, K.-F. Tong, A. Sharples, and Y . Zha ng, “Deep learning enabled slow fluid antenna multiple access,” IEEE Commun. Lett., vol. 27, no. 3, pp. 861–865, 2023

    work page 2023

  12. [12]

    5G-Cod ed Fluid Antenna Multiple Access over Block Fading Channels,

    H. Hong, K.-K. Wong, K.-F. Tong, H. Xu, and H. Li, “5G-Cod ed Fluid Antenna Multiple Access over Block Fading Channels,” Electron. Lett., vol. 61, no. 1, p. e70166, 2025

    work page 2025

  13. [13]

    C oded fluid antenna multiple access over fast fading channels,

    H. Hong, K.-K. Wong, K.-F. Tong, H. Shin, and Y . Zhang, “C oded fluid antenna multiple access over fast fading channels,” IEEE Wireless Commun. Lett. , vol. 14, no. 4, pp. 1249–1253, 2025

    work page 2025

  14. [14]

    Turboch arging fluid antenna multiple access,

    N. Waqar, K.-K. Wong, C.-B. Chae, and R. Murch, “Turboch arging fluid antenna multiple access,” IEEE Trans. Wireless Commun. , 2025, early Access

    work page 2025

  15. [15]

    Compact ultra m assive antenna array: A simple open-loop massive connectivity sch eme,

    K.-K. Wong, C.-B. Chae, and K.-F. Tong, “Compact ultra m assive antenna array: A simple open-loop massive connectivity sch eme,” IEEE Trans. Wireless Commun. , vol. 23, no. 6, pp. 6279–6294, 2024

    work page 2024

  16. [16]

    Compact Ultra Massive Array (CUMA) with 4 R F Chains for Massive Connectivity,

    K.-K. Wong, “Compact Ultra Massive Array (CUMA) with 4 R F Chains for Massive Connectivity,” in Proc. IEEE W orkshop Signal Process. Adv. Wirel. Commun. (SPAWC), 2024, pp. 286–290

    work page 2024

  17. [17]

    Downlink OFDM-FAMA in 5G-NR Systems,

    H. Hong, K.-K. Wong, H. Xu, Y . Xu, H. Shin, R. Murch, D. He, and W. Zhang, “Downlink OFDM-FAMA in 5G-NR Systems,” IEEE Trans. Wireless Commun., vol. 24, no. 12, pp. 10 116–10 132, 2025

    work page 2025

  18. [18]

    Slow Flu id Antenna Multiple Access With Multiport Receivers,

    J. P . González-Coma and F. J. López-Martínez, “Slow Flu id Antenna Multiple Access With Multiport Receivers,” IEEE Wireless Commun. Lett., vol. 15, pp. 1280–1284, 2026. 12

    work page 2026

  19. [19]

    Multi-Port Selection for FAMA: Massive Connectiv ity with Fewer RF Chains than Users,

    H. Hong, K.-K. Wong, X. Zhu, H. Xu, H. Xiao, F. Rostami Gha di, and H. Shin, “Multi-Port Selection for FAMA: Massive Connectiv ity with Fewer RF Chains than Users,” arXiv preprint arXiv:2511.17897 , 2025. [Online]. Available: https://arxiv.org/abs/2511.17897

    work page arXiv 2025

  20. [20]

    Greedy and Transformer-Based Multi-Port Selection for Slow Fluid Antenna Multiple Access

    D. Perez-Adan, J. P . Gonzalez-Coma, F. J. López-Martín ez, and L. Castedo, “Greedy and transformer-based multi-port sele ction for slow fluid antenna multiple access,” arXiv preprint arXiv:2604.04589 ,

    work page internal anchor Pith review Pith/arXiv arXiv

  21. [21]

    Available: https://arxiv.org/abs/2604

    [Online]. Available: https://arxiv.org/abs/2604. 04589

    work page

  22. [22]

    V ariable-phas e-shift-based RF-baseband codesign for MIMO antenna selection,

    X. Zhang, A. F. Molisch, and S.-Y . Kung, “V ariable-phas e-shift-based RF-baseband codesign for MIMO antenna selection,” IEEE Trans. Signal Process., vol. 53, no. 11, pp. 4091–4103, November 2005

    work page 2005

  23. [23]

    Wide- band millimeter-wave propagation measurements and channel models for future wireless communication system design,

    T. S. Rappaport, G. R. MacCartney, M. K. Samimi, and S. Su n, “Wide- band millimeter-wave propagation measurements and channel models for future wireless communication system design,” IEEE Trans. Commun. , vol. 63, no. 9, pp. 3029–3056, 2015

    work page 2015

  24. [24]

    Toward a Circuit Theory of Commu- nication,

    M. T. Ivrla ˇc and J. A. Nossek, “Toward a Circuit Theory of Commu- nication,” IEEE Trans. Circuits Syst. I Regul. Pap. , vol. 57, no. 7, pp. 1663–1683, 2010

    work page 2010

  25. [25]

    Movable-antenna en hanced multiuser communication via antenna position optimizatio n,

    L. Zhu, W. Ma, B. Ning, and R. Zhang, “Movable-antenna en hanced multiuser communication via antenna position optimizatio n,” IEEE Trans. Wireless Commun. , vol. 23, no. 7, pp. 7214–7229, 2024

    work page 2024

  26. [26]

    Design and implementation of mmWave surface wave enabled fluid antennas and experimental results for fluid antenna multiple access,

    Y . Shen et al. , “Design and implementation of mmwave surface wave enabled fluid antennas and experimental results for fluid ant enna multi- ple access,” arXiv e-prints, arXiv:2405.09663 [eess] , 2024

    work page arXiv 2024

  27. [27]

    A novel pixel-based reconfigurable antenna applied in fluid antenna systems with high switching speed,

    J. Zhang et al. , “A novel pixel-based reconfigurable antenna applied in fluid antenna systems with high switching speed,” IEEE Open J. Antennas Propag., vol. 6, no. 1, pp. 212–228, 2025

    work page 2025

  28. [28]

    Scalable pixel-based reconfigurable be amform- ing networks for designing fluid antenna systems,

    J. Zhang, J. Rao, T. Kang, Z. Ming, Y . Chen, A. Umirbayev, C.-Y . Chiu, and R. Murch, “Scalable pixel-based reconfigurable be amform- ing networks for designing fluid antenna systems,” arXiv preprints, arXiv:2512.03703 [eess.SP] , 2025

    work page arXiv 2025

  29. [29]

    Metasurfac e-based fluid antennas: from electromagnetics to communications model,

    P . Ramírez-Espinosa, C. Segura-Gómez, Ángel Palomare s-Caballero, F. J. López-Martínez, and D. Morales-Jiménez, “Metasurfac e-based fluid antennas: from electromagnetics to communications model, ” arXiv e- prints, arXiv:2507.17982 [eess.SP] , 2025

    work page arXiv 2025

  30. [30]

    Pro- grammable meta-fluid antenna for spatial multiplexing in fa st fluctuating radio channels,

    B. Liu, K.-F. Tong, K.-K. Wong, C.-B. Chae, and H. Wong, “ Pro- grammable meta-fluid antenna for spatial multiplexing in fa st fluctuating radio channels,” Opt. Express , vol. 33, no. 13, pp. 28 898–28 915, Jun 2025

    work page 2025

  31. [31]

    s-FAMA-GP: A Low-Complexity S low FAMA Using Interference Interpolation,

    D. Dinis and R. Wichman, “s-FAMA-GP: A Low-Complexity S low FAMA Using Interference Interpolation,” IEEE Wireless Commun. Lett. , vol. 15, pp. 1727–1731, 2026

    work page 2026