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arxiv: 2604.15680 · v1 · submitted 2026-04-17 · 📡 eess.SP

Measurement-Based Massive MIMO Channel Characterization and Performance Evaluation at FR3 (8 and 15 GHz) Under Equal Physical Aperture

Enrui Liu , Pan Tang , Haiyang Miao , Qi Zhen , Jianhua Zhang This is my paper

Pith reviewed 2026-05-10 08:50 UTC · model grok-4.3

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The pith

Under equal physical aperture, 15 GHz FR3 measurements show higher spectral efficiency than 8 GHz due to more antenna elements overcoming increased sparsity, despite a 3 dB coverage deficit.

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

Future 6G networks want to use new frequency bands around 8 GHz and 15 GHz for better coverage and speed. The challenge is that base station antennas have a fixed physical size, so at higher frequencies you can pack more small antennas into the same space. Researchers built a dual-band test system and took real measurements in city environments. They found the 15 GHz signals spread out less in time and space, making the channel simpler but weaker overall. By using 128 antennas instead of 32, the system gained enough extra signal strength to beat the 8 GHz version in data rate per unit bandwidth. However, at the far edges of a cell the 15 GHz link still fell short by about 3 decibels. Changing how the antennas were arranged inside the same box did not change performance much. The main lesson is that engineers must balance the natural loss of higher frequencies against the extra antennas they can fit.

Core claim

Empirical data reveals a residual coverage deficit of approximately 3.0 dB at cell edges for the 15 GHz band compared to the 8 GHz baseline, while spectral efficiency significantly outperforms the 8 GHz band due to increased element count overcoming channel sparsity.

Load-bearing premise

The measurements assume that the dual-band sounding platform accurately captures real-world propagation without significant calibration errors or site-specific biases that would alter the reported 3 dB deficit and SE gains.

Figures

Figures reproduced from arXiv: 2604.15680 by Enrui Liu, Haiyang Miao, Jianhua Zhang, Pan Tang, Qi Zhen.

Figure 1
Figure 1. Figure 1: Schematic diagram of measurement platform. [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Measurement setup in the UMa scenario, including the [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: Measured PDP across 8 GHz and 15 GHz bands. [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗
Figure 3
Figure 3. Figure 3: Illustration of the fixed-aperture array configuration for [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: DAPSs under equal physical aperture. The first column shows the measurement environments for LOS and NLOS [PITH_FULL_IMAGE:figures/full_fig_p006_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: CI path loss model fitted to measured data at 8 GHz [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: RMS delay spread results under same array aperture. [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Fig.8 [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 8
Figure 8. Figure 8: Raincloud plots of the measured RMS angular spreads for 8 GHz and 15 GHz bands under equal physical aperture [PITH_FULL_IMAGE:figures/full_fig_p009_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: Numerical relationship of theoretical received power [PITH_FULL_IMAGE:figures/full_fig_p009_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: CDF of the receive power (non-coherent combining), [PITH_FULL_IMAGE:figures/full_fig_p010_10.png] view at source ↗
Figure 12
Figure 12. Figure 12: Illustration of array topologies reconstructed from the [PITH_FULL_IMAGE:figures/full_fig_p011_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: Empirical CDF of received power for different array [PITH_FULL_IMAGE:figures/full_fig_p011_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: Numerical relationship of theoretical received power [PITH_FULL_IMAGE:figures/full_fig_p012_14.png] view at source ↗
Figure 15
Figure 15. Figure 15: Measured spectral efficiency CDFs for 8GHz ( [PITH_FULL_IMAGE:figures/full_fig_p012_15.png] view at source ↗
Figure 16
Figure 16. Figure 16: Empirical CDF of real spectral efficiency for different [PITH_FULL_IMAGE:figures/full_fig_p013_16.png] view at source ↗
read the original abstract

With the push toward 6G commercialization, Frequency Range 3 (FR3) bands, specifically 7.125-8.4 GHz and 14.8-15.3 GHz, have become focal points for achieving wide-area, high-capacity coverage. However, practical deployment is often limited by the physical aperture constraints of base station antennas. This study conducts comprehensive measurements in Urban Macro (UMa) scenarios using a unified dual-band sounding platform to evaluate channel characteristics and system performance under the strict constraint of "equal physical array aperture." The results indicate that higher frequency bands exhibit increased sparsity in both delay and spatial domains. Regarding coverage, while the 15 GHz band can theoretically accommodate four times the number of antenna elements (128 elements) within the same area to compensate for path loss, empirical data reveals a residual coverage deficit of approximately 3.0 dB at cell edges compared to the 8 GHz baseline. In contrast, the 15 GHz band excels in capacity; the increased element count effectively overcomes channel sparsity, resulting in spectral efficiency (SE) that significantly outperforms the 8 GHz band. Furthermore, the research demonstrates that for a fixed number of elements, system performance remains largely insensitive to specific array topologies (e.g., 1x32, 2x16, or 4x8). Ultimately, FR3 system performance is dictated by the trade-off between propagation characteristics and hardware-enabled gain. These findings provide a theoretical foundation for spatial-domain design and help address engineering challenges for 6G base station implementation

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

2 major / 2 minor

Summary. The manuscript presents results from a measurement campaign in urban macro (UMa) scenarios using a unified dual-band sounding platform to characterize massive MIMO channels at 8 GHz and 15 GHz under the constraint of equal physical array aperture. It reports increased delay and spatial sparsity at 15 GHz, a residual ~3 dB coverage deficit at cell edges for 15 GHz despite accommodating four times more elements (128 vs. baseline), superior spectral efficiency at 15 GHz due to the element count overcoming sparsity, and performance insensitivity to array topology (e.g., 1x32, 2x16, 4x8) for fixed element count. The work concludes that FR3 performance is governed by the propagation-hardware gain trade-off.

Significance. If the central empirical claims hold after verification, the paper supplies concrete, measurement-driven data on FR3 channel behavior and system-level trade-offs that are directly relevant to 6G base-station design. The equal-aperture constraint and dual-band unified platform approach address a practical deployment limit, while the reported topology insensitivity and SE gains offer actionable insights. The measurement-based nature (no ad-hoc parameter fitting) is a positive attribute.

major comments (2)
  1. [Abstract / Measurement platform description] Abstract and measurement/results sections: The headline claim of a residual 3.0 dB cell-edge coverage deficit at 15 GHz (after equal-aperture compensation) is obtained by comparing path-loss and beamforming gain between bands. No calibration procedure, reference-antenna data, or uncertainty budget is supplied for cross-frequency matching of antenna efficiency, cable losses, and receiver noise figures. A systematic 1–2 dB frequency-dependent bias would directly alter or remove this figure while leaving the SE comparison less affected; this detail is load-bearing for the coverage conclusion.
  2. [Results / Performance evaluation] Performance evaluation and results sections: The manuscript reports concrete values (3 dB deficit, SE improvement, topology insensitivity) but provides neither error bars, confidence intervals, nor details on the number of independent measurements, data exclusion criteria, or statistical robustness checks. This limits verification of the sparsity and SE claims.
minor comments (2)
  1. [Abstract] The abstract states '128 elements' for 15 GHz but does not explicitly state the corresponding count for the 8 GHz baseline; this should be clarified for the equal-aperture comparison.
  2. [Figures/Tables] Figure and table captions should include units, measurement bandwidth, and any normalization details to improve clarity of the reported path-loss and SE curves.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central claims rest on empirical observations rather than derivations, so the ledger contains minimal free parameters or invented entities beyond standard channel-sounding assumptions.

axioms (1)
  • domain assumption The dual-band sounding platform provides calibrated, comparable measurements across 8 GHz and 15 GHz without frequency-dependent bias exceeding the reported precision.
    Invoked implicitly when comparing coverage and SE between bands.

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