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arxiv: 2604.04371 · v1 · submitted 2026-04-06 · 💻 cs.NI · eess.SP

Comprehensive Analysis of Cellular Uplink Performance in a Dense Stadium Deployment

S.M. Haider Ali Shuvo , Hardani Ismu Nabil , Joshua Roy Palathinkal , Muhammad I. Rochman , Monisha Ghosh This is my paper

Pith reviewed 2026-05-10 20:14 UTC · model grok-4.3

classification 💻 cs.NI eess.SP
keywords uplink performance5G networksTDD bandsFDD bandsstadium deploymentcellular measurementsdense environmentsduplexing schemes
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The pith

Dense stadium measurements show high-frequency TDD bands severely limit uplink performance, forcing reliance on lower-frequency FDD bands.

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

The paper reports extensive field measurements of 5G uplink and downlink in an 80,000-seat football stadium under both empty and full conditions. It finds that high-frequency TDD bands, despite carrying most downlink traffic, cannot support wideband uplink allocations because of propagation loss and the small number of uplink slots in each TDD frame. As a result, the network falls back to lower-frequency FDD bands for uplink even when high-frequency spectrum is available. The same pattern appears near a temporary base station, indicating the duplexing structure itself contributes to the bottleneck beyond simple distance or crowding.

Core claim

High-frequency TDD bands are severely bottlenecked in the uplink by propagation loss that restricts UEs to low MCS indices and low PRB allocations, further compounded by the significantly smaller number of uplink slots compared to downlink slots in TDD frames. This produces a severe disparity in which high-frequency TDD bands carry the majority of downlink throughput while the network relies heavily on lower-frequency FDD bands for uplink. The limitation persists even near an additional base station and is therefore not solely propagation-driven but also a consequence of the downlink-heavy TDD architecture.

What carries the argument

The combination of frequency band choice and duplexing scheme (TDD with downlink-heavy slot allocation versus FDD), which controls uplink slot availability and effective transmit power use.

If this is right

  • Uplink capacity in high-frequency TDD bands remains restricted even when the network is unloaded.
  • Low-frequency FDD spectrum becomes indispensable for sustaining uplink rates in dense user scenarios.
  • The TDD frame structure itself imposes an uplink penalty independent of propagation conditions.
  • Network design for next-generation systems must account for this uplink-downlink asymmetry when selecting spectrum and duplexing methods.

Where Pith is reading between the lines

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

  • Operators may need hybrid spectrum plans that deliberately reserve lower-frequency FDD resources for uplink traffic in crowds.
  • Future TDD configurations could improve uplink performance by allocating more slots or subframes to the uplink direction.
  • The observed pattern may appear in other high-density settings such as concerts or urban events where many users share the same cell.
  • Testing uplink behavior with alternative base-station placements or different TDD ratios would help isolate how much of the limit is architectural.

Load-bearing premise

The measurements taken with the specific tool and network configuration in this stadium accurately reflect uplink behavior in other dense user environments.

What would settle it

Repeating the same uplink throughput and slot-allocation measurements in a different high-density venue that uses balanced TDD slot allocations on high-frequency bands only.

Figures

Figures reproduced from arXiv: 2604.04371 by Hardani Ismu Nabil, Joshua Roy Palathinkal, Monisha Ghosh, Muhammad I. Rochman, S.M. Haider Ali Shuvo.

Figure 1
Figure 1. Figure 1: Measurement spots at the stadium seating bowl. [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Measurement spots surrounding Verizon’s Cell on Wheels (COW) [PITH_FULL_IMAGE:figures/full_fig_p001_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Uplink transmit power and MCS distributions across different bands under unloaded (pregame) and loaded (game day) conditions. Note the heavy [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: Median difference between downlink and uplink PRB allocation [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Histogram of Verizon uplink carrier combinations during pregame [PITH_FULL_IMAGE:figures/full_fig_p004_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: CDF plots illustrating the percentage of uplink throughput delivered [PITH_FULL_IMAGE:figures/full_fig_p005_7.png] view at source ↗
Figure 9
Figure 9. Figure 9: Total aggregated uplink throughput CDF during game day for T [PITH_FULL_IMAGE:figures/full_fig_p005_9.png] view at source ↗
Figure 11
Figure 11. Figure 11: Downlink and uplink throughput distributions for T-Mobile’s [PITH_FULL_IMAGE:figures/full_fig_p006_11.png] view at source ↗
read the original abstract

Uplink performance remains a critical limitation in modern 5G networks, where UEs have to balance limited transmission power against propagation challenges. We conducted extensive measurements in the University of Notre Dame's football stadium, which has a seating capacity of 80,000 spectators, evaluating network behavior under both unloaded (pregame) and severely congested (game day) conditions, with a focus on uplink performance. Analyzing PHY-layer metrics captured via the Rohde & Schwarz QualiPoc, we show that high-frequency TDD bands in the uplink are severely bottlenecked in both the spectral and temporal domains. Despite transmitting near maximum 3GPP power limits, propagation loss inherent to high-frequency bands restricts UEs to low MCS indices and low PRB allocations, even in unloaded networks. This inability to achieve wideband allocation is further compounded by the significantly smaller number of uplink slots compared to downlink slots in TDD frames. Consequently, we observe a severe disparity between uplink and downlink: while high-frequency TDD bands carry the majority of downlink throughput, the network relies heavily on lower-frequency FDD bands for uplink. Additional measurements under favorable propagation conditions around a Verizon COW deployment located in the stadium parking lot also show that this limitation is not solely propagation-driven; rather, the duplexing scheme itself also plays a significant role. Even when TDD bands achieve higher or comparable MCS, FDD bands have a performance edge in the uplink due to the restrictive, downlink-heavy TDD architecture. These findings emphasize the indispensable role of low-frequency FDD spectrum in sustaining uplink capacity, providing insights that will help guide the design of next-generation wireless networks.

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

1 major / 3 minor

Summary. The manuscript reports extensive field measurements of cellular uplink performance in a large stadium (80,000 capacity) under pre-game unloaded and game-day congested conditions. Using Rohde & Schwarz QualiPoc for PHY-layer metrics, it concludes that high-frequency TDD bands are severely uplink-bottlenecked by propagation loss (restricting MCS and PRB allocations) and by the downlink-heavy TDD frame structure (fewer uplink slots). This produces a severe UL/DL disparity in which TDD bands dominate downlink throughput while the network relies on lower-frequency FDD bands for uplink. Additional measurements near a Verizon COW in the parking lot are presented to argue that the duplexing scheme itself contributes to the limitation beyond propagation effects alone.

Significance. If the central empirical observations hold after addressing controls, the work supplies concrete real-world evidence on uplink limitations in high-density environments and the indispensable role of low-frequency FDD spectrum for sustaining uplink capacity. The targeted contrast between loaded/unloaded conditions and the use of professional measurement tools constitute strengths that could usefully inform 5G/6G spectrum policy and network design.

major comments (1)
  1. [COW measurements section] The claim that 'the duplexing scheme itself also plays a significant role' (beyond propagation) rests on the COW parking-lot results showing TDD bands reaching comparable or higher MCS yet still underperforming FDD in uplink. Because the compared bands are high-frequency TDD versus low-frequency FDD, differences in allocated bandwidth, PRB pool size, UL duty cycle, and operator-specific scheduling remain uncontrolled. MCS comparability only equalizes per-resource efficiency; it does not normalize total delivered rate by (bandwidth × UL slot fraction). The stadium data cannot separate these factors either, since the two band classes differ in both frequency and duplex mode by design. (COW measurements section)
minor comments (3)
  1. The abstract states that full data tables and statistical details are captured, yet they are not visible in the provided text; adding summary tables with key PHY metrics, sample counts, and variability measures would improve transparency and verifiability.
  2. Explicitly list the exact carrier frequencies, channel bandwidths, and duplex configurations of the TDD and FDD bands used in all comparisons to permit assessment of generalizability.
  3. Clarify the precise definition and measurement of 'near maximum 3GPP power limits' and how UL slot fractions were quantified across TDD configurations.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the constructive and detailed feedback on our manuscript. We have carefully reviewed the major comment and will revise the paper to improve clarity and address the concerns raised regarding the interpretation of the COW measurements.

read point-by-point responses

  1. Referee: [COW measurements section] The claim that 'the duplexing scheme itself also plays a significant role' (beyond propagation) rests on the COW parking-lot results showing TDD bands reaching comparable or higher MCS yet still underperforming FDD in uplink. Because the compared bands are high-frequency TDD versus low-frequency FDD, differences in allocated bandwidth, PRB pool size, UL duty cycle, and operator-specific scheduling remain uncontrolled. MCS comparability only equalizes per-resource efficiency; it does not normalize total delivered rate by (bandwidth × UL slot fraction). The stadium data cannot separate these factors either, since the two band classes differ in both frequency and duplex mode by design. (COW measurements section)

    Authors: We appreciate the referee's careful analysis of the COW section. The measurements near the Verizon COW were performed under favorable propagation conditions to test whether the observed UL limitations in high-frequency TDD bands persist even when path loss is reduced. In these data, TDD bands achieved comparable or higher MCS values yet delivered lower uplink throughput than the low-frequency FDD bands. We agree that the bands differ in frequency, bandwidth, PRB allocation pools, UL duty cycle, and operator scheduling, and that MCS comparability alone does not fully normalize total delivered rate. We also agree that the stadium measurements, by design, confound frequency and duplex mode. In the revised manuscript we will expand the COW discussion to explicitly acknowledge these confounding factors. We will add normalized comparisons (e.g., uplink throughput per allocated PRB and per UL slot) using the measured MCS, PRB counts, and known TDD frame configurations to better quantify the contribution of the downlink-heavy TDD structure. We will further clarify that the primary claim is an empirical observation from a live commercial network rather than a fully controlled isolation of the duplexing variable. revision: yes

Circularity Check

0 steps flagged

Empirical measurement study with no derivations or self-referential claims

full rationale

The paper is a purely observational study based on PHY-layer measurements captured via the Rohde & Schwarz QualiPoc tool in a specific stadium deployment under pregame and game-day conditions. No equations, fitted parameters, predictions, first-principles derivations, or mathematical models are present that could reduce any claim to its own inputs by construction. Conclusions about uplink/downlink disparity and the role of FDD vs. TDD bands are stated as direct outcomes of the observed MCS, PRB allocations, power levels, and throughput data. No self-citations, uniqueness theorems, or ansatzes appear in the provided text. The work is self-contained as raw empirical reporting and does not invoke any load-bearing circular steps.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of field measurements and standard assumptions about 3GPP TDD/FDD configurations and measurement equipment accuracy rather than new mathematical derivations.

axioms (2)
  • standard math 3GPP standards define TDD frames with fewer uplink slots than downlink slots.
    Invoked when explaining temporal bottlenecks in uplink slot allocation.
  • domain assumption The Rohde & Schwarz QualiPoc tool provides unbiased PHY-layer metrics under real network conditions.
    Assumed for all reported MCS, PRB, and throughput observations.

pith-pipeline@v0.9.0 · 5617 in / 1400 out tokens · 35921 ms · 2026-05-10T20:14:57.374409+00:00 · methodology

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