Comprehensive Analysis of Cellular Uplink Performance in a Dense Stadium Deployment

2026-04-05

AI Summary

This study addresses the uplink performance limitations of high-frequency TDD in ultra-dense 5G deployments, where asymmetric slot configurations and propagation losses hinder user experience. Leveraging real-world measurements from a stadium accommodating 80,000 spectators, the authors compare uplink performance between idle (pre-event) and highly congested (during-event) conditions for both TDD (high-band) and FDD (low-band) systems. Physical-layer metrics were collected using Rohde & Schwarz QualiPoc tools, complemented by multi-scenario measurements around Verizon’s Cells-on-Wheels (COW) deployment sites. The findings reveal that even under favorable propagation conditions, TDD uplink capacity remains constrained by its frame structure, compelling operational networks to rely predominantly on low-band FDD for uplink traffic. This work quantifies, for the first time in a real-world ultra-dense environment, the significant imbalance between uplink and downlink capabilities, underscoring the critical role of low-frequency FDD in sustaining uplink capacity.

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.

Problem

• uplink performance
• 5G networks
• TDD
• FDD
• dense deployment

Innovation

• uplink bottleneck
• TDD-FDD asymmetry
• dense stadium deployment
• PHY-layer measurement
• spectral-temporal limitation