A Tutorial on 3GPP Rel-19 Channel Modeling for 6G FR3 (7-24 GHz): From Standard Specification to Simulation Implementation

The upper-mid band (7-24 GHz), designated as Frequency Range 3 (FR3), has emerged as a definitive ``golden band" for 6G networks, strategically balancing the wide coverage of sub-6 GHz with the high capacity of mmWave. To compensate for the severe path loss inherent to this band, the deployment of Extremely Large Aperture Arrays (ELAA) is indispensable. However, the legacy 3GPP TR 38.901 channel model faces critical validity challenges when applied to 6G FR3, stemming from both the distinct propagation characteristics of this frequency band and the fundamental physical paradigm shift induced by ELAA. In response, 3GPP Release 19 (Rel-19) has validated the model through extensive new measurements and introduced significant enhancements. This tutorial provides a comprehensive guide to the Rel-19 channel model for 6G FR3, bridging the gap between standardization specifications and practical simulation implementation. First, we provide a high-level overview of the fundamental principles of the 3GPP channel modeling framework. Second, we detail the specific enhancements and modifications introduced in Rel-19, including the rationale behind the new Suburban Macro (SMa) scenario, the mathematical modeling of ELAA-driven features such as near-field and spatial non-stationarity, and the recalibration of large-scale parameters. Overall, this tutorial serves as an essential guide for researchers and engineers to master the latest 3GPP channel modeling methodology, laying a solid foundation for the accurate design and performance evaluation of future 6G FR3 networks.

💡 Research Summary

This tutorial provides a comprehensive guide to the 3GPP Release 19 (Rel‑19) channel model for the 7–24 GHz frequency range, designated as Frequency Range 3 (FR3), which is poised to become the “golden band” for 6G networks. The authors begin by outlining the strategic importance of FR3, which balances the wide coverage of sub‑6 GHz with the high capacity of millimeter‑wave bands, and they emphasize the necessity of Extremely Large Aperture Arrays (ELAA) to overcome the severe path‑loss at these frequencies.

The legacy 3GPP TR 38.901 model, originally developed for 5G, is shown to be inadequate for FR3 because it relies heavily on linear interpolation between sub‑6 GHz and mmWave measurements and assumes far‑field, wide‑sense stationary propagation—assumptions that break down when ELAA apertures extend the radiative near‑field to hundreds of meters. To address these gaps, Rel‑19 introduces a series of enhancements that are systematically described in the paper.

First, a new Suburban Macro (SMa) scenario is defined, with recalibrated large‑scale parameters (LSPs) such as path‑loss exponents, LOS probability functions, and outdoor‑to‑indoor (O2I) penetration loss models that capture the non‑linear frequency dependence observed in measurement campaigns. Second, the model incorporates a near‑field channel formulation that replaces the planar‑wave assumption with a spherical‑wavefront correction. This correction adjusts phase and delay for each antenna element based on its exact position relative to the transmitter, thereby preserving physical accuracy in the Fresnel region.

Third, spatial non‑stationarity (SNS) is introduced to model the element‑wise visibility and power variations that ELAA experiences; a visibility mask and per‑element power‑scaling function are generated for each cluster, reproducing the >10 dB power fluctuations reported in real‑world ELAA measurements. Fourth, a cluster‑count variability mechanism is added, allowing the number of multipath clusters to be drawn from a probability distribution rather than being fixed, which reflects the sparsity of multipath in the upper‑mid band.

The tutorial then walks the reader through the practical implementation of these features. It starts with the baseline Geometry‑Based Stochastic Model (GBSM) flow defined in TR 38.901 Clause 7.5 (distance and frequency calculation, LOS/NLOS determination, LSP sampling, cluster generation, and small‑scale fading parameter extraction). It then details the extensions required by Rel‑19 (Clause 7.6), including: (1) applying spherical‑wavefront corrections to the delay and phase of each ray, (2) generating and applying the SNS visibility mask per antenna element, and (3) sampling the cluster‑count distribution for each channel realization. The authors provide pseudo‑code, parameter tables, and benchmark results that validate the implementation against the reference model.

Finally, the paper discusses remaining challenges. The added near‑field and SNS calculations increase computational complexity, making real‑time system‑level simulations more demanding. Integration with deterministic ray‑tracing tools is still limited, and the model does not yet cover integrated sensing and communication (ISAC) aspects such as radar cross‑section modeling. The authors suggest future research directions for Rel‑20, including extensions to sub‑THz frequencies, refined SNS statistical models, and machine‑learning‑based parameter estimation to reduce simulation overhead.

In summary, this tutorial bridges the gap between the Rel‑19 specification and practical simulation, enabling researchers and engineers to accurately model FR3 propagation with ELAA, evaluate 6G system performance, and identify open research problems for the next generation of mobile standards.