As we edge closer to 6G, the mid‑band spectrum between 7 and 24 GHz has emerged as a linchpin for future capacity and coverage. Until now, the 3GPP TR 38.901 channel model has been the industry benchmark for frequencies from 0.5 up to 100 GHz, underpinning system‑ and link‑level simulations for everything from urban microcells to indoor factories. However, a significant measurement gap remained in the 6–24 GHz range precisely where next-generation networks are expected to thrive.
Why the 7–24 GHz Update Was Necessary
While TR 38.901 nominally supports 0.5–100 GHz, over 80% of the empirical data it was based on was from sub‑6 GHz and mmWave bands above 24 GHz. The 6–24 GHz range had to rely heavily on interpolation, especially for parameters like delay spread, angular spreads, and penetration losses.
But this range—particularly near 6–8 GHz and 15 GHz—is key for early 6G deployment due to its balance of bandwidth and propagation. Moreover, new architectural trends such as large MIMO arrays, distributed TRPs, and near-field beamforming exposed technical gaps in the existing model. These challenges made the case for a dedicated Rel‑19 study and targeted model updates, formalized under the 3GPP Study Item RP‑234018.
The Rel‑19 Study Item
Launched in December 2023, this study preceded the official start of 6G discussions (from August 2025 at RAN1#122). It pursued two tracks:
Validation Track: Evaluate the suitability of existing TR 38.901 models for 7–24 GHz.
Extension Track: Introduce new modeling features where needed.
All technical agreements and contributions from RAN1#121 meeting when the study was officially closed are summarized in R1‑2504703 and R1‑2504756. The model updates were captured in Change Request (CR) R1‑2504964, which now amends TR 38.901 for Rel‑19.
Moreover, further maintenance discussions of the model continued at RAN1#122 meeting. The discussions are summarized in Feature Lead (FL) summary R1-2506405 and in the new endorsed CR R1-2506543 with further changes to TR 38.901.
Finally, at RAN1#122 the calibration of the models was concluded, and the results can be found in the TDoc R1-2506406 and in the public 3GPP FTP folder.
What’s New in TR 38.901
The update significantly extends both the empirical grounding and modeling capabilities of the TR 38.901 framework. Here’s a breakdown of the key additions:
1. Scenario Validation and Parameter Updates
Existing deployment scenarios—Urban Microcell (UMi), Urban Macrocell (UMa), Indoor Office (InH), and Indoor Factory (InF)—have been validated and recalibrated for the 7–24 GHz band. This includes updated parameters for delay spread, angular spreads (AoA, AoD, ZoA, ZoD), and outdoor-to-indoor penetration.
A significant part of this effort was a validation and data-driven re-fitting of all large-scale parameters, based on new and legacy measurements and ray-tracing results. The full 0.5–100 GHz range was split into three segments: below 6 GHz, 6–24 GHz, and above 24 GHz. Each segment was equally weighted in the parameter fitting process to ensure balanced calibration. The methodology, documented in R1‑2504960 and R1‑2504913, ensures model continuity across the full frequency span, including overlapping bands and boundary transitions.
2. New Suburban Macrocell (SMa) Scenario
A new scenario was introduced to model realistic suburban deployments (ISDs of 1200–1800 m), with dedicated LOS probability functions, O2I penetration models, and terrain effects like foliage. The update includes revision for common building materials such as plywood and glass, improving the accuracy of penetration loss modeling.
3. Advanced UE Antenna Modeling
The update introduces much more realistic UE models for both handheld and CPE devices:
Defined 3D form factors with realistic array sizes (e.g., 15×7 cm for handheld).
Directional UE antenna patterns with polarization and gain characteristics.
Configurable element placement with blockage effects due to head and hand.
Support for modeling per-port gain imbalances.
4. Optional High-Fidelity Propagation Features
Several new modeling capabilities are available optionally to support advanced 6G use cases:
Intra-cluster delay and angular spreads that vary with bandwidth and array size.
Absolute Time of Arrival modeling, critical for multi-TRP deployments across UMi, UMa, RMa, and SMa.
Near-field propagation modeling with spherical wavefronts, necessary for dense antenna deployments at short ranges.
Spatial non-stationarity, enabling element-wise variation in received power or fading statistics across large antenna arrays. Spatial non-stationarity is introduced both at the BS and UE sides.
Dynamic cluster behavior, including variability in number of clusters and power fluctuations between polarizations.
Finally, CDL channel model extension for MIMO that describes the scaling of angles procedure was corrected and clarified.
Looking Ahead
With Rel‑19 frozen and TR 38.901 updated, system designers and researchers now have a validated, high-fidelity channel model that spans the full 0.5–100 GHz range—now with realistic, scenario-specific behavior for the all-important 7–24 GHz band. The model not only corrects legacy gaps but equips the industry with tools to simulate 6G-era challenges like new UE antenna models, near-field beamforming, massive MIMO, polarization diversity, and spatial non-stationarity with much greater confidence.
In addition to 3GPP Study Item materials a few academic publications are under preparation and will be added as references below upon their availability:
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