Bridging FR1 to FR3: Frequency-Continuous Urban Macro/Microcellular Channel Parameterization Anchored at 4.85 GHz

Abstract: The transition from 5G to 6G requires radio channel models that are frequency-continuous across the entire FR1--FR3 span, particularly in the under-explored 4--8 GHz region targeted by WRC-27. Existing 3GPP-style models are often specified at discrete frequencies, introducing discontinuities in large-scale parameters (LSPs) at the 7.125 GHz boundary. To address this, we develop a unified framework anchored by rigorous double-directional measurements at 4.85 GHz in three representative UMa/UMi layouts. We derive route-specific statistics for path loss, delay and angular spreads, K-factor, and spatial consistency using robust distance-binning and bootstrap processing. Subsequently, we construct a log-log frequency-continuous LSP model spanning 4.85 to 28 GHz by anchoring these local statistics to complementary high-frequency datasets. The resulting models ensure smoothness across 7.125 GHz and systematically deviate from 3GPP trends, capturing weaker dispersion in urban macrocells (UMa) and stronger frequency-dependent compaction in urban microcells (UMi). The proposed parameter set fills the measurement gap around 4.85 GHz and provides a practical, implementation-ready basis for wideband 5G/6G simulations, mobility evaluation, and spectrum-planning activities across the FR1--FR3 interface.