Urban Macro/Microcellular Channel Characterization at 4.85 GHz With Literature-Referenced Upper-FR1-to-FR3 Cross-Band Analysis

Abstract

The transition from 5G to 6G requires frequency-dependent, physically consistent radio channel models across the upper-FR1/FR3 transition region, particularly in the underexplored 4--8 GHz region targeted in the current WRC-27 studies, where outdoor urban channel measurements and characterizations remain scarce. This paper presents a 4.85 GHz measurement-anchored study of urban channels and a literature-referenced cross-band analysis. Double-directional measurements were conducted at 4.85 GHz in urban macrocell (UMa) and urban microcell (UMi) routes in Yokohama, Japan, from which path loss, delay spread (DS), azimuth spread of arrival/departure (ASA/ASD), K-factor, and route-dependent spatial-consistency statistics were extracted. To align these results in a broader cross-band context, the measured 4.85 GHz large-scale parameter (LSP) means were combined with scenario-matched literature anchors to derive log-log trends for DS, ASA, and ASD over an approximately 4--28 GHz range around the 7.125 GHz upper-FR1/FR3 cross-band boundary. The resulting trends were compared with 3GPP UMa/UMi reference parameterizations over the same interval, and the sensitivity of the UMi DS fit was examined via leave-one-out analysis. Because the cross-band analysis still relies on a single in-house measurement band alongside heterogeneous anchors from different campaigns, it is presented as measurement-informed and indicative rather than as a definitive multi-band model. The paper therefore contributes both a detailed, parameterized 4.85 GHz urban measurement reference and a bounded literature-referenced view of channel behavior near the upper-FR1/FR3 transition