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 article 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 (PL), 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 (LOO) 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 multiband model. This article 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.