4 GHz to 28 GHz Coherent Channel Measurements and Spatial–Time Comparative Analysis for 6G Green Networks

6G mobile networks currently face the critical challenge of minimizing energy consumption in network operations. To tackle this, the hyper-cellular network model, or fully-decoupled radio access networks, has been proposed. In these networks, control base stations (BSs) use low-frequency bands, while data BSs rely on high-frequency bands. A comprehensive analysis of spatial-time domain characteristics and interactions between these bands is essential for effective implementation. This paper presents data from channel measurements obtained during urban micro-cell (UMi) field studies, which involve simultaneous, co-located measurements at 4 GHz, 6.8 GHz, 13 GHz, and 28 GHz using a channel sounder with a 400 MHz bandwidth and multi-antenna active arrays. The extracted spatial-time domain characteristics include power delay profiles, pathloss, delay spread, and angular spectrum, alongside an assessment of spatial and frequency consistency. These results aim to guide the future deployment of decoupled 6G networks.