Comprehensive FR3 and FR1(C) upper-mid band propagation and material penetration loss measurements and channel models in Indoor environment for 5G and 6G

Wide bandwidth requirements for multi-Gbps communications have prompted the global telecommunications industry to consider new mid-band spectrum allocations in the 4--8 GHz FR1(C) and 7--24 GHz FR3 bands, above the crowded bands below 6 GHz. Allocations in the lower and upper mid-band aim to balance coverage and capacity, however, there is limited knowledge about the radio propagation characteristics in the 4--24 GHz frequency bands. Here we present the world's first comprehensive propagation measurement study at 6.75 GHz and 16.95 GHz in mid-band spectrum conducted at the NYU WIRELESS Research Center spanning distances from 11--97 m using 31 dBm EIRP transmit power with 15 and 20 dBi gain rotatable horn antennas at 6.75 GHz and 16.95 GHz, respectively. Analysis of the omnidirectional and directional path loss using the close-in free space model with 1 m reference distance reveals a familiar waveguiding effect in indoor environments for line-of-sight (LOS). Compared to mmWave frequencies, the omnidirectional LOS and non-LOS (NLOS) PLEs are similar, when using a close-in 1m free space path loss reference distance model. Observations of the omnidirectional and directional RMS delay spread (DS) at FR1(C) and FR3 alongside mmWave and sub-THz frequencies indicate a decreasing trend at higher frequencies. The RMS angular spreads (AS) at 6.75 GHz are found to be wider compared to 16.95 GHz showing greater number of multipath components from a broader set of directions are found in the azimuthal spatial plane compared to lower frequencies. This work also presents results from extensive material penetration loss measurements using ten common materials found inside buildings and on building perimeters, including concrete walls, low-emissivity glass, wood, doors, drywall, and whiteboard at co- and cross-polarized antenna configurations at both 6.75 and 16.95 GHz. Our findings show an increasing trend of penetration loss with frequency for all of the ten materials and partitions tested, and suggest revisions of 3GPP material penetration loss models for infrared reflective (IRR) glass and concrete may be necessary. The empirical data and resulting models for propagation and penetration presented in this paper provide critical information for future 5G and 6G wireless communications.