essed by 21.9 - 6.8 PLtw = + (11.7) 11.2 Propagation Measurements Above 6 GHz Tx Antenna docomo Measurement Building Rx Antenna Horn Antenna Angles +50 deg. Courtyard -180 deg. -180 deg. -50 deg Figure 11.23 Channel sounding setups for outdoor-to-indoor scenario. Here, the values of 21.9 and 6.8 represent the upper limit and lower limits, respectively. The RMS value of the residual error is 6.8 dB. Note that it has been confirmed that the frequency dependence of PLtw, is very small in this measurement. 11.2.4.2 Measurement of Channel Model Parameters The channel sounding for the outdoor-to-indoor (O2I) scenario was performed in the campus of Niigata University, Niigata, Japan, as shown in Figure 11.23 [6, 15]. In the mea- surement, the Tx of the channel sounder was located at points B2, B3 with an antenna height of 2.5 m. On the other hand, the Rx of the channel sounder was located in the building. Measurement data were acquired in the corridors on the 1st, 2nd, 4th, 6th, and 8th floors (namely, 1F, 2F, 4F 6F, and 8F) with positions 2, 9, and 16 m from the glass windows. The height of the horn antenna was 1.5 m. Here, at each Rx position, the horn antenna was rotated, and the PDPs were measured. The ranges of rotation varied from - 180° to + 180° with a 1° step for the azimuth angle, and from -50° to +50° in 10° steps for the elevation angle. Table 11.8 shows the measurement results for the outdoor-to-indoor (O2I) scenario. Here, the K-Power-Mean method was used to cluster multipath channels. The delay times, azimuth angles, and elevation angles of the cluster centroids were used to obtain the DS, ASA, and ZSA at each position. Table 11.8 Measurement results for outdoor-to-indoor scenarios. # of rays Cluster Cluster Cluster Floor positions positions (m) (deg.) (deg.) paths clusters per cluster DS (ns) ASA (deg.) ZSA (deg.) 102.0 104.8 151.6 129.0 123.6 log10 -7.29 Cross-correlations ASA vs. DS ZSA VS. DS ZSA VS. 11 Measurements Field Experiments with Sub-6-GHz 5G Radio 11.3.1 Experimental System with Higher Rank 