d OTDOA domain One transceiver unit and one Each antenna element or RF beam with high antenna antenna port has a Each RF beam has a transceiver unit gain (coverage) transceiver unit Figure 6.7. Beamforming architecture The main evolutions of the massive-MIMO mechanism compared to the traditional MIMO mechanism are provided in Table 6.1. Mechanism massive-MIMO Number of antenna 1, 2, 4, 8, 12, 16, 1, 2, 4, 8 1, 2, 4, 8, 12, 16 ports CSI-RS 20, 24, 28, 32 Number of RF chains 32-128 Number of antennas 16-32 128-256 Beam control Baseband Hybrid Vertical and horizontal Beamforming Horizontal plane 3D beam plane Number of RF signals SU-MIMO Number of RF signals 4 (note 1) 8 (note 2) 8 (note 2) MU-MIMO Note 1: the maximum number of spatially multiplexed mobiles is equal to 4. The number of radio signals per mobile is then equal to 2. Note 2: the maximum number of spatially multiplexed mobiles is equal to 8. The maximum number of radio signals per mobile is equal to 2. Table 6.1. Comparison between MIMO and massive-MIMO mechanisms 168 NG-RAN and 5G-NR 6.1.4. Antenna systems The transmission modes implementing beamforming and the MU-MIMO mechanism require good correlation between the antennas. The transmission modes implementing transmission diversity and the SU-MIMO mechanism require decorrelation between the antennas. For an antenna made up of columns of vertically polarized radiating elements, the correlation between the columns is relatively strong. For an antenna consisting of a column of two sets of radiating elements, each set corresponding to +45 degree cross-polarization, the correlation is relatively weak. The antenna configurations are described in Figure 6.8 and relate to a single frequency band. Configuration A corresponds to an antenna made up of a column of vertically polarized radiating elements. Configuration B corresponds to an antenna made up of two columns of vertically polarized radiating elements. Configuration C corresponds to an antenna made up of four columns of vertically polarized radiating elem