rtitioning model Full connection model TXU / TRU TXU / TRU TXU/TRU TXU / TRU Figure 6.6. Mapping models between TXU/TRU units and the antenna elements The weighting vector is implemented at the radio frequency signal level to beam the signal in a given direction. The Observed Time Difference Of Arrival (OTDOA) angle estimation method measures the signal reception power on each radiating element. ESPRIT (Estimation of Signal Parameters via Rotational Invariance) or MUSIC (Multi-Signal Classification) algorithms are the most used to define the angle of arrival. The advantage of this method is that it does not require information about the transmission channel. Active antenna systems control the beam in an analog (RF) way. 8 to 16 TXU/TRU radio frequency channels are connected to 16-32 radiating elements. The massive-MIMO mechanism corresponds to the increase in the number of M antennas, far greater than the number of K antennas of a UE mobile: 32, 64 and 128 TXU/TRU radio frequency chains are connected to 128, 192 and 256 radiating elements. The massive-MIMO 32T32R, 64T64R and 128T128R include 32, 64 and 128 RF channels (TXU/TRU), respectively. The massive-MIMO makes it possible to combine beam generation by digital coding and improves coverage by a connecting network of analog antennas. The hybrid architecture makes it possible to couple the techniques of baseband multiplexing (MIMO, beamforming) with an analog beam orientation to provide antenna gain (better coverage). The digital architecture is simpler to implement in the FR1 band. 5G-NR Radio Interface - MIMO and Beamforming The analog architecture is optional in the FR1 band; however, it is mandatory in the FR2 band. Frequency band Frequency band TXRU-1 TXRU-1 TXRU-2 TXRU-2 Analog BB BF BB BF Analog B beams B beams TXRU-B TXRU-B Digital (baseband) Analog Beamforming Beamforming Hybrid Beamforming Adaptative TX/RX weights at RF to form a beaming Adaptative TX/RX weights at Adaptative TX/RX weights at function of arriving signal baseband both analog and baseban