elements at mmave frequencies. Aside from a higher directional gain, these antenna types offer com- plex beamforming capabilities. This allows increasing the capacity of cellular networks by improving the signal-to-interference ratio through direct targeting of user groups. The nar- row transmit-beams simultaneously lower the amount of interference in the radio propaga- tion environment and make it possible to maintain sufficient signal power at the receiver terminal at larger distances in rural areas. An important prerequisite for any beamforming architecture is a phase coherent signal, which means that there is a defined and stable phase relationship between all RF carriers. A fixed phase offset between the carriers can be used to steer the main antenna lobe to a desired direction. A major difference between NR and LTE is the support for beamformed control channels, which resulted in different reference signal design for each control channel. The NR physical channels and signals, including those used for control and synchronization, have all been designed to support beamforming. The CSI for operation with a large number of antennas can be obtained via CSI reports from the devices based on transmission of CSI-RSs in the downlink, as well as using uplink measurements exploiting channel reciprocity. 4.1.9.3.1 Analog Beamforming Analog beamforming typically relies on conditioning the amplitude and phase of the sig- nals that feed the antenna array. The combination of these two factors is used to improve sidelobe suppression or steering nulls. Phase and amplitude for each antenna element are combined by applying a complex-valued weighting factor to the signal that is fed to the New Radio Access Physical Layer Aspects (Part 2) 565 2-Antenna linear array 4-Antenna linear array Analog beam steering by phase shifting 8-Antenna linear array 16-Antenna linear array (-30°, 0°, +30° phase shift and 8 antennas) Digital stream baseband RF processing processing Phase shifter + PA Figure 4.63 Analog beamforming transmitter arch