 and uplink transmissions to take place on the same carrier frequency; thus the concept of beam correspondence is also applicable to FDD systems in paired spectrum. The beam management is defined as the process of acquiring and maintaining a set of beams, which are originated at the gNB and/or the UE and can be used for downlink and uplink transmission and reception. The beam management process comprises the following functions as shown in Fig. 4.43 [11]: Beam sweeping: Covering a spatial area with a set of beams transmitted and received according to prespecified intervals and directions. The measurement process is carried out with an exhaustive search, that is, both UE and the base station have a predefined codebook of directions (each identified by a beamforming vector) that cover the entire angular space and are used sequentially to transmit/receive synchronization and refer- ence signals. New Radio Access Physical Layer Aspects (Part 2) 511 SS bursts TRP-level beam Sweeping for coverage SS blocks to obtain RACH resources UE selects the best TRP and UE TX/RX Beam aquisition UE receives RACH resource allocation RACH preamble UE-specific beam selection and beam forming Figure 4.43 Signals and messages exchanged during downlink beam management procedure [69]. Beam measurement: Evaluation of the quality of the received signal at the gNB or at the UE. Different metrics may be used for this purpose such as SNR, which is the aver- age of the received power on synchronization signals divided by the noise power. The measurements for the initial access are based on the SS blocks. The tracking is done using the measurements conducted on the SS bursts and the CSI-RSs, which include a set of directions that may cover the entire set of available directions based on the UE requirements. Beam determination: Selection of the suitable beam or beams either at the gNB or at the UE, according to the measurements obtained via the beam measurement procedure. This process further allows the TRP(s) or the UEs to select their own trans