ic shifts in the PRACH preamble sequence set including index to logical root sequence table, cyclic shift Ncs, and set type, that is, unrestricted, restricted set A, or restricted set B. Physical random-access procedure is triggered following a request from the UE RRC sub- layer or by a PDCCH command (control element) with the following parameters [8]: con- figuration for PRACH transmission, preamble index, preamble subcarrier spacing, transmit power target PRACH' RA-RNTI, and a PRACH resource. The PRACH preamble is transmitted using the selected PRACH format with transmission power value over the designated PRACH resource. The SS/PBCH block indices are mapped to PRACH occasions (see Fig. 4.82); first, in increasing order of preamble indices within a single PRACH occasion followed by, in increasing order of frequency resource indices of frequency-multiplexed PRACH occasions, then, in increasing order of time resource indices of time-multiplexed PRACH occasions within a PRACH slot and, finally, in increasing order of indices of PRACH slots. The associ- ation period, starting from frame 0, for the mapping of SS/PBCH blocks to PRACH occasions New Radio Access Physical Layer Aspects (Part 2) 619 PRACH slot PRACH slot PRACH slot PRACH slot PRACH-Preamble PRACH PRACH configuration period SSBO SSB 1 SSB 2 SSB 3 Rach-Preamble PRACH SSB SSB 1 SSB 2 SSB 3 PRACH slot i PRACH slot it One PRACH occasion Figure 4.82 Structure of NR PRACH opportunities in time and frequency domain 14]. Table 4.29: Mapping between PRACH configuration period and SS/PBCH block to PRACH occasion association period [8]. PRACH Configuration Association Period (Number of PRACH Period (ms) Configuration Periods) {1,2,4,8,16} {1,2,4,8} {1,2,4} {1,2} is the smallest value in a set (see Table 4.29) determined by the PRACH configuration period such that NSSB TX SS/PBCH blocks are mapped at least once to the PRACH occasions within the association period. A UE obtains the parameter NSSB TX from SystemInformationBlockType1. If after an integer number of SS/PB