 of PRB grids, reference signals, etc. (see also Figure 3.5.2). Each SS/PBCH block in the time domain occupies four adjacent OFDM symbols and is transmitted over a maximum of 240 subcarriers, which corresponds to 20 PRBs. A detailed SS/PBCH structure is illustrated in Figure 3.5.5. In NR three sequences are used for PSS modulation, where each PSS conveys par- tial information on the physical cell identity. For PSS modulation, a maximum length sequence - often denoted as M-sequence - with three cyclic shifts is used instead of the Zadoff-Chu sequences in LTE in order to provide better autocorrelation properties under 3.5 NR Physical Layer Offset to first subcarrier Offset to carrier of the nearest PRB Offset to Point A Carrier bandwidth Figure 3.5.4 SSB position indication in frequency domain. Figure 3.5.5 NR SS/PBCH block 240 subcarriers structure. 144 subcarriers 127 subcarriers non-ideal synchronization assumptions. The SSS sequences in NR are also constructed based on M-sequences and convey information on the physical cell identity. More specif- ically, each SSS sequence is obtained by using a cyclic shift operation applied to the XOR function of two M-sequences. To support more dense deployments with larger number of cells, NR defines 1008 SSS sequences, which doubles the number of supported physical cell identities compared with LTE. During the initial phase of the UE connection to the cell, after detecting the PSS/SSS syn- chronization signals the UE also decodes the PBCH. The PBCH of NR carries the remaining critical information such as SS/PBCH block index, OFDM index, slot index, system frame number (SFN) index, etc., and has a payload of 56 bits including cyclic redundancy check (CRC). The transmission time interval for PBCH is 80 ms, allowing for soft combining of PBCH transmissions over multiple PBCH occasions. To assist the demodulation of PBCH, DM-RS are transmitted together with the PBCH. The DM-RS for PBCH has a regular comb structure and its density is three resource elements per PRB. The actual p