to 64 SS blocks can be transmitted. In that case, we need three extra bits where those bits are signaled explicitly in the PBCH payload. Now that we understand the details of an SS block structure, we will now provide a brief overview of the different channels that composed SS blocks. We will start with the PSS and the SSS. Physical channels and signals for the initial access procedure PSS and SSS PSS and SSS are mapped to 127 consecutive subcarriers in the first and third OFDM symbols in the SS block respectively. Their center frequency is aligned with the center frequency of the PBCH. PSS/SSS sequence 8 subcarriers 9 subcarriers frequency 142 143 Figure 5.11 - PSS and SSS mapping PSS is a 3 length 127 M sequences, and it is created by cyclic shifts of a basic M sequence. SS is 336 length 127 M sequences with the addition of two M sequences. The following figure represents how this sequencing works: x(n+7) x(n+6) x(n+5) x(n+4) x(n+3) x(n+2) x(n+1) Figure 5.12 - Sequencing After the detection of PSS and SSS, the device knows the PCI and the timing of the PBCH. Detection of SS Block and frequency Detection of SSS symbol timing Identification of cell ID (Nid,2 = 0,1,2) Cell Search Identification of cell ID group (N1, ID,1 = 0,1,...,335) => PCI Possible to read System Info Figure 5.13 - A cell search flow diagram 5G Air Interface and Physical Layer Procedures - Part 2 As described previously, PSS and SSS are used for cell search. The preceding figure represents the cell search flow diagram. The device first detects the SS block SCS and the frequency. Then, it gets the SSS symbol timing and the cell ID, which can be 0, 1, or 2. Later, the device detects the cell ID group that comes from SSS. Now, it is time to discuss the PBCH, which is the other part that composes the SS block. PBCH definition The PBCH is broadcasted as part of the SS block. This is the last channel that composes the SS block. Moreover, the PBCH, PSS, and SSS are transmitted on the same antenna port using a single antenna transmission scheme. Sample