h in a sense that the higher the bandwidth, the lower the PT-RS density. For the smallest band- widths, no PT-RS is transmitted. To reduce the risk of collision between PT-RS associated with different devices scheduled on overlapping frequency-domain resources, the subcarrier number and the resource blocks used for PT-RS transmission are determined by the C- RNTI of the device. The antenna port used for PT-RS transmission is given by the lowest numbered antenna port in the DM-RS antenna port group. An example time-frequency PT- RS structure is shown in Fig. 4.4. The PT-RS for subcarrier k is given by r PT-RS(k) = I'DM-RS(2m + K') where is the DM-RS at time-domain position lo and subcarrier k. The PT-RS is present only in the resource blocks used for the PDSCH, and only if there is an explicit indication of their pres- ence. In that case, the PT-RS is scaled by a factor of BPT-RS(i) to adjust the transmission power. The PT-RS is mapped to resource elements a(k, 1) = if l is located within the OFDM symbols allocated for the PDSCH transmission and the designated resource element is not used for DM-RS, CSI-RS, SS/PBCH block, PDCCH, or is declared as not available. The time indices l at which PT-RS are allocated are defined relative to the start of the PDSCH allocation lo and are given by l = lo + iLPT-RS where i is incremented as long as the PT-RS occasion falls inside the PDSCH allocation and the aforementioned conditions are met. For PT-RS resource mapping, the resource blocks allocated for PDSCH transmission are numbered from 0 to NRB - 1 from the lowest scheduled resource block to the highest. The corresponding subcarriers in this set of resource blocks are numbered in increasing order start- ing from the lowest frequency to NRB NRB 1. The subcarrier indices that the PT-RS are New Radio Access Physical Layer Aspects (Part 2) 425 PDSCH data PDSCH PDSCH data PT-RS on every OFDM symbol PT-RS on every second OFDM symbol PT-RS on every fourth OFDM symbol PT-RS on every second resource block PT-RS on every fourth resou