New Radio Access Physical Layer Aspects (Part 2) 429 CSI-RS period = 5 slots, offset = 0 CSI-RS period = 5 slots, offset = 3 slots CSI-RS period= 10 slots, offset = 3 slots Time (Slots) Figure 4.6 Example CSI-RS periodicity and offset [6]. CSI-RS-ResourceMapping information element [6,13]. The starting position and number of the resource blocks in which the CSI-RS is transmitted are provided via RRC signaling. The CSI-RS is transmitted on antenna ports p=3000+s+jLcDM where j=0,1,...,Np/Lcom 1 and s=0,1, LCDM 1. In the latter expression, LCDM e{1,2,4,8} is the CDM group size and Np is the number of CSI-RS antenna ports. The CDM groups are numbered in order of increasing frequency-domain allocation first and then increasing time domain-allocation. For a CSI-RS resource configured as periodic or semi-persistent by the RRC parameter resourceType, the CSI-RS is transmitted in slot num- bers satisfying (Nslot framenslot TCSI-RS where the CSI-RS periodicity TCSI-RS (in number of slots) and slot offset Toffset are signaled by the RRC parameter CSI-ResourcePeriodicityAndOffset or slotconfig (see Fig. 4.6). The CSI-RS is transmitted in a slot only if, all OFDM symbols of that slot corresponding to the configured CSI-RS resource are designated for downlink transmission. The antenna ports within a CSI-RS resource are quasi-co-located with quasi-co-location (QCL) Type A, Type D (when applica- ble). In summary, the NR supports periodic, aperiodic, semi-persistent CSI-RS transmission. The NR CSI-RS patterns can be mapped to 1, 2, or 4 OFDM symbols and support CDM2, CDM4, CDM8 spreading functions, for example, CDM8 means that there are eight spread- ing functions wf(k') and wt(l'). For CSI acquisition, the NR supports CSI-RS density =0.5 and 1 RE/RB/port and a PRB-level comb-type transmission. The number of antenna ports can be independently configured for periodic, aperiodic, semi-persistent CSI reporting. A CSI-RS resource configuration up to 32 ports is supported in NR. The UE-specific CSI-RS may be configured to support wide