-RS 0; otherwise, kref NRNTI mod(NRB mod KPT-RS). The parameter NRNTI is the RNTI associated with the DCI that is used to schedule PUSCH [6]. Example time-frequency mapping of CP-OFDM uplink PT-RS is depicted in Fig. 4.75. New Radio Access Physical Layer Aspects (Part 2) 601 4.2.2.3 Sounding Reference Signal A UE can be configured to transmit SRS in order to enable the gNB to estimate the uplink channel. Similar to the downlink CSI-RS, the SRS can serve as QCL reference for other physi- cal channels such that they can be configured and transmitted quasi-co-located with SRS. As a result, if the knowledge of a suitable receive beam for the SRS is available, the receiver would know that the same receive beam should be suitable for other physical channels. The SRS sup- ports up to four antenna ports, and it is designed to have low cubic metric, enabling efficient operation of the high-power amplifier. In general, the SRS can span one, two, or four consecu- tive OFDM symbols and is located within the last six symbols of a slot. In the frequency domain, an SRS occasion has a comb structure where the SRS is transmitted on every Nth sub- carrier where N = 2 or 4, referred to as comb-2 or comb-4. The SRS transmissions from dif- ferent devices can be frequency-multiplexed within the same frequency range using different comb patterns corresponding to different frequency offsets. For comb-2, that is, transmitting SRS on every other subcarrier, two SRSs can be frequency multiplexed, whereas for comb-4, up to four SRSs can be frequency multiplexed. Fig. 4.76 illustrates example SRS multiplexing assuming a comb-2 structure spanning two OFDM symbols. The sequences used to represent a set of SRS are based on Zadoff-Chu sequences. A Zadoff-Chu sequence is a complex-valued sequence with constant amplitude property whose cyclically shifted versions exhibit low cross-correlations. Thus under certain conditions, the cyclically shifted versions of each sequence remain orthogonal to one another. A Zadoff-Chu sequence that has not been s