ction of the radio channel. The received SRS is also used to measure the quality of the radio link (CSI). The CSI measurement is used by the base station for the sequencing and adaptation of the specific link to the UE. In TDD, by exploiting the channel reciprocity, the transmitter can estimate the downlink channel from the sounding on the uplink channel. The SRS physical signal, configured at the mobile level, is limited to four antenna ports. The SRS signal is a CAZAC Zadoff-Chu sequence. A cyclic shift in the time domain (phase rotation of the Zadoff-Chu sequence) allows the physical SRS to be multiplexed between each antenna port. The position in the time domain of the SRS is located in the last six symbols of the slot (symbol 8 to symbol 13) and is spread over one, two or four consecutive OFDM symbols (see Figure 4.19). The SRS position is defined by 1=13-10,fset with loffsel={0,1,2,3,4,5}. The frequency location of the SRS forms a comb: the mobile uses a subcarrier on KTC, KTC, taking the value 2, 4 or 8 (see Figure 4.19). KTC=2 KTC=4 KTC=4 Figure 4.19. SRS signal mapping (one or two symbols) The SRS signals transmitted by different mobiles are multiplexed in the frequency domain. If KTC=2, two SRS can be multiplexed; if KTC = 4, four SRS can be multiplexed. 4.6.1.2. The DM-RS signal associated with the PUSCH channel The physical DM-RS signal is transmitted with the PUSCH signal. The same precoding is applied to the PUSCH channel and DM-RS channel to help the receiver to demodulate the signal, without needing to know the precoding matrix used for the data. NG-RAN and 5G-NR Associated with the PUSCH, the DM-RS is either a Gold sequence or a CAZAC sequence, depending on the shape of the signal (OFDM or DFT-S-OFDM, respectively). When the DM-RS associated with the PUSCH is based on DFT-S-OFDM modulation, the DM-RS reference sequence is a CAZAC sequence generated by the formula: At the start of each subframe, the initial value Cinit of the pseudo-random sequence is calculated from the following formula: When th