he reference signal on different subcarriers, or by using the OCC code on the same subcarriers (see Table 4.8). Orthogonality in code is such that the scalar product of two codes is zero. 4.5.2.2.2. Physical PT-RS signal The physical PT-RS signal is defined by the following formula: rk =r(2M+k'), with r being the DM-RS. The PT-RS is optional, the terminal is informed of the presence of the PT-RS during radio link reconfiguration (RRC signaling) via the timedensity parameter carried by the PTRS-DownlinkConfig data structure. The physical PT-RS is a copy of the DM-RS; it should not be mapped to the resource elements used for the DM-RS and CSI-RS physical signals. In the time domain, the PT-RS is repeated every L symbols, taking the DM-RS as reference. 5G-NR Radio Interface - The Physical Layer In the frequency domain, the PT-RS is transmitted with a density of one RB out of 2, or one RB out of 4. 4.5.2.2.3. The physical DM-RS signal associated with the PDCCH channel Associated with the PDCCH, the DM-RS is a Gold sequence generated by the following formula: with c(n) as the Gold sequence extracted from the following two M-sequences: = mod x,(n+31)=(x,(n+3)+x,(n))mod2 X2(n+31)=(x2(n+3)+x2(n+2)+x2(n+1)+ x2(n))mod 2 = At the start of each subframe, the initial value Cinit of the pseudo-random sequence is calculated from the following formula: n's as the slot number in the frame and 1 as the position of the slot OFDM in the slot. The parameter "ID corresponds to the identity of the PCI cell. The PCI is calculated by the mobile at the end of the time synchronization, or can be provided by the RRC layer via the pdcch_DMTS_ScramblingID parameter. The mapping to the resource elements (k, 1), with k as the subcarrier and 1 as the symbol number, is defined by the following formula: k=12n+4k'+1 with k'=0,1 or 2. The reference point corresponds to the first subcarrier on which the set of CORESET control resource elements (Control RE Set) are transmitted. This information is transmitted to the terminal in an SIB message, or duri