iplexing for multi-port CSI-RS 110 NG-RAN and 5G-NR The reference signals per resource block and antenna port are multiplexed into: - frequency (FDM: Frequency Domain Multiplexing), the reference signal occupies a resource element on a subcarrier of the resource block, and the CSI-RS signals for all of the antenna ports are distributed over the resource block without interfering; - time (TDM: Time Domain Multiplexing), the reference signal occupies one resource element on one symbol per slot, and all of the CSI-RS signals are distributed over the duration of a slot; - code (CDM: Coding Domain Multiplexing), the same time and frequency resources are used for several antenna ports (2, 4 or 8) thanks to an Orthogonal Cover Code (OCC), which allows us to proceed to the separation of the signals reference at the receiver side. The OCC code = Wf * Wt is defined by Table 4.8, according to the number of antenna ports (2, 4 or 8). Index i defines the code for the i-th antenna port. 10 11 12 13 2 ports FDM 2 ports TDM CSI-RS user 1 CSI-RS user 3 CSI-RS user 2 CSI-RS user 4 4 ports CDM Figure 4.9. CSI-RS multiplexing multi-ports 4.5.2.2. Physical DM-RS and PT-RS signal The DM-RS signal transmitted by the gNB base station on the downlink is associated with either the PDSCH channel, the PDCCH channel or the PBCH channel. 4.5.2.2.1. Physical DM-RS signal associated with PDSCH channel The physical DM-RS signal is precoded with the same code as the PDSCH data. On the reception side, the DM-RS helps the receiver to estimate the channel and 5G-NR Radio Interface - The Physical Layer 111 apply an equalization to the PDSCH signal, without needing to know the precoding matrix used for the data. Associated with the PDSCH channel, the DM-RS is a Gold sequence generated by the following formula: * with as a Gold sequence calculated from the following two M-sequences: (x,(n+Nc)+x2(n+N))1 = mod (n+31) =(x(n+3)+x,(n)) = mod 2 x2(n+31)=(x2(n+3)+x2(n+2)+x2(n+1)+x2(n))mod = At the start of each subframe, the initial value Cinit of the pseudo-