e- domain using different orthogonal sequences. The DM-RS corresponding to PUSCH for antenna ports 2 and 3 belong to CDM group 1 and are generated in the same way using odd-numbered subcarriers which are separated in the code domain. If more than four New Radio Access Physical Layer Aspects (Part 2) orthogonal antenna ports are needed, two consecutive OFDM symbols are used. The above DM-RS structure is used over each OFDM symbol and a length-2 orthogonal sequence is applied across time, resulting in up to eight orthogonal sequences. DM-RS Type 2 has a similar structure as Type 1; however, there are some differences, most notably the number of antenna ports supported. As shown in Fig. 4.74, each CDM group for DM-RS Type 2 consists of two neighboring subcarriers over which a length-2 orthogonal sequence is applied to separate the two antenna ports sharing the same set of subcarriers. Two such pairs of subcarriers are used in each resource block for one CDM group. Since there are 12 subcarriers in a resource block, up to three CDM groups each with two orthogonal reference signals can be created using one resource block over one Group-0 >AP-0 Group-0 Group-1 Group-1 Group-2 Single-symbol Type 2 DM-RS Single-symbol Type 1 DM-RS Group-0 Group-0 Group-1 Group-1 Group-2 Group-0 Group-0 Group-1 Group-1 AP-10 Group-2 AP-11 Double-symbol Type 2 DM-RS Double-symbol Type 1 DM-RS Figure 4.74 Illustration of DM-RS Type-1 and Type-2 time-frequency-code structures [14]. 596 Chapter 4 OFDM symbol. The number of Type 2 DM-RSs can be increased up to 12 by applying a length-2 orthogonal sequence across time domain. While the basic structures of DM-RS Type 1 and Type 2 are similar, the frequency-domain density of DM-RS Type 1 is higher than that of Type 2; however, Type 2 provides a larger number of orthogonal patterns, which useful for MU-MIMO use cases. The type of the reference signal structure is deter- mined by dynamic scheduling and higher layer configuration. 4.2.2.1.2 PUCCH DM-RS The DM-RS sequence for PUCCH format 1 is define