are used instead. The aforementioned structure is used over each of the OFDM symbols and a length-2 orthogonal sequence is used to extend the code-domain separation over time, resulting in up to eight orthogonal sequences. The DM-RS Type 2 has a similar structure to Type 1, except some differences with to the number of antenna ports that are supported. Each CDM group for Type 2 consists of two neighboring subcarriers over which a length-2 orthogonal sequence is used to separate the two antenna ports sharing the same set of subcarriers. Four subcarriers are used in each resource block and in each CDM group. Since there are 12 subcarriers in a resource block, up three CDM groups with two orthogonal reference signals can be created using one resource block over one OFDM symbol. If a second OFDM symbol is used along with a length-2 sequence in time-domain, up to 12 orthogonal reference signals can be generated [14]. The location of front-loaded DM-RS symbols, which can be either one or two symbols, is dependent on whether a slot based (DM-RS mapping Type A) or non-slot-based (DM-RS mapping Type B) scheduling is used. In the former type, fixed OFDM symbols regardless of the PDSCH assignment are used to map DM-RS (configurable via parameter lo = {2,3}), whereas in latter type which corresponds to mini-slots, the first OFDM symbol assigned for PDSCH is used to map DM-RS. The reference point for l and the position lo of the first DM-RS symbol depends on the mapping type. Additional DM-RS symbols can be configured (e.g., for high-speed scenarios) as well as for broadcast/multicast PDSCH. In the preceding equations, the reference point for frequency index k depends on PDSCH payload. The reference point for frequency index k is subcarrier 0 of the lowest numbered resource block in CORESET 0, if the corresponding PDCCH is associated with CORESET 0 and Type0-PDCCH common search space and identified by system informa- tion (SI)-RNTI; otherwise, it is the subcarrier 0 in common resource block 0. Furthermore, the reference point