4 and if we adopt RB-based interlace Nsc = 12 to satisfy 80% of the minimum OCB requirements, the maximum number of permissible interlaces would be N = 2. For some NR bandwidth and SCS combinations, due to regulatory requirements and design constraints, the number of interlaces available 890 Chapter 8 Interlace 0 for UE 0; PTX=P Interlace 1 for UE 1; PTX P 24 PRBs Interlace 0 Interlace 1 Interlace 0 for UE 0; PTx = 2P Interlace 2 for UE 1; PTX = 2P Interlace 2 Interlace 3 24 PRBs 20 PRBs Figure 8.27 RE-group-level interlace design [35]. (A) Uniform RB level interlace. (B) Uniform RE group level interlace. (C) Nonuniform RE-group level interlace. per symbol can be very limited; in such cases, RE-group-level interlace schemes may be utilized (see Fig. 8.27). In Rel-15 NR, five PUCCH formats are defined, where PUCCH formats 0 and 2 are short PUCCH formats which occupy up to two OFDM symbols; PUCCH formats 1, 3, and 4 are long PUCCH formats which occupy between 4 and 14 OFDM symbols. For PUCCH for- mats 0 and 1, the number of UCI bits is 1 or 2, whereas, for PUCCH formats 2, 3, and 4, the UCI bits can be very large. For PUCCH formats 2 and 3, the maximum number of occu- pied PRBs is 16, whereas PUCCH formats 0, 1, and 4 use only one PRB. Considering the use of LBT and the regulatory requirements on OCB, NR-U makes special considerations about UCI payload size and transmission efficiency as well as UE multiplexing capacity. To overcome the uncertainty of LBT and to improve the spectral efficiency in the unli- censed band, the network may schedule uplink transmission of multiple UEs within the same channel occupancy time. However, due to the OCB requirement, the number of inter- laces per symbol may be limited. As described earlier, a larger SCS value leads to a more restrictive interlace design. Operation in Unlicensed and Shared Spectrum 8.2 Network Architecture and Protocol Aspects In the previous section, we described the prominent methods that cellular industry has con- sidered for access to the unlicensed spectru