 as shown in Fig. 8.23. The number of PRBs for SS/PBCH blocks is 20 whereas the minimum number of PRBs for RMSI is 24. Using a 20 MHz bandwidth, the OCB requirement can be met if the numerology of SS/PBCH block and RMSI is set to 60 kHz. In that case, Pattern 1 can be considered for NR-U in the sub- 7 GHz bands. The TDM method in Pattern 1 allows the RMSI to provide consecutive transmissions between SS/PBCH blocks over the time span of DRS. In contrast, if 30 kHz SCS is selected, the bandwidth of SS/PBCH blocks would only be about 40% of a 20 MHz. In this case, a frequency division multiplex pattern such as Pattern 2 or 3 is preferred in terms of OCB requirement. When RMSI is multiplexed with SS/PBCH blocks using Pattern 2 or 3, the RMSI may not completely fill the gaps between the SS/ PBCH block transmissions. 886 Chapter 8 Pattern 1 Pattern 2 Pattern 3 Figure 8.23 Multiplexing patterns of SS/PBCH and RMSI transmission [33]. In NR-U, because a channel occupancy time can start at any time, the UE would need to perform frequent PDCCH monitoring, even when there is no downlink transmission intended for it. To solve this issue, a wake-up signal may be designed for NR-U to wake up the UE only when necessary. The transmission of a wake-up signal is also subject to LBT. To reduce the LBT overhead, the wake-up signal can be embedded in an existing signal such as DRS that is transmitted periodically, resulting in significant UE power saving while maintaining low signaling overhead. Similar to LTE, NR supports SRS-based frequency-selective scheduling and periodic/aperi- odic SRS transmission. NR also supports SRS-based downlink beamforming and semi- persistent SRS transmission, which are not supported in LTE. In NR-U, the transmission time of the SRS resource as well as the configuration of SRS resource and resource map- ping adapt to LBT and channel availability. Due to the uncertainty of channel availability, periodic SRS would not be feasible. The aperiodic SRS which is triggered by DCI has more flexibility for NR-U op