as well as with LTE-based LAA and other incumbent RATs to ensure compliance with regulatory requirements. 3GPP Rel- 15 NR introduced a flexible frame structure with various subcarrier spacing options and slot formats. It further introduced mini-slot configuration, whereby PDSCH resource allocation can start from almost any symbol in a slot. The NR-U is expected to support both baseline NR Type A (slot-based) and Type B (non-slot-based) resource allocation schemes. Even with restricted mini-slot length of 2, 4, and 7 symbols for downlink, the PDSCH transmis- sion (without gap) can still start at almost any symbol position, if we allow multiple mini- slots to be allocated within a slot. In the uplink, however, the mini-slot length and starting symbol are not restricted, thus uplink transmission in NR-U (without gap) can start at any symbol position. For sub-7 GHz unlicensed bands, 15 kHz SCS with normal cyclic prefix that was supported in LTE-based LAA and the same SCS must be supported in NR-U to achieve similar cover- age when the component carrier bandwidth is 20 MHz. On the other hand, if a larger SCS is 882 Chapter 8 used, the OFDM symbol duration will be shorter, which increases the channel access oppor- tunities, reduces latency, and enhances resource utilization. A larger SCS can facilitate sin- gle wideband-carrier operation. In carrier aggregation scenarios (similar to LTE-based LAA), the device performs LBT per component carrier and then transmits on any available component carrier. Operating a single carrier allows reducing the control overhead and avoiding the use of inter-carrier guard bands. For the same system bandwidth, a larger SCS requires a smaller FFT size, hence reducing the implementation complexity. The studies suggest that an NR system with SCS of 60 kHz operating as a wideband carrier obtains about 60% average downlink user throughput gain and 80% average uplink user throughput gain over LTE-based LAA system for the same system bandwidth [14,20]. The performance gain comes from the finer g