eration. The SRS transmission should also meet the OCB require- ments; thus NR-U can only support wideband and BWP/subband SRS transmission. In LTE-based LAA revisions, downlink and uplink transmissions start and end at certain points. More specifically, using frame structure type 3, a downlink or uplink transmission can start at slot boundaries. Because LBT may end at any time which is not necessarily aligned with the symbol boundaries, the interval between the end of LBT and the start of a PDCCH/PUSCH transmission may be wasted. The partial ending subframe reduces over- head by defining more ending points, that is, OFDM symbol positions 2, 5, 8, 9, 10, 11, and 13 for the downlink and 6, 12, and 13 for the uplink can be used as partial subframe ending Operation in Unlicensed and Shared Spectrum Starting position 1: symbol 1 Starting position 2: 012345678910111213 symbol 3 Starting position 3: 012345678910 symbol 5 Starting position 4: 012345678910111 symbol 7 Starting position 5: symbol 8 Starting position 6: 0123456789 symbol 10 Starting position 7: 012345678910 symbol 12 2 Symbol minislot 4 Symbol minislot 7 Symbol minislot Figure 8.24 Flexible starting point with nonuniform minislot patterns [33]. points. The NR-U provides more frequent start/end points than LTE-based LAA allowing more flexible transmission as shown in Fig. 8.24. As we mentioned earlier, LBT is a spectrum sharing mechanism that can operate across dif- ferent RATs. However, it suffers from the hidden node and the exposed node problems. These issues arise when the coverage of the nodes in a network are different. The problem worsens when the sensing and transmit coverages are different. This may occur when an omnidirectional antenna pattern is used for carrier sensing whereas a directional antenna (or array) pattern is used for transmission, resulting in a higher node exposure likelihood. In the example depicted in Fig. 8.25, device A senses the carrier using omnidirectional antenna pattern and overhears the transmission from device C to D. Dev