ot on both at the same time. In the case of SUL, the UE is configured with two uplink carriers in conjunction of one downlink carrier of the same cell, and uplink transmissions on those carriers are controlled by the net- work to avoid colliding uplink control and traffic channels in time domain. The colliding transmissions on uplink traffic channel are avoided through scheduling while overlapping transmissions on uplink control channel are avoided via limiting configuration of uplink control channel on only one of the two uplink carriers. In addition, initial access is sup- ported on each of the uplink carriers. To improve uplink coverage for high-frequency sce- narios, a low-frequency SUL carrier can be configured. In NR, the UE can take advantage of the bandwidth adaptation feature to save power while satisfying the requirements of vari- ous services/applications. The network can configure up to four BWPs for each UE, and dynamically send change indications to the UEs as required. The BWP switching for a serving cell is used to activate an inactive BWP or to deacti- vate an active BWP at any given time, as shown in Fig. 3.51. The BWP switching is controlled by the PDCCH indicating a downlink assignment or an uplink grant, by the bandwidthPartInactivityTimer, or by the MAC entity itself upon initiation of random- access procedure. Upon addition of a Special Cell (SpCell)22 or activation of an SCell, one BWP is initially active without receiving PDCCH indicating a downlink assignment or an uplink grant. The active BWP for a serving cell is indicated by either RRC or PDCCH. For paired spectrum, a downlink BWP is paired with an uplink BWP, and BWP switching applies to both uplink and downlink [20]. The BWP switching options are illustrated and compared in Fig. 3.52. 3.7.3 Resource Allocation One of the main design objectives for signaling the resource allocation information, in the form of a set of resource blocks in each slot, to the active UEs in the cell is to find a bal- anced tradeoff between flexibility and 