cessing RF Tuning BWP 1 Active BWP Switching Time Figure 13.18 Modem processing timeline of DCI-based active BWP switching for 15 kHz subcarrier spacing. Figure 13.18 illustrates the modem processing timeline of DCI-based active BWP switching for 15 KHz subcarrier spacing. From Figure 13.18, the overall active BWP switching delay consists of three major parts: (1) DCI processing, (2) Layer 1 process- ing, and (3) RF tuning. Among the three parts, layer 1 processing accounts for the largest portion of the overall active BWP switching delay because it involves the calculation of many detailed baseband and RF parameters due to BWP configuration switching, and there is a trade-off between the processing time and modem hardware cost. Though a modem's radio interrupts during the active BWP switching delay in Rel-15 5G NR, only RF tuning actually requires radio interruption. Since a longer radio interruption time introduces a larger user throughput degradation, it may prevent frequent use of active BWP switching for better modem power efficiency if the modem radio interrup- tion time is equal to the active BWP switching delay. This is another aspect for further enhancements in future 5G NR releases. In addition to modem power consumption, carrier aggregation also introduces other modem impacts, including at least the following: High modem processing capability for PDCCH blind decoding to support a large number of carriers Great difficulty for a modem to support short secondary carrier activation time with sparse common pilots (e.g. SS/PBCH block) for AGC settling and synchronization In Rel-155G NR, up to 16 carriers can be supported in carrier aggregation. The greater the number of carriers supported in carrier aggregation, the more overall PDCCH blind decoding candidates are introduced and the higher the modem processing capability needed to meet the timeline for HARQ operation and UL scheduling supported in R15 5G NR. Though there are several techniques supported in Rel-15 5G NR to prevent an excessive number of overa