rier 100 MHz Low-power BWP High-performance BWP Secondary Carrier Low-power BWP 100 MHz High-performance BWP Low-power BWP Figure 13.17 Example illustration of BWP operation in contiguous carrier aggregation. however, there is little traffic activity while the modem continues performing PDCCH monitoring for both carriers. Figure 13.16 shows the power consumption breakdown for a 4G LTE modem with two-carrier carrier aggregation in a video streaming scenario. In this example, the secondary carrier is activated only for PDCCH monitoring in most of the use time. In 5G NR, the power consumption issue with carrier aggregation can be even more severe because the bandwidth of each component carrier can be larger than that of 4G LTE. For non-contiguous carrier aggregation in 5G NR, different RF chains are applied for each carrier SO the techniques of bandwidth adaptation and PDCCH monitoring period- icity adaptation in each carrier are beneficial for reducing the modem power consump- tion. However, for contiguous carrier aggregation, as shown in Figure 13.17, a single RF chain is applied to both carriers, and only the technique of PDCCH monitoring period- icity adaptation is useful for modem power consumption reduction. Therefore, even for carrier aggregation, BWP is also a key feature in Rel-15 5G NR to resolve the modem power consumption issue for carrier aggregation. However, as mentioned earlier, the 5G NR modem should be designed to reduce the additional energy required for turning on/off of function blocks for more frequent on/off transitions. 13.5.3 Impacts on Modem Design Though the modem power consumption issue can be resolved by the support of BWP operation in 5G NR, it does not come for free. BWP operation introduces at least the following two modem impacts: High modem processing capability to support 2-3 ms switching delay for DCI-based active BWP switching 13.5 Wider Bandwidth Operation and Modem Power Consumption Active BWP switch by DCI Slotn-2 Slot, Slot, Slot, n+2 Slotn+ Slotn+4 DCI processing Layer 1 pro