he same time for further reduction of the modem power consumption. BWP is a key feature in 5G NR to resolve the modem power consumption issue for single wideband carrier operation. So far this section has mainly focused on the bandwidth adaptation in a single wide- band carrier. As of Release 15, in addition to single wideband carrier, 5G NR retains the LTE carrier aggregation for wide bandwidth operation. The BWP adaptation can therefore operate in each of the individual component carriers. Since a mobile device supporting a wideband carrier requires more advanced implementation of RF compo- nents, not every mobile device may have such capability, especially for early 5G NR deployments. Carrier aggregation is a well-known technique introduced in 4G LTE that can be exploited in some 5G NR device implementations to cover the same bandwidth as a wideband device but over multiple narrowband carriers, for example, aggregating five 20 MHz carriers for a total bandwidth of 100 MHz. Though component carrier activation/deactivation can be utilized to enable band- width adaptation for modem power consumption reduction, secondary carriers are rarely deactivated in real-life 4G LTE network deployments, due to the long activation time necessary to re-activate the secondary carrier (e.g. up to 34 ms in 4G LTE). In Rel-15 5G NR, the secondary carrier activation time is even slower than in 4G LTE (e.g. up to 90 ms) due to the sparser density of common pilots for modem automatic gain control (AGC) and synchronization. Take video streaming, for example; the data typically arrive in large packets inter- mittently, and therefore a second component carrier is often activated by the network to quickly deliver these packets. Most of the time in between these large packets, 13 5G Modem Design Challenges Sleep, 20% 1-carrier PDCCH only, 10% Data service, 10% 2-carrier PDCCH only, 60% Figure 13.16 Power consumption distribution for 4G LTE modem with two-carrier carrier aggregation in video streaming application. Low-power BWP Primary Car