 smartphone usage and then identifies the key challenges that have to be overcome in 5G NR to maintain the same level of user experience while deliv- ering a 20-fold increase in data rate. Section 13.5.2 focuses on bandwidth adaptation, which is one of the primary features introduced in NR to address power consumption issues. Finally, the impacts of implementing these features on modem design are given in Section 13.5.3. 13.5.1 Modem Power Consumption in Daily Use The power consumption of a modem results both from the design of the modem itself and from the semiconductor manufacturing process used to physically implement it. Advances in semiconductor manufacturing processes have played an important role in improving the power efficiency of modems. Undoubtedly these have contributed to the phenomenal success of 4G LTE. However, as the physical limitations of the process node are being reached, SO are the limitations of the corresponding power efficiency gains. The 20-fold increase in data rate presents a major challenge for modem design. In the following, this issue is introduced from the perspective of existing 4G LTE design based on which 5G NR conclusions are then drawn. Based on extensive field logging, it is found that the modem power consumption accounts for less than 20% of the total day of use (DoU) power consumption of an LTE smartphone. The remaining power consumption comes from the device's screen, graph- ics processing unit (GPU), AP, and SO on, Focusing on the modem only, Figure 13.11 shows the use time and power consumption of a typical LTE modem throughout a DoU. In these pie charts: 4G operation, including Data Service and Voice Service, refers to the modem state in which there is data traffic for the modem to process. 13 5G Modem Design Challenges 4G operation, Data Service, PDCCH only, 23.0% 33.0% Voice Service Standby, 17.0% Sleep, 27.0% Use Time Distribution Power Consumption Distribution Figure 13.11 Example DoU for 4G LTE modem using 20 MHz. Standby, including PDCCH-only and Sleep, refers to 