ly high. But if the amplifier gain is relatively low, the amount of power that is needed to drive the input of the amplifier should be considered in a metric that measures the efficiency of the said amplifier. 724 Chapter 5 Table 5.15: Impact of NR features on UE key components' power consumption [25]. 5G Features Antenna RF Front- RF Integrated Baseband Application Tuning Unit Circuit Processing Processor [Scalable] Bandwidth UL-MIMO High-power UE Bandwidth part Discontinuous reception Cross-slot scheduling Multiple PDCCH monitoring occasions Measurement System information acquisition Paging RAN-based notification area update characteristic. The relationship between the efficiency and power consumption can be given as PAE = (POUT - PIN)/ = (POUT - PIN)/(Vdcldc). There are many parameters affecting the efficiency of the PA including backoff power, load line loss, topology, etc. For a typical load line, the loss is between 0.3 and 0.7 dB, which means it will degrade the PAE by 7%-15%. Another factor affecting the efficiency of the PA is the backoff power. For the topology of traditional linear PAs, for example, Class-A/Class-AB/Class-F, the PAE decease when the backoff from the peak power increases. There are several methods for improving the efficiency of the PAs including the following [25]: Average power tracking (APT): This is a technique that can be utilized to adapt the sup- ply voltage to a PA on a timeslot basis in order to reduce power consumption of the PA. In APT method, the supplied voltage of the PA is adjusted according to output power level SO that the linearity of the PA is maintained while the efficiency is improved. Although limited by the speed of the DC-DC converter, the APT voltage must be kept constant in each time slot, which means the efficiency cannot be improved, if the PA constantly operates at the highest power. Envelope tracking (ET): The ET is a power supply adaptation technique that maximizes the energy efficiency by keeping the PA in compression mode over the entire transmis- sion c