I. Introduction
5th Generation Mobile Communication Systems (5G) and B5G (Beyond 5G) systems will be used in a wide range of applications such as Internet of Things (IoT) in addition to the conventional high-speed Internet access for content downloading [1]. However, in future IoT systems, higher uplink speed will be required for video content transmission for monitoring applications, for example. In addition, higher microwave and millimeter wave bands will be widely used in 5G/B5G systems, thus power utilization efficiency of the HPA (High Power Amplifier) needs to be improved in addition to spectrum efficiency [bit/s/Hz] for battery-operated mobile terminals [2].