All the user equipment (UE) functionalities used by the 3GPP 5G specifications are defined as UE features and these are being mandatory and optional, or mandatory with optional capability. These UE features are subject to UE capability signaling and are captured in TS 38.306 [49], while features that do not have capability signaling and corresponding capability definition in TS 38.306 are by definition mandatory. This chapter presents a glimpse of some of the mandatory physical layer parameters. The parameter names are as defined by the TS 38.306 [49]. While most of the parameters are applicable to both FR1 and FR2, it is mentioned explicitly that there are situations in which parameters are applicable only to one of the frequency ranges.