The interplay between the non-orthogonal multiple access (NOMA) and the opportunistic
cognitive radio (CR)-based orthogonal frequency multiple access (OFDMA) has been
recently realized as a promising paradigm to support the unprecedented massive
connectivity demands of future beyond fifth-generation (B5G) wireless communication
systems. In such systems, which are called multi-carrier NOMA CR-based systems, each
licensed band reserved for primary users can be opportunistically utilized based on power …