Blind Receiver Design for Downlink Cognitive-Radio NOMA Networks

Non-orthogonal multiple access (NOMA) and cognitive radio (CR) are two promising technologies that provide efficient spectrum utilization, which is required for future wireless networks to support heterogeneous user requirements. In this work, we study the throughput performance of a downlink CR-NOMA network comprising a primary user (PU) and a secondary user (SU). Considering a blind cognitive SU which receives its packets opportunistically in an uncoordinated manner, the base station adapts the transmission mode (TM) to satisfy the users' bit error rate quality of service requirements. The network falls under the hybrid underlay-interweave paradigm, and it is considered uncoordinated since SU does not receive frequent signalling about current TM. This keeps the overhead signalling at minimum levels and maintains the spectral-efficiency. The obtained numerical results show that the proposed network can provide substantial throughput improvement over conventional NOMA networks, even when considering non-ideal cognitive receiver in block fading or frequency selective fading channels.