BER analysis of non-orthogonal multiple access-based cognitive butterfly network

In this Letter, the non-orthogonal multiple access (NOMA) technique is applied to the cognitive butterfly network, where a secondary relay assists a primary transmitter-receiver pair in the lack of a direct link between them to realise spectrum sharing for a secondary transmitter-receiver pair. In this network, the uplink and downlink NOMA principles are combined and the side information from the nearer transmitters is exploited for better successive interference cancellation (SIC) at the receivers. The end-to-end bit error probability (BEP) is analytically derived for both users and the results are approved via computer simulations by considering imperfect SIC. The better BEP performance provided by NOMA compared to a reference orthogonal multiple access protocol is demonstrated.