On The Performance of Multi-Carrier SDMA-NOMA CR-Based Systems

Recently, several multiple access (MA) have been proposed to support the massive connectivity of the cognitive radio (CR) internet-of-things IoT-based networks. Among these MA techniques, the combination of spatial domain multiple access (SDMA) and non-orthogonal multiple access (NOMA), namely SDMA-NOMA, shows a potential capability to meet the unprecedented massive connectivity requirements. With this SDMA-NOMA approach, both spatial and power domains offered by NOMA and SDMA, respectively, are utilized together to serve the secondary users (SUs) in CR networks. To further increase the number of connected SUs, a multi-carrier SDMA-NOMA CR-based system is considered in this paper. With this approach, the available bandwidth of transmission is divided into a set of sub-channels, in which an SDMA-NOMA CR-based transmission is utilized. To explore the benefits of this multi-carrier SDMA-NOMA system over the existing conventional MA techniques, a power minimization (P-Min) problem is formulated. With this P-Min problem, the total transmit power is minimized subject to achieve a set of quality-of-service (QoS) constraints. Simulation results show that the proposed multi-carrier SDMA-NOMA CR system outperforms the conventional approaches in terms of the total required power for transmission.