Secure transmission design in cooperative NOMA networks: Orienting toward user requirements

This paper presents a full‐duplex and multi‐antenna relay‐aided transmission scheme for the user‐oriented perspective in cooperative non‐orthogonal multiple access (NOMA) systems. Relying on the service requirements, two legitimate users with security demands (SU) and quality of service (QoS) demands (QU) are paired for NOMA execution. The security of SU is enhanced through inverse power allocation of the conventional NOMA. The QoS requirements for QU are guaranteed, simultaneously. Then, the precoding design at the multi‐antenna relay has been exploited to improve the reliability demands of SU. Closed‐form expressions for SU's outage probability (OP) and intercepted probability, as well as QU's OP, are derived. The security–reliability trade‐off is also presented. Additionally, performance analysis under the half‐duplex and multi‐antenna scheme is provided as a benchmark for comparison. Finally, numerical simulations are performed to confirm the accuracy of the theoretical derivations under different schemes. Results demonstrate the superiority of the proposed scheme over benchmark schemes in terms of improving the security and reliability of SU, as well as saving power consumption of the system.