Opportunistic Multicast NOMA with Security Concerns in a 5G Massive MIMO System

This article concentrates on the multicast service in massive MIMO systems, and develops a hierarchical security model-based opportunistic NOMA scheme for 3D massive MIMO channel. In the considered scenario, the base station communicates with different security level users, where eavesdroppers are randomly deployed. Different security level users are classified into NOMA users and non-NOMA users, where NOMA users employ successive interference cancellation to cancel the low security multicast interference and separate their own data streams. The proposed scheme employs multicast beamforming in the multicast group, and applies null-space-based interference cancellation to eliminate the signal leakage generated by other groups. Numerical results revealed that hierarchical security model-based opportunistic NOMA schemes can significantly improve the network throughput and secrecy capacity in typical massive MIMO scenarios.