Research on Physical Layer Security of NOMA System with Passive Eavesdropping

This paper investigates the performance of NOMA users collaborative communication system, where there exists a passive eavesdropper that try to eavesdrop the information of center user. A new cooperative NOMA scheme is proposed, in which center user can act as relays to assist cell-edge user in forwarding signals, while cell-edge user employs full-duplex technology to send interference signals to the eavesdropper, which improves the security of communication links and the quality-of-service (QoS). The legitimate receiver decodes the various signals from the superposition signals by successive interference elimination (SIC) technology. The closed expressions of the security outage probability and outage probability of two users are derived respectively under the condition that the wiretap channel statistics channel state information (CSI) is known, and it is verified by Monte Carlo simulation. Both the theoretical analysis and numerical simulations show that the performances of cooperative NOMA scheme are better than the non-cooperative scheme.