On the Performance of Transmit Antenna Selection for Physical-Layer Security of NOMA Systems Under Untrusted Users

In this paper, the physical layer security for a two-user downlink NOMA cluster, between a near trusted user and a far untrusted user, subject to Nakagami- m fading is investigated. It is considered an scenario with a multiple antenna base station, in which the antenna with best channel for the near user is selected. The pair outage probability and secrecy outage probability are analyzed to verify the system performance gain. Results show improvements in the pair outage probability and secrecy outage probability when the relative distance between the trusted user and the BS decreases, its link has direct line of sight and/or the number of base station antennas increases.