Physical Layer Security in Uplink NOMA Multi-Antenna Systems With Randomly Distributed Eavesdroppers

The physical layer security of uplink non-orthogonal multiple access (NOMA) is analyzed. A stochastic geometry approach is applied to analyze the coverage probability and effective secrecy throughput (EST) of the kth NOMA user, where a fixed or an adaptive transmission rate can be used. We consider a protected zone around the legitimate terminals to establish an eavesdropper-exclusion area. We assume that the channel state information associated with eavesdroppers is not available at the base station. We also consider that the base station is equipped with multiple antennas. The impact of imperfect successive interference cancellation is also taken into account in this paper. Our framework allows to compute, numerically, the wiretap code rates that maximize the EST. In addition, our framework also allows an optimum selection of other system parameters, such as the transmit power or the eavesdropper-exclusion radius.