Secure MISO-NOMA Transmission With Artificial Noise

This correspondence studies a new secrecy beamforming (SBF) scheme for multiple-input single-output non-orthogonal multiple access (MISO-NOMA) systems. In particular, the proposed SBF scheme efficiently exploits artificial noise to protect the confidential information of two NOMA assisted legitimate users, such that only the eavesdropper's channel is degraded. Considering a practical assumption of the imperfect worst-case successive interference cancellation which is a unique character in employing NOMA transmission, we derive a closed-form expression for the secrecy outage probability to characterize the secrecy performance. After that, we carry out an analysis of secrecy diversity order to provide further insights about secure MISO-NOMA transmission. Numerical results are provided to demonstrate the accuracy of the developed analytical results and the effectiveness of the proposed SBF scheme.

I. Introduction

Non-orthogonal multiple access (NOMA), which efficiently exploits power domain multiplexing at transmitter(s) and successive interference cancellation (SIC) at receiver(s) to serve multiple users in the same resource block (e.g., time/frequency/code domain), has shown its promising potential to improve wireless spectrum efficiency [1]–[4]. Owing to the broadcast nature of radio frequency communications, the confidential information is vulnerable to passive eavesdropping, and thus, guaranteeing secure NOMA transmission by enlisting the help of physical layer security technique has attracted enormous research attention (see, e.g., [5]–[10] and references therein).