Interference Exploitation for Secure Communications: Error Rate and Secrecy Analysis

Interference exploitation has recently been shown to provide significant security benefits in multiuser communication systems. In this technique, the known interference is designed to be constructive to the legitimate users and disruptive to the malicious receivers. Accordingly, this paper analyzes the secrecy performance of constructive interference (CI) precoding technique in multi-user multiple-input single-output (MU-MISO) systems with phase-shift-keying (PSK) signals and in the presence of multiple passive eavesdroppers. The secrecy performance of CI technique is comprehensively investigated in terms of symbol error probability (SEP), and secrecy sum-rate. Firstly, new and exact analytical expressions for the average SEP of the legitimate users and the eavesdroppers are derived. Departing from classical Gaussian rate analysis, we employ finite constellation rate expressions to investigate the secrecy sum-rate. In this regard, closed-form analytical expression of the ergodic secrecy sum-rate is obtained. Then, based on the new secrecy sum-rate expression we revisit adaptive modulation (AM) scheme with the aim to enhance the secrecy performance. The numerical results in this work demonstrate that, the interference exploitation technique achieves a significant performance gain over the interference suppression schemes. Furthermore, the proposed AM scheme provides significant improvement in terms of the secrecy sumrate.