Designing Constant-Envelope Transmissions for Secret Communications in MISO Wiretap Channels

Abstract

We consider the synthesis of discrete finite-alphabet inputs for secure communications in multiple-input-single-output wiretap channels. We aim that the source with the synthesized transmissions can communicate with a legitimate receiver and degrade the performance of a potential eavesdropper. To this end, we formulate an optimization problem to minimize the Euclidean distance between the reference inputs and the synthesized inputs. We devise an iterative algorithm to tackle the non-convex design problem with constant-envelope constraints. Moreover, we extend the proposed methodology to deal with low peak-to-average-power ratio transmissions. The numerical examples demonstrate that the proposed algorithms can achieve the requirement of secrecy communications efficiently.