Artificial-Noise-Aided Secure Transmission in Wiretap Channels with Transmitter-Side Correlation

TL;DR

This paper investigates how transmitter-side correlation affects artificial-noise-aided secure transmission and proposes a correlation-based power allocation strategy that outperforms uniform allocation, especially with increasing antenna correlation.

Contribution

It introduces a correlation-based power allocation (CPA) method for artificial noise in secure transmission, with proven optimality in large systems and practical benefits for correlated antennas.

Findings

CPA nearly optimizes secrecy outage probability.

CPA significantly outperforms uniform power allocation.

Secrecy outage probability decreases with more correlated antennas using CPA.

Abstract

This work for the first time examines the impact of transmitter-side correlation on the artificial-noise-aided secure transmission, based on which a new power allocation strategy for artificial noise (AN) is devised for physical layer security enhancement. Specifically, we design a correlation-based power allocation (CPA) for AN, of which the optimality in terms of achieving the minimum secrecy outage probability is analytically proved in the large system regime with the number of transmit antennas approaching infinity. In order to fully reveal the benefits of the CPA, we derive easy-to-evaluate expressions for the secrecy outage probability achieved by the CPA. Our study demonstrates that the CPA is nearly optimal and significantly outperforms the widely-used uniform power allocation (UPA) even for a moderately small number of correlated transmit antennas. Furthermore, our numerical results reveal a fundamental difference between the CPA and UPA. That is when the number of correlated transmit antennas increases, the secrecy outage probability of the CPA always reduces while the secrecy outage probability of the UPA suffers from a saturation point.