Artificial-Noise Aided Secure Transmission in Large Scale Spectrum Sharing Networks

TL;DR

This paper analyzes how beamforming and artificial noise can enhance secure communication in large scale spectrum sharing networks, considering multiple eavesdroppers and primary user constraints, with new analytical expressions and asymptotic results.

Contribution

It provides a comprehensive analytical framework for assessing secrecy performance, including exact and asymptotic expressions, and reveals optimal power allocation strategies in large scale networks.

Findings

Equal power allocation is not always optimal for maximum secrecy.

Artificial noise's advantage diminishes with strong interference.

Derived exact and asymptotic secrecy performance metrics.

Abstract

We investigate beamforming and artificial noise generation at the secondary transmitters to establish secure transmission in large scale spectrum sharing networks,where multiple non-colluding eavesdroppers attempt to intercept the secondary transmission. We develop a comprehensive analytical framework to accurately assess the secrecy performance under the primary users' quality of service constraint. Our aim is to characterize the impact of beamforming and artificial noise generation on this complex large scale network. We first derive exact expressions for the average secrecy rate and the secrecy outage probability.We then derive an easy-to-evaluate asymptotic average secrecy rate and asymptotic secrecy outage probability when the number of antennas at the secondary transmitter goes to infinity. Our results show that the equal power allocation between the useful signal and artificial noise is not always the best strategy to achieve maximum average secrecy rate in large scale spectrum sharing networks. Another interesting observation is that the advantage of beamforming and artificial noise generation over beamforming on the average secrecy rate is lost when the aggregate interference from the primary and secondary transmitters is strong, such that it overtakes the effect of the generated artificial noise.