On the Secrecy Performance of Continuous-Aperture Arrays Over Fading Channels
This work addresses security in wireless communication for scenarios with eavesdroppers, but it is incremental as it extends existing analysis to continuous-aperture arrays.
The paper analyzes the secrecy performance of continuous-aperture array (CAPA) systems in wiretap channels under Rayleigh fading, deriving expressions for secrecy rate and secrecy outage probability across scenarios with single, multiple independent, and multiple collaborative eavesdroppers, and shows that CAPA systems achieve higher secrecy rates and lower secrecy outage probabilities compared to spatially-discrete array systems.
The secrecy performance of continuous-aperture array (CAPA)-based wiretap channels in terms of secrecy rate and secrecy outage probability (SOP) is analyzed. First, the system models of CAPA systems with maximum-ratio transmission under a Rayleigh fading channel are established, and approximate probability density functions for the legitimate user Bob's signal-to-noise ratio (SNR) and the eavesdropper Eve's SNR are derived using Mercer's theorem and Landau's eigenvalue theorem. Three scenarios are considered, including a single Eve, multiple independent Eves, and multiple collaborative Eves. Next, the expressions of the secrecy rate and SOP under these three scenarios are derived, and the high-SNR slope, high-SNR power offset, diversity order, and array gain in Bob's high-SNR region are obtained. It is then theoretically proven that, in all three scenarios, the CAPA system achieves the same high-SNR slope and the same diversity order, with the latter being equal to the spatial degrees of freedom. Moreover, the CAPA system with a single Eve has the smallest high-SNR offset and the highest array gain, whereas the CAPA system with multiple collaborative Eves exhibits the largest high-SNR offset and the lowest array gain. Finally, the theoretical analyses of secrecy rate, SOP, high-SNR performance are validated by the simulation results, and a higher secrecy rate and a lower SOP are achieved by the CAPA systems compared to the spatially-discrete array systems with half-wavelength antenna spacing.