On the Physical Layer Security of a Dual-Hop UAV-based Network in the Presence of per-hop Eavesdropping and Imperfect CSI

TL;DR

This paper analyzes the physical layer security of a dual-hop UAV network with imperfect CSI and mobility, deriving closed-form secrecy intercept probability expressions and revealing the impact of system parameters on security performance.

Contribution

It provides the first analytical expressions for secrecy intercept probability in UAV networks considering imperfect CSI and mobility effects, highlighting the influence of various system parameters.

Findings

Zero secrecy diversity order under mobility with imperfect CSI.

Linear drop in intercept probability at high SNR with perfect CSI.

Secrecy loss increases with node speed, frequency, delay, and relay SNR threshold.

Abstract

In this paper, the physical layer security of a dual-hop unmanned aerial vehicle-based wireless network, subject to imperfect channel state information (CSI) and mobility effects, is analyzed. Specifically, a source node $(S)$ communicates with a destination node $(D)$ through a decode-and-forward relay $(R)$, in the presence of two wiretappers $\left(E_{1},E_{2}\right)$ independently trying to compromise the two hops. Furthermore, the transmit nodes $\left(S,R\right) $ have a single transmit antenna, while the receivers $\left(R,D,E_{1},E_{2}\right) $ are equipped with multiple receive antennas. Based on the per-hop signal-to-noise ratios (SNRs) and correlated secrecy capacities' statistics, a closed-form expression for the secrecy intercept probability (IP) metric is derived, in terms of key system parameters. Additionally, asymptotic expressions are revealed for two scenarios, namely (i) mobile nodes with imperfect CSI and (ii) static nodes with perfect CSI. The results show that a zero secrecy diversity order is manifested for the first scenario, due to the presence of a ceiling value of the average SNR, while the IP drops linearly at high average SNR in the second one, where the achievable diversity order depends on the fading parameters and number of antennas of the legitimate links/nodes. Furthermore, for static nodes, the system can be castigated by a $15$ dB secrecy loss at IP$=3\times10^{-3},$ when the CSI imperfection power raises from $0$ to $10^{-3}$. Lastly, the higher the legitimate nodes' speed, carrier frequency, delay, and/or relay's decoding threshold SNR, the worse is the system's secrecy. Monte Carlo simulations endorse the derived analytical results.