Abstract
This paper investigates secure transmission in unmanned aerial vehicle (UAV) relay-assisted millimeter wave (mmWave) networks, where the selected UAV relay performs secure transmission in both the on-off and non-on-off schemes. Meanwhile, there are multiple eavesdroppers randomly distributed on the ground and attempting to wiretap the transmission. Leveraging the air-to-ground channel model and the tools of stochastic geometry, the novel expressions of transmit probability (TP) and secrecy outage probability (SOP) are derived in both the on-off and non-on-off transmission schemes with perfect beam alignment. The secrecy performance improvement is demonstrated in the on-off transmission scheme, and we find that there exists an optimal altitude of UAV relays to achieve the best TP. In addition, due to the limitations of UAV carriers, such as its low computational capacity and high mobility, the perfect beam alignment is difficult to achieve in the mmWave networks aided by UAV relays, and the effect of beam alignment error on the secrecy performance is investigated in the considered networks. Analyzing the numerical and simulation results, we find that the SOP will not have obvious deterioration when the beam alignment error is relatively small, and the SOP can be improved by using the antennas with a large number of elements. However, in high beam alignment error regime, the antenna arrays with a smaller number of elements will provide the better SOP.
Highlights
Millimeter wave has attracted considerable research attention due to its plentiful available spectrum resources [1,2,3]
We consider that the uniform planar square antenna is adopted at each node, the antenna element number of the S, unmanned aerial vehicle (UAV) relays, D and eavesdroppers are denoted as Nl, l ∈ {S, R x, D, Ee }, and the main-lobe beamwidth, the antenna gain of the main lobe and side lobe of an
We investigate secure transmission in UAV relay-assisted mmWave networks where the beam alignment is achieved or not
Summary
Millimeter wave (mmWave) has attracted considerable research attention due to its plentiful available spectrum resources [1,2,3]. The mmWave communication links are prone to outage, especially in an environment with dense blockage, e.g., a mountainous area To this end, deploying the unmanned aerial vehicle (UAV) relays in the air has been investigated for performance improvement and disconnection recovery in the mmWave networks [4,5]. The performance improvement can be obtained by employing the UAV relays, it makes the transmission vulnerable to eavesdroppers due to the inherent broadcast of the wireless networks. As such, it is one of the key concerns to provide a secure communication in UAV relay-assisted mmWave networks. We focus on secure on-off transmission in UAV relay-assisted mmWave networks
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