Physical Layer Security Performance Based on 3D Heterogeneous Network.

The distribution of the base stations (BSs) and users is mostly designed as a two-dimensional model in the study about heterogeneous networks (HetNets), which is not suitable for ultra-dense network scenarios. Meanwhile, the eavesdroppers existing in vertical dimension directly reduce the physical layer security of the HetNets. To tackle the mentioned problem, we propose to adjust the vertical dimension of the full-dimension (FD) antenna placed in the BSs; then the signal-to-noise ratios (SNRs) of the legitimate users and eavesdroppers are given due to the tilted angle. According to the three-dimensional Poisson point process (PPP) of BSs and users, the cumulative distribution function of SNR is deduced, which derives the closed expression of average security rate. The simulation results verify the correctness of the closed expression and the feasibility of proposed scenarios that the physical layer security performance can be improved by adjusting the vertical tilt angle. And density ratio of the BSs can be obtained in the various specific scenes.