Caching popular contents is a promising way to offload the mobile datatraffic in wireless networks, but so far the potential advantage of caching inimproving physical layer security (PLS) is rarely considered. In this paper, wecontribute to the design and theoretical understanding of exploiting thecaching ability of users to improve the PLS in a wireless heterogeneous network(HetNet). In such network, the base station (BS) ensures the secrecy ofcommunication by utilizing some of the available power to transmit a pre-cachedfile, such that only the eavesdropper's channel is degraded. Accordingly, thenode locations of BSs, users and eavesdroppers are first modeled as mutuallyindependent poisson point processes (PPPs) and the corresponding file accessprotocol is developed. We then derive analytical expressions of two metrics,average secrecy rate and secrecy coverage probability, for the proposed system.Numerical results are provided to show the significant security advantages ofthe proposed network and to characterize the impact of network resource on thesecrecy metrics.
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