In this paper, we investigate for the first time the benefits of wirelesscaching for the physical layer security (PLS) of wireless networks. Inparticular, a caching scheme enabling power-efficient PLS is proposed forcellular video streaming with constrained backhaul capacity. By sharing videodata across a subset of base stations (BSs) through both caching and backhaulloading, secure cooperative transmission of several BSs is dynamically enabledin accordance with the cache status, the channel conditions, and the backhaulcapacity. Thereby, caching reduces the data sharing overhead over thecapacity-constrained backhaul links. More importantly, caching introducesadditional secure degrees of freedom and enables a power-efficient design. Weinvestigate the optimal caching and transmission policies for minimizing thetotal transmit power while providing quality of service (QoS) and guaranteeingsecrecy during video delivery. A two-stage non-convex mixed-integeroptimization problem is formulated, which optimizes the caching policy in anoffline video caching stage and the cooperative transmission policy in anonline video delivery stage. As the problem is NP-hard, suboptimalpolynomial-time algorithms are proposed for low-complexity cache training anddelivery control, respectively. Sufficient optimality conditions, under whichthe proposed schemes attain global optimal solutions, are also provided.Simulation results show that the proposed schemes achieve low secrecy outageprobability and high power efficiency simultaneously.
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