Physical Layer Security in Large-Scale Probabilistic Caching: Analysis and Optimization

Edge caching is proposed to offload traffic from backhaul links by storing popular contents on edge servers and reusing these pre-cached contents to meet the frequent requests from local users. Due to the limited computing and caching resources of edge servers, the traditional encryption and decryption technologies, deployed in the upper layers of protocol stacks, appeared difficult in providing secure content delivery for the growing number of mobile users. In this letter, we consider the physical layer security issues for the popular probabilistic caching. Unlike most prior works, which are concentrated on maximizing achievable transmission rate, we analyze the average secure delivery probability of the caching network and jointly optimize the redundant rate and caching probabilities. Simulation results are identical with the theoretical ones and the outperformance over existing caching strategies is observed with the optimal caching probability derived in this letter.