Distributed content placement in cache-enabled small cell networks in the presence of malicious users

Caching popular files at the edge of wireless networks has been proved to be an effective strategy to reduce the content delivery delay and alleviate the backhaul congestion. However, due to the vulnerability of the edge networks to malicious threats, it is essential to investigate security-aware caching strategies which can combat mischievous content requesting processes. These processes may defeat the whole purpose of edge caching by deliberately issuing requests incompatible with the known popularity distribution. In this paper, we investigate the content placement problem in cache-enabled Small Base Stations (SBSs) to minimize the downloading delay of contents. We consider that some users’ requesting behavior may become compromised by an adversary and thus may not follow the known statistics of the content popularity . We formulate the problem using the notion of a multi-leader single-follower Stackelberg game between the SBSs and the adversary. The objective of each SBS is to minimize the congestion duration of the backhaul links and the average delay of the users within its coverage range, whereas the adversary aims at maximizing the congestion duration of the backhaul links by generating fictitious requests for non-cached files. Using the standard notion of a potential function in game theory, we propose an iterative algorithm that is provably convergent toward the Stackelberg equilibrium of the formulated game. Simulation experiments are conducted to validate the convergence of the proposed algorithm as well as to evaluate its performance under different mixed populations of malicious/non-malicious users.