A hierarchical caching strategy in content delivery network

Abstract This paper considers a hierarchical content delivery network in a randomly distributed interference environment, where the caching capability is distributed among two layers, the caching nodes and part of users. We propose a hierarchical caching strategy that is jointly optimized with the delivery performance, to achieve a fine balance between the cooperative gain and the caching diversity gain. In particular, to guarantee the effectiveness of caching strategy, the impact of communication interference at different layers on caching strategy is discussed during the file delivery phase. The optimization problem to maximize the offloading probability is formulated as a combinatorial optimization problem. By breaking the problem into two sub-multiple choice knapsack problems, the extreme case in the absence of user caching ability is first analyzed, and an optimization method based on the worst-case among users is proposed. Detailed analytical analysis and simulation experiments are carried out to evaluate the proposed caching strategy. The experimental results prove the superiority of the proposed cache strategy by comparing it with other caching strategies.