Power-Aware User Association and Content Caching Algorithm for Delay-Energy Tradeoff in Cache-Enabled Heterogeneous Cellular Networks

A large number of devices communicating through the backhaul links in heterogeneous cellular networks (HetCNets) will incur severe traffic congestion, high delay, and huge energy consumption. Enabling caching capabilities has been regarded as a promising way to reduce the high-delay pressure of file delivery on the backhaul links. However, file delivery has different requirements on quality-of-service, and the increased densification of small base stations will consume more energy, thus it is essential to solve the problem of delay and energy in cache-enabled HetCNets. In this article, we employ a utility function with the weighted sum of energy consumption and delay cost to formulate the delay-energy tradeoff optimization problem that is a kind of multiobjective optimization problem. Considering a jointly performed mechanism comprising power control, user association, and content caching, the optimization problem is further decomposed into the primal problem and the main problem by generalized Benders decomposition method. Here, the primal problem is related to power-aware user association that dynamically associates with the base station, and the main problem is related to content caching. Furthermore, an iterative power-aware user association and content caching algorithm (PAUA-CC) is proposed. Finally, we present numerical simulation results to demonstrate the effectiveness of our proposed approach on the optimal delay-energy tradeoff.