Enhancing Content Caching in D2D Networks: A Stackelberg Game Approach with Wireless Energy Transfer and Social Awareness

In a cache-enabled device-to-device (D2D) network, cooperative D2D caching holds promise for reducing data traffic and overall waiting time. However, the act of content caching and transmission can impose a drain on battery power, thereby diminishing users' enthusiasm. In this study, we examine a D2D group wherein all D2D transmitters (D2D-TXs) collaborate to serve users alongside the utilization of wireless power transfer for charging D2D-TXs. We consolidate the cache capacities of all D2D-TXs into a single entity and formulate a unified caching policy. Additionally, we design an incentive power mechanism aimed at users with social consciousness to incentivize D2D-TXs. To meet users' quality of service (QoS) requirements, we employ the Poisson point process and a hexagonal grid model to assess the likelihood of successful content delivery from base stations (BSs) and D2D-TXs to a user situated at the center of the D2D group. Addressing users' waiting time constraints, we evaluate the cumulative waiting time using inter-contact and G/G/1 queueing models. A Stackelberg game framework is employed to resolve conflict between D2D-TXs and users. The objective is to achieve a Stackelberg equilibrium, wherein users minimize costs by establishing an incentive power benchmark based on their QoS, while D2D-TXs maximize utility through optimized content caching strategies. Simulation results demonstrate that cooperative caching, with equitable distribution of cached contents among D2D-TXs, yields lower total waiting time than non-cooperative caching. Furthermore, as user density, total cache size, and data skewness increase, our proposed caching scheme exhibits minimal total waiting time for D2D-TXs and users.