A novel coalition game based distributed cooperative content caching in mobile edge networks

In mobile edge networks with mobile vehicles, road-side units (RSUs) can be used as edge nodes to cache some popular contents for moving vehicles in advance, and therefore improving the transmission efficiency and quality of user experience during vehicle-to-infrastructure (V2I) content communication. Transferring large files to a fast-moving car is a challenging task because of the limited communication time between the vehicle and the RSU. In this paper, we propose a cooperative content placement model for RSUs, in which multiple RSUs can jointly complete the cache and transmission of large files, so that the vehicle users can obtain the target content in the process of high-speed movement. To form cooperative coalitions between RSUs and place as much content as possible, a novel coalition game based distributed cooperative content caching scheme, namely CGD3C, is proposed, in which an RSU cooperative clustering algorithm and a resource balancing based coalition formation algorithm is proposed to merge and split the coalitions, so as to obtain a stable coalition structure. Finally, a cooperative content caching determination algorithm is proposed to determine the content placement with objective of maximizing the current interests. Our simulation results show that our proposed CGD3C can achieve stable and effective content delivery for high-speed moving vehicles, form an optimal RSU coalition structure independently, as well as improve the profit by 15%, the caching resource utilization by 24%, and the request hit rate by 12% on average in comparison with existing schemes.