Edge Cooperation Based Coded Caching in Fog Radio Access Networks

In this paper, we investigate edge cooperation based coded caching in fog radio access networks (F-RANs). Initially, we propose a cooperative coded caching scheme which utilizes cooperation between fog access points (F-APs) to facilitate efficient multicasting. In this scheme, to achieve a higher caching gain, we design the tiered placement strategy; to reduce the multicasting gain losses as well as the delay and energy costs of multicasting, we propose the differential encoding based delivery strategy. Moreover, in order to better fully utilize the edge-computing capabilities of F-RANs, neighboring F-APs are clustered to enable multiple F-APs to utilize the mixed caching scheme to collaboratively serve one user, thereby leveraging the potential gains in the physical layer cooperation. The inter-cluster cooperative coded caching scheme and the inner-cluster mixed caching scheme compose the comprehensive caching scheme that is analyzed and optimized in terms of delay and energy efficiency (EE). Simulation results show that our proposed cooperative coded caching scheme can provide up to 46% savings in the transmission cost compared to the conventional group-based coded caching scheme, and the comprehensive caching scheme can achieve significant flexibility in delay-sensitive and EE-sensitive scenarios.