On Offloading Fog Radio Access Networks Fronthaul Using Device Caching and Cooperation

Abstract

This paper studies the problem of offloading the fronthaul of Fog Radio Access Networks (F-RANs) with smart user equipments (denoted by F-UEs) that can cache files and cooperate with each other to retrieve their requested files. This cooperation between the F-UE devices will reduce the load on the fronthaul of the central baseband processing unit (BBU), thus increasing the overall capacity of the network. By smartly employing network coding (NC), this paper aims to minimize the number of transmissions required from the BBU given a realistic half-duplex transmission scenario. In this setting, F-UE devices can only send or receive at a time, and thus must receive their requested files in maximum two time-slots in order to achieve high quality of experience (QoE). The above problem is first formulated over an NC graph. Being NP-hard, two heuristic algorithms are proposed to solve the problem in real-time. Simulation results show that these proposed heuristics perform closely to the optimal solution. They also demonstrate the significant fronthaul offloading gains achieved by our proposed algorithms.