Cross-Layer Cloud Offloading With Quality of Service Guarantees in Fog-RANs

Fog radio access networks (F-RANs) have recently been postulated as an innovative solution to improve the fronthaul capacities of cloud base stations (CBSs). This architecture extends the CBS service by involving enhanced remote radio heads (eRRHs), which can pre-store and transmit popular files at the network edge (i.e., close to the end users). This is referred to as caching, and it allows the offloading of CBS resources, e.g., time and frequency. Recent works have been proposed to use rate-aware network coding in order to exploit the previously downloaded popular files at the users’ devices. As such, the CBS offloading is maximized. However, the users’ achieved Quality of Service (QoS), and the standard F-RANs physical-layer resource optimization have not received any attention to date. This paper proposes use of an innovative cross-layer network coding (CLNC) to address the above-mentioned issues. The proposed CLNC scheme is not only aware of different users’ rates but also controls the rates by jointly optimizing coding combinations, users-eRRHs/power zones (PZs) assignments, and transmission power in the PZs. Using a graph theoretical representation, we formulate the joint cross-layer CBS offloading and QoS guarantee problem and show its NP-hardness. Joint and iterative heuristic approaches are then developed to solve this problem using greedy vertex search and coloring techniques. The proposed approaches are finally validated and tested against the existing algorithms in the literature.