Cross-Layer Traffic Engineering for Software-Defined Radio Access Networks

We consider the problem of traffic engineering (TE) in a software-defined radio access network (SD-RAN) consisting of backhaul and radio access parts. The role of TE is to route traffic from sources to their corresponding destinations in the network based on its knowledge of network topology and link capacities. Unlike wired networks, where links have fixed capacities, the capacity of a wireless link in a radio access network depends on the amount of resource (e.g., frequency, time, etc.) assigned to it by wireless link scheduler. Therefore, TE for SD-RAN also involves optimization of link/user scheduling. We propose a cross-layer solution by decoupling the SD-RAN TE problem into a wired network TE problem and a user scheduling problem using alternating direction method of multipliers (ADMM). The ADMM iterations are guaranteed to converge if the objective function of the SD-RAN TE problem is convex. The simulation results show that our proposed online implementation closely follows the optimal solution in a dynamic setting where individual flows independently join/leave the network.