PlaceRAN: Optimal Placement of Virtualized Network Functions in the Next-generation Radio Access Networks

The fifth-generation mobile evolution introduces Next-Generation Radio Access Networks (NG-RAN) based on the protocol stack disaggregation to enable flexibility to support users' demand for ultra-low latency and high-bandwidth applications. For example, Open RAN solutions focus on an NG-RAN with general-purpose vendor-neutral hardware, software-defined technologies, and interoperability, splitting the protocol stack into the eight options combined into three network units, i.e., central, Distributed, and Radio. These network units and the protocols disaggregated are managed as radio functions. These functions' placement is challenging since the best decision is based on the RAN protocol stack split, routing paths of transport networks with restricted bandwidth and latency requirements, different topologies and link capabilities, asymmetric computational resources, etc. Therefore, this article proposes the first exact model for the placement optimization of radio functions for vNG-RAN planning, named PlaceRAN. The main objective is to minimize the computing resources and maximize the aggregation of radio functions. The PlaceRAN evaluation considered two real network topologies based on 5G-crosshaul and Passion European projects. The PlaceRAN performance reaches up to 80\% aggregation of radio functions centralized.