Isolation-Aware 5G RAN Slice Mapping over WDM Metro-Aggregation Networks

To accommodate the heterogeneous requirements of emerging 5G services, 5G Radio Access Network (RAN) will support the rising paradigm of network slicing, where a single physical RAN infrastructure is divided into multiple logical networks characterized by diverse requirements in terms of performance, cost, latency, and security, etc. The optimality of RAN slicing depends on various factors, such as slice requirements, resource availability and adopted network architecture. In 4G, RAN architecture evolved from a distributed architecture towards a 2-layer architecture that separates remote radio heads (RRHs) from baseband processing units (BBUs). However, this architecture has soon shown scalability limitations. To address this problem, the concept of flexible 5G functional split has been proposed, where RAN functions are distributed on a 3-layer architecture featuring a radio unit (RU), a distributed unit (DU), and a central unit (CU). Besides RAN architecture, isolation among different slices, which is necessary for slicing security, has a significant influence on the RAN slicing. In this work, we consider the isolation-aware RAN slice mapping problem considering advanced functional splits and a 3-layer RAN architecture. We propose a dual-objective heuristic algorithm for RAN slice mapping over a physical infrastructure represented by a wavelength division multiplexing (WDM) metro-aggregation networks. The proposed heuristic targets the minimization of 1) the number of active COs (i.e, hosting DUs and/or CUs) and 2) the number of established wavelength channels under constraints of network capacity and latency requirements. As our algorithm is also designed to map the RAN slices with least amount of physical resources for a given level of isolation, we also investigate the impact of slice isolation on resource utilization. Results show how higher isolation results in higher network cost.