Optical layer routing influence on software-defined C-RAN survivability

Cloud radio access network (C-RAN) architecture based on heterogeneous radio resources and centralized processing holds promise for satisfying the diverse requirements of fifth-generation mobile applications. In order to provide fronthaul/backhaul connectivity to the radio resources, not only does a dynamic software-defined networking (SDN) optical transport (X-haul) solution resolve the capacity scaling bottlenecks, it can also lead to statistical multiplexing gains and power efficiency in the system. Infrastructure programmability due to SDN, however, can result in network reliability concerns due to the inherent cyber-physical interdependency between the physical fiber and the higher-layer (IP) control networks. In this paper, we study the SDN C-RAN robustness to node failures, considering the interplay of wireless, optical, and control domains, and examine the effectiveness of two optical-layer routing mechanisms, i.e., static load balancing and dynamic routing, for survivable system operation. Our Monte Carlo analysis points to the marginal advantage of load balancing, irrespective of connection distribution in the control plane. However, optical X-haul programmability provides for robust C-RAN operation with essentially no sensitivity to critical network elements and negligible penalty in terms of fronthaul segment latency.