5G Xhaul and Service Convergence: Transmission, Switching and Automation Enabling Technologies

The article provides a review of the Xhaul network in terms of architecture, transmission, switching, and service provisioning automation, with the objective to illustrate the state of the art and indicate the open issues to be addressed. Xhaul is the new transport network segment that covers the first 15-20 km from the access site, replacing today point-to-point fronthaul connections. Due to the high level of capillarity of deployed equipment in this network segment, a simple downsize of the technology used in metro and aggregation networks cannot achieve sufficient cost effectiveness: cost reduction, both in opex and capex, must indeed not compromise the demanding requirements of low latency and high bandwidth. Enabling service convergence is the key feature of Xhaul. The considered network scenario starts from an initial phase, where the Xhaul infrastructure is designed to carry only mobile fronthaul and backhaul traffic, evolving to support enterprises services, as well as vertical services. Such a convergent infrastructure has to support any kind of 5G service, including massive Machine Type Communication (mMTC), extreme Mobile Broad-Band (eMBB), and Ultra-Reliable Low Latency Communication (URLLC). The most important challenges and significant features are illustrated through relevant examples and experiments.