Demonstration of a hybrid optical fiber–wireless 5G fronthaul coexisting with end-to-end 4G networks

The plethora of services envisaged to support 5G use-cases requires the development of a radio access network (RAN) infrastructure with the capability to integrate a variety of user-demanded mobile traffic characteristics. It is therefore interesting to study a 5G deployment scenario showcasing heterogeneous transmission. In order to address this challenge, in this paper, we propose and experimentally assess a coarse-wavelength-division-multiplexing-compatible optical access network for joint provisioning of 4G/5G RAN services, supporting the coexistence of both digital and analog radio-over-fiber (ARoF) fronthauling. Resorting to an integrated testbed, we demonstrate the transport of 100 MHz 5G downlink using low-latency and bandwidth-efficient ARoF over 8 km fiber, seamlessly coexisting on the same fronthaul infrastructure with a legacy full-fledged 4G long-term evolution (LTE) network supported by Ethernet-based digital RoF with different functional splits. In addition, we experimentally demonstrate the successful operation of the 4G/5G system in a hybrid fiber–wireless scenario including a free-space optics fronthaul extension with 55 m. The proposed heterogeneous RAN architecture is demonstrated to provide a flexible and robust integration path for novel 5G technologies, enabling their coexistence with currently deployed 4G LTE systems over a shared fronthaul infrastructure.