Integration of wireless and optical technologies to meet the requirements of 5G networks and beyond

The Centralized Radio Access Network (C-RAN) architecture is necessary to achieve the target goals that have been set for 5G. However, as the number of radio signals to be transported between the Centralized Base Station (CBS) and the Remote Antenna Units (RAUs) grows large, the utilization of contemporary fronthaul technologies (such as CPRI) becomes more difficult. The reason for this is that these Digital Radio-over- Fibre (RoF) solutions were originally designed to be transparent to the transported radio signal, introducing a negligible distortion at the cost of expanding the bandwidth notably and increasing the processing delay. As the assumption of an ideal fronthaul will not be realistic any more for future C-RANs, a novel design paradigm is needed in which the impairments introduced by both fibre fronthaul and wireless air-interface are jointly taken into account. In this contribution, we present our vision about the advantages of using an all-analog fronthaul, identifying potential challenges and proposing possible solutions to address each of them. We claim that the use of low-cost analog components in the RAUs will not only reduce the End-to-End (E2E) latency of the mobile network, but will also enable an ultra-dense deployment of small cells taking advantage of the Passive Optical Network (PON) infrastructure that is already available today in most urban centres.Grant numbers : This work has received funding from the Spanish Government under Project TEC2014-59255-C3-1-R (ELISA) and the Catalan Government under Grant 2014SGR1567