Network planning of uplink all-optical passive FSO/OF C-RAN fronthaul

Though the cloud radio access network (C-RAN) architecture is promising to allow for the necessary densification of radio networks in future systems, their utility relies on the availability of high-bandwidth reliable fronthaul links. In this paper, we propose a new all-optical fronthaul architecture in which user signals are forwarded over radio-over-free-space-optics (RoFSO) fronthaul that is passively coupled to an optical fiber (OF) for transport to a central office. We develop tools to plan such a network to optimize the outage probability while considering the coverage area, the density of the radio units (RUs), and the signal gain at the RUs. Each of these parameters can be designed to maintain an upperbound of the outage probability. Analytical expressions of the outage probability of the fronthaul network as well as the optimum RU gain are obtained. For a realistic design, clipping noise, atmospheric scintillation, and the effect of different weather conditions are considered for the RoFSO links, while nonlinear interference is modeled in the OF link. Given a required outage probability and density of RUs, the tools developed here can give the coverage area as well as optimum values for transmitted optical power and gain to balance the impact of all impairments.