BBoF v.s. RFoF in Fiber-Wireless Communication Systems

In this paper, we study the modeling and performance of the downlink of fiber-wireless communication (FWC) systems, where a central unit (CU) is connected through optical links to multiple radio access points (RAPs), which provide wireless coverage to mobile users. For a FWC system that relies on mm-wave wireless signals, a large number of spatially distributed RAPs are usually employed to compensate for the high propagation loss of mm-wave signals. Radio-frequency-over-fiber (RFoF) and baseband-over-fiber (BBoF) are two commonly used techniques for FWC systems. We aim at comparing the performances between RFoF and BBoF systems, such as to identify the operation scenario that one is better than the other, or vice versa. The analysis is performed by modeling the effects of the components on the complete signal path in both RFoF and BBoF systems, such as baseband unit, digital-to-analog converter (DAC), radio-frequency (RF) unit, electrical-optical interfaces, optical fiber, power amplifier, etc. The two systems are compared in terms of total power consumption, noise power, and outage probability. It is demonstrated that the RFoF system outperforms its BBoF counterpart for systems with shorter fiber length (e.g. less than 15.8 km), lower transmission power, and more RAPs, which are all desired properties for future wireless communication systems.