Analog vs. next-generation digital fronthaul: How to minimize optical bandwidth utilization

In this paper we investigate two promising approaches to reduce the optical bandwidth utilization in the mobile fronthaul of next-generation cloud radio access networks. We analyze and compare the performance of an analog radio-over-fiber and a new digital fronthaul in a chromatic dispersion-limited scenario. The former uses several analog channels, generated by up- and down-converting of baseband signals, and the latter utilizes simple OOK NRZ for the transmission to the remote radio head. Both principles are applied to a custom millimeter-wave system, consisting of several analog channels with baseband bandwidths as expected for 5G. The performance of both concepts at transmission rates of up to 100 Gb/s and 100 km of fiber is evaluated. We will show that both approaches are suitable for transmission distances typical for fronthaul and discuss their advantages and disadvantages. Furthermore, an optimized bandwidth concept for the analog radio-over-fiber system is presented, which enables transmission distances on the scale of metro networks.