An Ultra-Reliable MMW/FSO A-RoF System Based on Coordinated Mapping and Combining Technique for 5G and Beyond Mobile Fronthaul

We propose and experimentally demonstrate, for the first time, a system which integrates millimeter-wave (MMW) and free-space-optics (FSO) analog radio-over-fiber (A-RoF) channels, and provides enhanced reliability in 5G and beyond mobile fronthaul (MFH) links. The integrated system utilizes a novel coordinated mapping and combining (CMC) technique that senses the signal quality in each data block and apportions the load accordingly. Furthermore, the technique takes advantage of the abundant bandwidth in both MMW and FSO links and is compatible with orthogonal frequency division multiplexing (OFDM). In the CMC design, the data blocks at the transmitter side are interleaved and repeated in both the frequency domain and the time domain, and then the duplicated blocks are combined with adaptive weight coefficients at the receiver side. We demonstrate experimentally that the proposed CMC technique improves power margins and enhances the robustness of the adaptive diversity combining technique (ADCT)-based FSO/MMW links by mitigating system impairments caused by frequency/time burst interference and power fading attributable to adverse weather conditions. In experiments, compared with the ADCT-based system, we find a 9 dB gain in received optical power tolerance and a 5.8 dB lower EVM floor under a deliberately injected 20-MHz LTE frequency interference burst.