Implementation of HetNet architectures based on FSO, VLC, RoF, and photonics-based RF generation toward 6G applications

This paper presents two distinct network architectures designed to address the demands of 5G/6G applications. The first architecture is an analog radio-over-fiber (RoF) optical fronthaul operating in the V-band at 60 GHz, integrated within a wavelength-division multiplexing passive optical network (WDM-PON). This setup employs photonic techniques for RF signal generation, specifically using carrier-suppressed double sideband (CS-DSB) modulation via Mach–Zehnder modulators (MZMs), enabling efficient frequency multiplication and signal transport. Experimental results demonstrate its ability to achieve a data rate of approximately 11.8 Gbit/s, meeting the requirements for 5G/6G cell densification. The second architecture is a heterogeneous network (HetNet) that combines fiber-wireless (FiWi), free space optics (FSO), and visible light communication (VLC) technologies in a unified network configuration designed for indoor 6G solutions. This HetNet architecture was tested at 39 GHz and features a 20 km optical fiber midhaul, an FSO fronthaul, and a dual VLC/RF access network. The setup was evaluated based on the root mean square error vector magnitude ( ${{\rm EVM}_{{\rm RMS}}}$ ) requirements, with results indicating satisfactory coexistence of the employed technologies, achieving a total data throughput of 1.5 Gbit/s.