An Optical and mm-Wave Converged, Dual-band, Multi-beam Rotman Lens Antenna Array System Enabling Simplified Designs of B5G/mmW Base Stations for Ultra Dense Wireless Networks

With the exponential demand for additional capacity, ultra-dense wireless networks (UDNs) have become a highly interesting area of study. One of the major challenges in UDN deployment is the complexity and cost of base stations which impacts scalability. This work proposes an integrated system combining optical and millimeter-wave (mmWave) technologies to address these challenges by centralizing processing tasks and simplifying base station. By transmitting signals over fiber from a central location to the base stations, the need for bulky, power-intensive components at each base station is significantly reduced. This architecture opens the door to centralized artificial intelligence-based control of the base station. A dual-band Rotman lens antenna array is integrated into the system to provide flexible, passive beamforming capabilities, supporting multiple frequencies and multiple beams in a compact form, further reducing the overall number of devices required at the base station. The multi-layer Rotman lens antenna achieves a total -3-dB realized gain coverage of ±42° at both 28 GHz and 39 GHz. The maximum realized gain is 12.6 dBi and 12.9 dBi, at 28 GHz and 39 GHz respectively. To demonstrate the capabilities of the proposed optical and mm-Wave converged Rotman-lens enabled simplified base station architectures, a proof-of-concept experiment is performed integrating optical multicarrier generation, optical modulation, fiber transmission, optical-to-electrical conversion and transmission through the presented dual-band, Rotman lens antenna array. The results demonstrate a BER below the hard-decision FEC threshold, EVM meeting IEEE standard requirements, and open eye diagrams, confirming acceptable performance of the proposed architecture for simplified UDN base stations.