Toward Unobstructed Millimeter-Wave 6G: Coordinated Multipoint Transmission Over a Fiber Wireless Distributed Antenna System

Millimeter wave (mmWave) frequencies offer broad channel-bandwidths in 6 G Radio Access Networks (RANs), but can be severely limited by channel outages and blockage phenomena in realistic non-line of sight field-environments. This work experimentally presents the first, outdoor 3× 1 Fiber Wireless (FiWi) mmWave Distributed Antenna System (DAS) across 7km fiber-distances and 30m wireless radio links, Software Defined Controlled (SDN) Coordinated Multipoint (CoMP) scheduled transmissions from three rooftop antennas to a mobile UE. The proposed system relies on wavelength-tunable transmissions through an all-passive, energy-efficient 32× 32 AWGR and an algorithmic workflow that continuously monitors the FiWi link status, allowing for a scalable solution with even higher number of antennas and interfaces. The system is thoroughly evaluated in the physical layer, exhibiting up to 4.5Gb/s data-rate at a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$25^{o}$</tex-math></inline-formula> degree beam-width and latency down to less than 0.2ms. Continuous, SDN-controlled CoMP transmission is initially presented in pre-defined time-slots that alternate the three FiWi paths every 1s with high 14.4dB isolation and 25 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s switching time. Unobstructed connectivity scenario is also experimentally presented, where an intentional mmWave blockage and link outage triggers a zero-touch re-routing and scheduling of upcoming traffic to the UE via an alternate path, selected in a round robbin manner. Finally, real-time streaming services and computation offloading of typical 6G applications at a nearby MEC server confirm the capability of the proposed system to provide high-availability services, shaping a promising roadmap for self-organizing 6G mmWave networks.