Cost-Effective and Power-Efficient Beamforming Remote Antenna Units for Millimeterwave Distributed Antenna Systems

To support the most demanding new applications, beyond5G systems will more than ever rely on multi-antenna deployments and mm-wave spectrum. Unfortunately, due to its propagation properties, ultra-reliable high-data-rate mm-wave coverage seems elusive. Distributed antenna systems based on mm-wave-over-fiber constitute a strong candidate technology to unlock reliable mm-wave coverage, although the concept critically depends for a large part on the availability of cost-effective and power-efficient remote antenna units (RAUs). This contribution identifies two promising implementations for cost-effective and power-efficient beamforming at RAU-level, being a wideband Butler-matrix-based solution and a leaky-wave antenna (LWA), and validates them by means of system-level measurements. While the LWA-based RAU results in the lowest complexity with continuous beamsteering control, accurate control of the signal’s carrier frequency is required, which is unacceptable for many applications. Notwithstanding its slightly higher complexity, the Butler-matrix-based RAU is widely applicable and allows reuse of the same frequency spectrum for multiple sectors.