W-Band Beamforming Front-End Implementation and Outdoor Trials for Mobile Backhaul and Access

The authors present a W-band Rotman lens (RL) beamformer with WR-10 waveguide interfaces. Radio frequency characteristics, such as phase relationships and insertion losses, including the beamforming capabilities of the RL were simulated and measured to validate the performance of generating four RF beams with ±60° field of view. Subsequently, the RL as beamformer was integrated into a transmitter setup in conjunction with the array antenna, in addition to a receiver setup that was constructed from off-the-shelf components. Both W-band transmitter and receiver were used to demonstrate a wireless link transmission in an outdoor urban - mobile user access or mobile backhauling - deployment scenario; over 85 GHz carrier frequency. The demonstration used a 5G-NR Release-15 conform waveform with 400 MHz of bandwidth and up to 256 quadrature amplitude modulation (QAM). The demonstration trial was conducted including line-of-sight (LOS), obstructed line-of-sight (OLoS), and none-line-of-sight (NLoS) scenarios; and reported a successful 16QAM over 184 meters OLoS link and 16QAM over 116 meters NLoS link. The work provides experimental evidence of the potential for high-frequency bands like the W-band to be utilized in future (6G and beyond) wireless communication networks.