The CommIT hybrid digital-analog (HDA) beamforming testbed is a unique and self developed test system for the hybrid digital-analog approach to massive MIMO. It was developed at the chair within the frame of the A.v.H. Professorship. The testbed can be used to investigate and demonstrate hybrid massive MU-MIMO precoding or other beamforming techniques. It features a scalable structure to support different hybrid architectures and many antennas (up to 64 have been demonstrated, but also more can be connected). It is not constrained to a certain mobile communication protocol or standard and has been demonstrated with e.g. WiFi.

The WiFi version of the testbed is a unique solution based on the hybrid digital-analog beamforming approach to overcome the limitation of commercial WiFi hardware and effectively increase the MU-MIMO gain and to unlock the potential of MU-MIMO in WiFi. We use commercial and of the shelf WiFi hardware in combination with the analog module explained above and novel algorithms for the hybrid approach, leveraging the MU-MIMO precoding of the WiFi system. The implemented control and signal processing software is fully transparent to the WiFi part, i.e., no protocol changes are needed. We demonstrated the increase in MU-MIMO gain using unmodified commercial end-user terminals. The increase in throughput compared to a four element antenna configuration is show in the picture on the right. The hybrid digital-analog beamforming WiFi testbed has been demonstrated during the MobiCom 2020 ACM SIGMOBILE conference. The corresponding short paper and the presentation video are shown below.