Experimental evaluation of digital beamforming for 5G multi-site massive MIMO

In order to tackle rapidly increasing traffic, Massive MIMO using beamforming (BF) is promising technique for fifth-generation (5G) mobile communication systems. Authors have recently proposed the joint processing of digital fixed BF and channel state information (CSI)-based precoding (Digital FBCP) that is suitable for low-SHF-band Massive MIMO. It has been also clarified that Digital FBCP is efficient in not-only single-site but also multi-site environment by introducing extended precoding technique. Although the previous works evaluate only in computer simulations, this paper aims to evaluate real-field performances by using 5G low-SHF-band massive MIMO prototype. First we measure low-SHF-band (5.2 GHz-band) CSI data in outdoor experiment, and then, this paper optimizes beam parameter in computer simulations exploiting the measured data. Finally, we show the throughput performance of Digital FBCP in multi-site environments.