Experimental evaluation of distributed ZF beamforming in an indoor multi-cell environment

Multiuser MIMO (MU-MIMO) transmission offers higher channel capacity than SISO transmission in practical system. However, MU-MIMO channel capacity in multi-cell environment is limited by inter-cell interference (ICI). Distributed zero forcing beamforming (DZFBF) is one of candidates to improve MU-MIMO channel capacity by mitigating ICI. To evaluate the performance and feasibility of DZFBF, we have developed a real-time testbed implemented on a FPGA. For this, we also implement a simple weight generation process that uses feedback channel state information from STAs; it is a extension of the weight generation from MU-MIMO systems. Moreover, we demonstrate the real-time transmission performance of our testbed in an actual indoor multi-cell environment. The experimental results indicate that the effectiveness of DZFBF is twice as high as that of MU-MIMO transmission with TDMA.