Evaluation of massive MIMO systems using time-reversal beamforming technique

In this paper, we investigate the performance of a massive MIMO system using the time-reversal beamforming technique. The massive MIMO channels are simulated with ray-tracing at 3.5 GHz with a 200 MHz-bandwidth. We use a 64-element uniform cylindrical array as base station (BS) and we equip two users with single omnidirectional antennas. By applying convenient weights to the emitted signals, we expect to improve the useful signal level by both classic beamforming and time-focusing gains, while decreasing the inter-user interferences (IUI). The performance of the system is evaluated by the signal-to-noise (SNR) and signal-to-interference-plus-noise ratio (SINR) in a 10-path channel with line-of-sight (LOS). We compare the performance with the case where the BS is equipped with an omnidirectional antenna and without pre-processing. In this situation, the results show an SNR improvement up to 25 dB yet the output SINR is limited by the inter-symbol interferences (ISI), especially caused by the ground reflection.