We present a novel beamforming technique

for multi-user frequency-selective indoor channels called

interference-nulling time-reversal (INTR). The beamformer is

implemented with a pre-filter designed to minimize the interuser

interference present in conventional time-reversal (TR).

Moreover, our technique relies on a large number of antennas at

the transmitter to mitigate inter-symbol interference, enabling

low computational complexity receivers. We demonstrate that

INTR outperforms previous TR techniques with respect to

average bit error rate per user and achievable sum rate. Thus,

INTR can be used for space division multiple access in no-Iine-ofsight

mm-wave massive MIMO, providing remarkable diversity

and multiplexing gains.