  The cost of radio frequency (RF) chains is the biggest drawback of massive
MIMO millimeter wave networks. By employing spatial modulation (SM), it is
possible to implement lower number of RF chains than transmit antennas but
still achieve high spectral efficiency. In this work, we propose a system model
of the SM scheme together with hybrid beamforming at the transmitter and
digital combining at the receiver. In the proposed model, spatially-modulated
bits are mapped onto indices of antenna arrays. It is shown that the proposed
model achieves approximately 5dB gain over classical multi-user SM scheme with
only 8 transmit antennas at each antenna array. This gain can be improved
further by increasing the number of transmit antennas at each array without
increasing the number of RF chains.
