  An intelligent reflecting surface (IRS)-assisted millimeter-wave (mmWave)
massive multiple input multiple output (MIMO) system with transmit antenna
selection (TAS) using orthogonal space-time block codes (OSTBC) scheme is
proposed in this paper. This system combines TAS and IRS with hybrid
analog-digital beamforming (HBF) for 60 GHz mmWave communications in order to
exploit the benefits of TAS, OSTBC, analog beamforming (ABF), and transmit
digital precoding techniques. The proposed system, however, benefits from the
transmit diversity gain of OSTBC scheme as well as from the signal-to-noise
ratio (SNR) gains of both the beamformer and the IRS technology. The simulation
results demonstrate that TAS-OSTBC system with zero-forcing precoding technique
outperforms the conventional TAS system with OSTBC scheme. Furthermore, the bit
error rate (BER) performance significantly im-proves as the number of antenna
array elements increases due to providing a beamforming gain. In addition,
increasing the number of reflecting elements further enhances the error
performance. It is also found from the simulation results that the TAS-OSTBC
system with hybrid precoding has better BER performance than that of TAS-OSTBC
with ABF, and IRS-assisted systems significantly outperform the conventional
systems without the IRS technology. This makes the proposed IRS-assisted system
an appealing solution for internet-of-things (IoT) networks.
