  The large spectrum available in the millimeter-Wave (mmWave) band has emerged
as a promising solution for meeting the huge capacity requirements of the 5th
generation (5G) wireless networks. However, to fully harness the potential of
mmWave communications, obstacles such as severe path loss, channel sparsity and
hardware complexity should be overcome. In this paper, we introduce a
generalized reconfigurable antenna multiple-input multiple-output (MIMO)
architecture that takes advantage of lens-based reconfigurable antennas. The
considered antennas can support multiple radiation patterns simultaneously by
using a single RF chain. The degrees of freedom provided by the reconfigurable
antennas are used to, first, combat channel sparsity in MIMO mmWave systems.
Further, to suppress high path loss and shadowing at mmWave frequencies, we use
a rate-one space-time block code. Our analysis and simulations show that the
proposed reconfigurable MIMO architecture achieves full-diversity gain by using
linear receivers and without requiring channel state information at the
transmitter. Moreover, simulations show that the proposed architecture
outperforms traditional MIMO transmission schemes in mmWave channel settings.
