  In contrast to the state-of-the-art technology, it is envisaged that 5G
systems will accommodate a broad range of services and a variety of emerging
applications. In fact, the advent of the Internet of Things (IoT) and its
integration with conventional human-initiated transmissions yields the need for
a fundamental system redesign. Hence, the ideal waveform for the upcoming 5G
radio access technology should cope with several requirements, such as low
computational complexity, good time and frequency localization and
straightforward extension to \emph{multiple-input multiple-output} (MIMO)
systems. In the light of reducing the algorithmic complexity of the spectrally
precoded MIMO OFDM, we provide an in-depth analysis of the use of block
reflectors. The channel capacity formula for MIMO spectrally precoded OFDM is
then derived, and the proposed design techniques are compared to conventional
MIMO OFDM from an information-theoretic perspective.
