  The idea of media-based modulation (MBM) is to embed information in the
channel states via intentional perturbations of the transmission media. This
article covers a broad range of topics regarding MBM, expanding on its benefits
and reviewing relevant challenges, alluding to potential future research
directions. The article starts by arguing how MBM differs from a source-based
modulation; we highlight the key shortcomings in a legacy multiple-input
multiple-output (MIMO) system that MBM sets out to address, including the issue
of deep fades and MIMO diversity-multiplexing trade-off. The article further
explains how MBM works in harmony with other index modulations and improves
upon them by providing similar advantages with a more compact transmitter.
Numerical results (simulation and analytical) are provided to support the
claims on the discussed benefits. The highlights of numerical results include:
1) outage comparison with legacy MIMO systems; 2) comparisons with other
state-of-the-art modulation schemes such as generalized spatial modulation; and
3) performance example of sending 32 bits of information in a single
transmission with an excellent symbol error rate of $\mathsf{SER} \simeq
10^{-5}$ at \say{energy per bit to noise power spectral density ratio} of
$\mathsf{E_b/N_0} \simeq -3.5$ dB. The article continues with methods to
address the issues of receiver training and decoding for large constellation
sets. A number of other research questions, such as pulse shaping to limit
spectral growth due to the time-varying nature of MBM and the effect of forward
error correcting codes on MBM diversity order are discussed. Finally, an RF
transceiver structure is presented to generate independent propagation paths
for embedding information. Fabrication and testing of the transceiver structure
show close agreement between simulation and measurement.
