Transmission through large intelligent surfaces (LIS), which modify the
phases of incident waves in a deliberate manner to enhance the signal quality
at the receiver, has been recently put forward as a promising candidate for
future wireless communication systems and standards. In this paper, we bring
the concept of LIS-assisted communications to the realm of index modulation
(IM) by proposing LIS-space shift keying (LIS-SSK) and LIS-spatial modulation
(LIS-SM) schemes. These two schemes are realized through not only intelligent
reflection of the incoming electromagnetic waves to improve the signal quality
at the receiver but also utilization of the IM principle for the indices of
multiple receive antennas in a clever way to improve the spectral efficiency.
Maximum energy-based suboptimal (greedy) and exhaustive search-based optimal
(maximum likelihood) detectors of the LIS-SSK/SM schemes are formulated and a
unified framework is presented for the derivation of the theoretical average
bit error probability of the proposed schemes using both detectors. Extensive
computer simulation results are provided to assess the potential of
LIS-assisted IM schemes as well as to verify our theoretical derivations and
remarks. Our findings also reveal that LIS-based IM, which enables
ultra-reliable transmission with high spectral efficiency, can become a
potential candidate for future wireless communication systems in the context of
beyond massive multiple-input multiple-output (MIMO) solutions.