  Indexed modulation (IM) is an evolving technique that has become popular due
to its ability of parallel data communication over distinct combinations of
transmission entities. In this article, we first provide a comprehensive survey
of IM-enabled multiple access (MA) techniques, emphasizing the shortcomings of
existing non-indexed MA schemes. Theoretical comparisons are presented to show
how the notion of indexing eliminates the limitations of non-indexed solutions.
We also discuss the benefits that the utilization of a reconfigurable
intelligent surface (RIS) can offer when deployed as an indexing entity. In
particular, we propose an RIS-indexed multiple access (RIMA) transmission
scheme that utilizes dynamic phase tuning to embed multi-user information over
a single carrier. The performance of the proposed RIMA is assessed in light of
simulation results that confirm its performance gains. The article further
includes a list of relevant open technical issues and research directions.
