  Next generation wireless networks are expected to provide much higher data
throughput and reliable connections for a far larger number of wireless service
subscribers and machine-type nodes, which result in increasingly stringent
requirements of spectral efficiency (SE) and energy efficiency (EE). Orthogonal
frequency-division multiplexing with index modulation (OFDM-IM) stands out as a
promising solution to satisfy the SE requirement with a reasonable increase in
system complexity. However, the EE of OFDM-IM is still required to be enhanced.
Moreover, diversity gain is hardly harvested in OFDM-IM systems, which hinders
further reliability enhancement. In this regard, relay assisted OFDM-IM, as a
promising joint paradigm to achieve both high SE and EE, was proposed and has
been studied since last year. The objectives of this article are to summarize
the recent achievements of this joint paradigm, articulate its pros and cons,
and reveal the corresponding challenges and future work.
