  The concept of reconfigurable intelligent surface (RIS)-assisted
transmission, where phases of reflected signals are adjusted in an effective
arrangement, has been recently put forward as a promising solution for 6G and
beyond networks. Considering this and the undeniable potential of index
modulation (IM) techniques, an RIS-based space shift keying (SSK) scheme is
proposed in this letter to maintain all inherent advantages of both RISs and
SSK. Specifically, a mathematical framework is presented by using a maximum
likelihood (ML) detector for the calculation of the average bit error rate
(ABER). Extensive computer simulation results are provided to assess the
potential of the proposed RIS-based SSK system and to verify the theoretical
derivations. The obtained results indicate that the proposed scheme enables
highly reliable transmission with unconventionally high energy efficiency,
however with the added cost of increased receiver complexity.
