  Spatial modulation (SM) transmits additional information bits by the
selection of antennas. Generalized spatial modulation (GSM), as an advanced
type of SM, can be divided into diversity and multiplexing (MUX) schemes
according to the symbols carried on the selected antennas are identical or
different. Recently, reconfigurable intelligent surface (RIS) assisted SM
exhibits better reception performance compared to conventional SM. To overcome
the limitations of SM, this paper combines GSM with RIS and proposes the
RIS-aided receive generalized spatial modulation (RIS-RGSM) scheme. The
RIS-RGSM diversity scheme is realized via a simple improvement based on the
state-of-the-art scheme. To further increase the transmission rate, a novel
RIS-RGSM MUX scheme is proposed, where the reflection phase shifts and on/off
states of RIS elements are configured to achieve bit mapping. The theoretical
bit error rate (BER) of the proposed scheme is derived and agrees well with the
simulation results. Numerical simulations show that the RIS-RGSM MUX scheme has
better BER performance than the diversity scheme. The proposed scheme can
significantly increase the transmission rate and maintain good performance
compared to the existing scheme under a limited number of antennas.
