To improve the spectral efficiency of multicarrier modulation, a multicarrier modulation scheme, called generalized frequency division multiplexing with real and imaginary indices modulation (GFDM-RIIM) is proposed. In this scheme, the subcarrier index is divided into real part index and imaginary part index, and this allows the system to carry more information. The GFDM-RIIM system model is presented and the complexity, spectral efficiency and the bit error rate performance under Rayleigh multipath fading channels are analyzed. It is shown that the GFDM-RIIM achieves a higher spectral efficiency and better reliability than the existing GFDM, generalized frequency division multiplexing with index modulation, orthogonal frequency division multiplex, filter bank based multicarrier schemes.