Channel Capacity of OFDM with Index Modulation

I am trying to figure out the channel capacity of OFDM with index modulation (OFDM-IM). One of the article reports that the conditional channel capacity of OFDM-IM is $$\mathcal{C}_{\mathrm{OFDM-IM}}(\gamma) = \frac{1}{L}\left[I(\boldsymbol{x}_s;\boldsymbol{y}\vert \boldsymbol{x}_c)+I(\boldsymbol{x}_c;\boldsymbol{y})\right]$$, where $$\gamma$$ is the SNR, $$L$$ is the number of subcarriers available for modulation in one group, $$I(\boldsymbol{x}_s;\boldsymbol{y}\vert \boldsymbol{x}_c)$$ provides constellation domain information, $$I(\boldsymbol{x}_c;\boldsymbol{y})$$ is the index domain information and $$\boldsymbol{y}$$ is the vector of received symbol. I was wondering whether this relation is only valid when we expect a complex-valued signal after IFFT? Secondly, how would this relation change if we need a real-valued signal after IFFT, i.e., when Hermitian symmetry is enforced in the frequency domain prior to IFFT?