Space-Time-Frequency Index Modulation in Optical Wireless Communications

To address the issue of insufficient transmission rates in existing optical wireless communication systems relying on single-resource-dimensional index modulation, this paper introduces joint index modulation across multiple resource dimensions. We propose a Space-Time-Frequency Index Shift Keying (STFISK) scheme for optical wireless communications and derive the upper bound of its average bit error rate (BER) under the maximum likelihood (ML) criterion. Results demonstrate that, compared to conventional single-domain index modulation systems, the proposed scheme significantly improves both transmission rate and BER performance while incurring only minimal resource utilization loss.