Index modulation (IM) techniques are emerging
as promising approaches to improve spectral efficiency and
reliability for 5G/future wireless networks. This paper pro vides an overview of key IM schemes including spatial modula tion, orthogonal frequency division multiplexing with index
modulation (OFDM-IM), and enhanced variants like SIM OFDM. The spectral efficiency gains of these techniques are
quantified mathematically. Spatial modulation uses antenna
indices to convey additional information bits, while OFDM-IM
utilizes subcarrier indices. SIM-OFDM further activates sub carriers selectively based on incoming bits. Experiments demonstrate spectral efficiency improvements over classical
OFDM.
