Affine Frequency Division Multiplexing with Quadrature Index Modulation

Affine frequency division multiplexing (AFDM) is an emerging multicarrier technique utilizing chirp signals, specifically designed for high-mobility communication scenarios, and it can achieve full diversity. Recently, AFDM with index modulation (AFDM-IM) has been introduced, offering improved bit error rate (BER) performance compared to traditional AFDM systems. In this paper, we propose a novel transmission scheme called AFDM with quadrature index modulation (AFDM-QIM), which enhances the spectral efficiency of AFDM-IM by embedding additional information bits in the subcarrier indices of the AFDM subblock, utilizing both in-phase and quadrature components. A theoretical analysis of the BER performance of AFDM-QIM is provided, along with simulation results. These results demon-strate superior performance of AFDM-QIM over traditional AFDM-IM. This novel approach provides a promising pathway for the development of resilient and efficient communication systems in future high-mobility scenarios.