Constant Envelope Orthogonal Frequency Division Multiplexing With Index Modulation

Phase modulation has played a crucial role in rendering constant envelope orthogonal frequency division multiplexing (CE-OFDM) an appealing waveform, characterized by its 0 dB peak-to-average power ratio (PAPR). However, an inherent tradeoff between bit error rate (BER) performance and bandwidth poses a considerable hurdle that is detrimental to the wideranging adoption of CE-OFDM. To overcome this challenge, we intrinsically integrate index modulation (IM) with CE-OFDM for the purpose of realizing the full potential of frequency diversity gains, yielding improved BER performance without occupying too many bandwidth resources. We have also develop a pair of detectors for the proposed CE-OFDM-IM scheme, including the optimal but high-complexity maximum likelihood (ML) detector, the low-complexity phase detector, and the novel reduced-space ML receiver, offering flexible designs for different optimization goals. Moreover, the theoretical performance of the proposed CE-OFDM-IM scheme is mathematically quantified through derivations. Our simulation results confirm the precision of the theoretical analysis, and demonstrate that the proposed framework is capable of providing a favourable performance gain over the original CE-OFDM scheme, especially for channels with substantial multi-path components.