PAPR Reduction with Pre-chirp Selection for Affine Frequency Division Multiplexing

Affine frequency division multiplexing (AFDM) is a promising new multicarrier technique for high-mobility communications based on discrete affine Fourier transform (DAFT). By properly tuning the pre-chirp parameter and the post-chirp parameter in the DAFT, the effective channel in the DAFT domain can completely circumvent path overlap, thereby constituting a full representation of delay-Doppler profile. However, AFDM has a crucial problem of high peak-to-average power ratio (PAPR), stemming from randomness of modulated symbols. In this letter, a novel algorithm named grouped pre-chirp selection (GPS) is proposed to reduce PAPR by strategically varying the pre-chirp parameter across subcarrier groups. Initially, it is established that key AFDM properties are maintained when implementing GPS. Next, we proceed to detail the operational procedures of the GPS algorithm, elucidating its principle for PAPR reduction and emphasizing its computational efficiency advantages. Finally, simulation results employing the complementary cumulative distribution function (CCDF) validate the effectiveness of the proposed GPS in reducing PAPR.