  We present Affine Frequency Division Multiplexing (AFDM), a new chirp-based
multicarrier transceiver scheme for high mobility communications in
next-generation wireless systems. AFDM is based on discrete affine Fourier
transform (DAFT), a generalization of discrete Fourier transform characterized
with two parameters that can be adapted to better cope with doubly dispersive
channels. Based on the derived input-output relation, the DAFT parameters
underlying AFDM are set in such a way to avoid that time domain channel paths
with distinct delays or Doppler frequency shifts overlap in the DAFT domain.
The resulting DAFT domain impulse response thus conveys a full delay-Doppler
representation of the channel. We show that AFDM can achieve the full diversity
of linear time-varying (LTV) channels. Our analytical results are validated
through numerical simulations, which evince that AFDM outperforms
state-of-the-art multicarrier schemes in terms of bit error rate (BER) in
doubly dispersive channels.
