A Single-Pilot-Aided Channel Estimation Scheme Based on Interference Position Indices for AFDM in Delay-Doppler Channels

The newly introduced affine frequency division multiplexing (AFDM) modulation exhibits the remarkable capacity within highly mobile scenarios. Particularly, AFDM modulation is capable of attaining full diversity and offering a complete sparse representation of the channel. Thereby, it is possible to accomplish accurate channel estimation (CE) by utilizing a single pilot symbol. Nevertheless, guard intervals (GI) are required to be employed by the present AFDM channel estimation strategies, with the spectral efficiency (SE) being unavoidably diminished. In this letter, a CE scheme without the GI is utilized. In order to alleviate the pilot-data interference resulting from the lack of the GI, we present a method of determining the position indices of the elements that introduce interference from the pilot and data in the received signals. Then, interference cancellation, data detection and channel estimation are iteratively conducted. Simulation results show that the method achieves good bit error rate performance, while improving the SE.