Adaptive Interference Suppression for AFDM Channel Estimation Under OFDM Coexistence

As research on affine frequency division multiplexing (AFDM) advances, its coexistence with legacy orthogonal frequency division multiplexing (OFDM) systems remains largely unexplored. Particularly, the integration of AFDM networks into environments dominated by the existing OFDM-based infrastructures poses significant interference challenges for the channel estimation (CE), primarily due to the strong OFDM signaling that affects the reception of AFDM signals. This letter proposes a novel interference suppression technique that exploits the cross-logical-domain projection properties of waveforms. Initially, we demonstrate that the interfering OFDM signal behaves as an additive white Gaussian noise (AWGN) with uniform power distribution in the affine domain. Building upon that, an adaptive iterative windowing scheme is developed, applied over the pilot guard interval, to jointly suppress OFDM interference and detect channel taps prior to CE in the affine domain. Simulation results confirm that the proposed method effectively mitigates interference and significantly improves channel parameter estimation accuracy, while maintaining a low system complexity.