Doubly Differential OFDM Employing an Intercarrier Interference Self-Canceller for Underwater Acoustic Communications

This paper proposes doubly differential orthogonal frequency division multiplexing (OFDM) for underwater acoustic communications (UWACs) in the presence of large Doppler shifts. UWAC channels suffer from severe time and frequency selectivities, i.e., double selectivity. OFDM is a good solution for frequency selectivity, and differential encoding/differential detection (DE/DD) is a good solution for time selectivity. DE/DD can cope with time selectivity without insertion of pilot-symbol. However, OFDM suffers from intercarrier interference (ICI) due to its narrow subcarrier spacing. Although an intercarrier interference self-canceller (ICISC) can cancel ICI for differential OFDM, DE/DD cannot cope with severe time-selective channels. In order to solve these issues, this paper proposes doubly differential OFDM employing the ICISC for severe doubly-selective channels. Finally, computer simulation results confirm that the proposed doubly differential OFDM has excellent performance on UWAC channels.