Channel polarization and application of OFDM underwater acoustic communication

Existing research has referenced polar code construction methods in wireless channels to estimate the instantaneous reliability for underwater acoustic (UWA) polarized sub-channels. However, it overlooks potential mismatches between the instantaneous codebook and the actual channel state caused by complex time-varying characteristics of UWA channel, and lacks sufficient study on the evolution of sub-channel reliability. This paper extends the foundational channel polarization theory to propose a new framework for parallel UWA channel polarization based on Orthogonal Frequency Division Multiplexing (OFDM). By integrating the time–frequency statistical characteristics of UWA channels, the reliability theoretical model of polarized channels was established. And the intrinsic relationship between its evolution and channel parameters as well as system performance was deeply analyzed. Moreover, through simulation and lake trials, this paper investigates the time–frequency variation of polarized sub-channel reliability under incomplete channel polarization with finite code length. Additionally, it analyzes the impact of UWA channel parameters, such as Doppler shift and time-variation, on channel polarization distribution and polar-coded OFDM system performance. This paper provides a reference for subsequent practical polar coded OFDM communication, and streamlines the code construction process by avoiding the repeated assessments of polarized sub-channel’s reliability.