Turbo Equalization for Time-Varying Underwater Acoustic Channels with Imperfect Channel State Information

Abstract

Turbo equalization is commonly employed to compensate for multipath propagation in underwater acoustic (UWA) communication. However, the performance of turbo equalization degrades due to the imperfect channel state information (CSI) and time-varying channels. Herein, we first introduce a new derivation for turbo equalization based on the joint Gaussian criterion. On the basis of this derivation, a novel turbo equalization algorithm for time-varying UWA channels with imperfect CSI is proposed. The algorithm combines the imperfect CSI with the temporal coherence characteristics of UWA channels, which are modeled as a first-order autoregressive (AR(1)) process, to achieve a more accurate channel a posteriori distribution. Afterward, the refined distribution is incorporated into the design of the turbo equalizer, which can effectively reduce intersymbol interference and the Doppler effect. Simulation results show that the proposed algorithm has a better bit error rate performance than other turbo equalization algorithms with channel estimation error compensation or the AR(1) process for any iteration in fast time-varying scenarios.

Keywords

Imperfect channel state information / First-order autoregressive process / Turbo equalization / Time-varying channels / Underwater acoustics communication

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Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature