Turbo Equalization with Channel Prediction and Iterative Channel Estimation

Abstract

Turbo equalization that cooperates with channel prediction and iterative channel estimation is investigated for mobile broadband communications. Frames of information bits are encoded, interleaved, and mapped to symbols for transmission over time-varying radio channels. The Turbo receiver consists of a maximum a posteriori probability equalizer/demapper and a soft- input soft-output maximum a posteriori probability decoder. With initial channel estimates and sparse pilot insertion across many frames, the receiver predicts the channel of the current frame. The effect of error propagation of channel prediction is mitigated by the de-interleaver that is embedded in the Turbo receiver. The predicted and interpolated channel is refined through the channel estimator that uses the soft estimates of the symbols at each Turbo iteration. Due to the bandlimiting feature of the varying channel, the estimation errors are smoothed by the low-pass filters that follow the channel estimator. Simulation results show that incorporating Turbo equalization with channel prediction and iterative channel estimation can combat fast channel variation and improve reception performance.