PN sequence based Doppler and channel estimation for underwater acoustic OFDM communication

Aiming at the requirement of Doppler and channel estimation which applied to underwater mobile communication with orthogonal frequency division multiplexing (OFDM) technology, a PN sequence based method for Doppler and channel estimation is proposed, an underwater acoustic OFDM communication system structure is given and a block data frame based on PN sequence is designed. For the Doppler estimation and compensation, a delay cross-correlation method is adopted to estimate and compensate the Doppler factor by utilizing the orthogonality of PN sequence, and joints PN sequence and cyclic prefix for carrier frequency offset (CFO) estimation and compensation. While in the aspect of channel estimation, decision feedback channel estimation method based on PN sequence is used. Simulation results show the effectiveness of the proposed Doppler and channel estimation method. Compared with the traditional LFM cross-correlation method, the delay cross-correlation method based on PN sequence decreases two orders of magnitude of Doppler factor estimation error. The constellation map of joint CFO estimation based on PN sequence and cyclic prefix is convergent obviously. The decision feedback channel estimation based on PN sequence could obtain about 6dB performance gains.