基于非均匀快速傅里叶变换的正交频分复用水声通信多普勒估计与补偿方法

Doppler estimation and compensation method for orthogonal frequency division multiplexing underwater acoustic communication based on non-uniform fast Fourier transform

针对正交频分复用水声通信对多普勒频移敏感的问题,提出了一种基于非均匀快速傅里叶变换的正交频分复用水声通信多普勒估计与补偿算法。将第2类非均匀快速傅里叶变换引入正交频分复用水声通信中,利用非均匀快速傅里叶变换对接收信号进行多普勒因子网格补偿,通过稀疏贝叶斯学习获得水声信道估计,以水声信道的稀疏能量最小作为多普勒因子判断准则,从而获得高精度多普勒估计。仿真结果显示,所提出的方法在信噪比大于5 dB时,多普勒估计均方根误差优于1×10^(-5),同时系统误码率随着多普勒估计均方根误差减小而降低。海上试验结果显示,利用本文所给多普勒估计方法获得的两船相对径向速度与实际情况相吻合,系统解码后的平均误码率优于8.33×10^(-4)。仿真和海上试验结果表明,所提出的算法能够对多普勒因子进行有效估计,并且降低系统误码率。

Aiming at the problem that the orthogonal frequency division multiplexing(OFDM) underwater acoustic communication is sensitive to Doppler frequency shift, a Doppler estimation and compensation algorithm for OFDM underwater acoustic communication based on non-uniform fast Fourier transform(NUFFT) is proposed. The type-2 NUFFT technique is introduced into the OFDM underwater acoustic communication and utilized to perform Doppler factor grid compensation on the received signal. And the estimation of underwater acoustic channel is obtained through the sparse Bayesian learning. Then the minimum sparse energy of the underwater acoustic channel is used as the Doppler factor judgment criterion to obtain a high-precision Doppler estimation. Simulation results show that when the signal to noise ratio(SNR) is greater than 5 dB, the root mean squared error(RMSE) of the proposed method is better than 1×10^(-5). And the bit error rate(BER) of the system decreases with the decrease of the RMSE of Doppler estimation. The results of the sea trial show that the relative radial velocity between the two ships obtained with the proposed Doppler estimation method is consistent with the actual situation. And the average BER after decoding is better than 8.33×10^(-4). Simulation and sea trial results demonstrate that the proposed algorithm can effectively estimate Doppler factor and reduce the system bit error rate.