一种水声通信Turbo均衡中的软迭代信道估计算法

 Turbo均衡技术是水声相干通信克服信道多径、消除码间干扰(ISI)的有效工具。Turbo均衡实际使用时需要对时变、多径信道进行良好的估计。为了提高信道估计的效果，该文基于时变横向滤波和相位旋转信道模型，提出一种水声通信Turbo均衡中的软迭代信道估计算法。该算法采用快速自优化最小均方算法得到各数据符号处的横向滤波器系数矢量并与二阶锁相环联合优化计算。通过仿真比较，该算法明显优于硬迭代信道估计算法，且相位估计性能优于其他文献中的软迭代信道估计算法。在海上试验中，水声通信距离5 km，方向近似垂直，接收阵起伏周期10 s，起伏幅度5 m左右，在此情况下进行数据采集。将该算法用于对海试数据的单通道Turbo均衡处理，实现无误码输出，验证了所提算法在软迭代信道相位估计方面的优势。

An Algorithm of Soft Iterative Channel Estimation for Turbo Equalization of Underwater Acoustic Communication

Turbo equalization is the effective method to overcome multipath fading and eliminate Inter-Symbol Interference (ISI) for underwater acoustic coherent communications. In practice, turbo equalization estimates information of time-varying and multi-path channel. In order to improve the performance of channel and phase estimation, an algorithm of combining soft iterative channel and phase estimation for turbo equalization is proposed based on channel mode of time-varying transversal filter and phase rotation. The algorithm adopts soft iterative fast self-optimized LMS to get transversal filter coefficients vector for every symbol and combing it and second-order phase-locked loop for optimization. Through simulation, the proposed algorithm is better than conventional hard decision channel and phase estimation algorithm. As to performance of phase estimation, the proposed algorithm is better than soft iterative channel estimation raised in other references. During the sea experiment, underwater acoustic communication distance is 5 m, approximately in vertical direction and the fuctuation period of receiver array is 10 s. The algorithm is adopted for single-channel Turbo equalization on sea experiment data, which can output error-free symbols. The result verifies the advantage of all of the algorithms in the soft channel estimation.