一种改进的水声信道载波恢复盲均衡算法

Improved super-exponential iteration blind equalization algorithm for carrier phase recovery in underwater acoustic channels

针对超指数迭代判决反馈盲均衡算法在水声通信系统中表现出收敛性差的问题,提出了一种带二阶锁相环的改进超指数迭代判决反馈盲均衡算法.该算法基于对修正超指数迭代算法误差函数的分析,提出了一种新的、能够快速收敛的误差函数,并有效提高了载波恢复能力;在判决反馈均衡器中引入二阶数字锁相环,实现对相位旋转的跟踪和补偿,从而实现对原始发射信号的正确恢复.在两种水声信道条件下,采用两种调制信号分别对算法的收敛性能和载波恢复性能进行了计算机仿真,结果表明:在混合相位信道环境中,新算法相比超指数迭代判决反馈算法在均方误差、收敛速度上得到很大改善;在具有相位旋转的信道环境中,新算法实现了对相位旋转的有效补偿,改善了载波恢复性能.

An improved super-exponential iteration decision feedback blind equalization algorithm with the second order digital phase-locked loop（NMSEI-DFE-2DPLL） is proposed in order to overcome the problem of the ill convergence performance of the super-exponential iteration decision feedback algorithm in the underwater acoustic communication system.Based on the analysis of the modified super-exponential iteration error function,a new fast convergence error function is presented which increases carrier recovery ability;a second order digital phase-locked loop is introduced in decision feedback equalization to track and compensate phase rotation,carrying out the transmitted sequence recovery.Computer simulations of the new algorithm about convergence and carrier recovery ability are carried out respectively under two underwater acoustic channels,using two modulation signals.Simulation results demonstrate that the mean square error and convergence rate of the proposed algorithm have been improved to a large extent compared with the SEI-DFE algorithm in mixed phase channel environment,and the phase rotation has been compensated and carrier recovery ability has been improved greatly in channel environment with phase rotation.