一种适用于高阶QAM信号的水声信道盲均衡算法  

Making Blind Algorithm of Multipath Fading Underwater Acoustic Channels Suitable for High Order QAM Signals

作　　者：孙丽君[1] 孙超[1] 

机构地区：[1]西北工业大学声学工程研究所

出　　处：《西北工业大学学报》2005年第5期598-601,共4页Journal of Northwestern Polytechnical University

摘　　要：目前,盲均衡是水声通信领域中的热点问题。针对多径衰落水声信道的均衡问题,提出了一种修正的超指数迭代盲均衡算法,该算法可校正水声信道引入的载波相位旋转。在收敛阶段采用该算法,之后根据某一切换准则,切换到判决导引算法,可有效减小超指数迭代算法对高阶正交幅度调制信号的剩余均方误差。仿真结果表明,该算法有效纠正了载波相位旋转,并获得了较快的收敛速度和较小的稳态误差,提高了水声通信的质量,因而具有良好的工程应用价值。The full paper begins with a detailed analysis of the difficulties encountered in trying to make blind algorithm suitable for high order QAM （quadrature amplitude modulation） signals. These difficulties are： （1） the MSE （mean square error） of SEI （super-exponential iterative） blind equalization algorithm is too large; （2） switching from SEI blind equalization algorithm to DD （decision directed） blind equalization algorithm, which can give small MSE, is quite often made impossible due to the phase rotation in the equalizer output caused by the phase fluctuation when there exists phase residual in the carrier frequency. We aim to overcome these two difficulties, thus making blind algorithm suitable for high order QAM signals. For the blind equalization problem in muhipath fading underwater acoustic channels, we proposed MSEI （modified SEI） blind equalization algorithm and it is capable of correcting phase rotation of the carrier frequency. At the beginning of the iteration process, the MSEI algorithm is used. When MSE level is reduced to a certain level, the iteration process switches to the decision directed （DD） algorithm, which can achieve less residual MSE for high order QAM signals. The full paper derives the MSEI algorithm in detail and explains the reason why it can correct the carrier phase rotation. Then the full paper gives the base band model of the switch scheme as well as the exchange criterion and then outlines the iteration process of the proposed algorithm. Finally the full paper gives computer simulation results for high order QAM signals, after 10 000 iterations, the MSE for SEI algorithm plus DD algorithm is about -6 dB and the MSE for MSEI algorithm is about -11 dB; but the MSE for MSEI algorithm plus DD algorithm reaches about -18 dB only after 4000 iterations.

关 键 词：水声通信 盲均衡 超指数 判决导引 

分 类 号：TN911.5[电子电信—通信与信息系统]