远程水声扩频通信时变多普勒估计与码片同步联合处理算法

在低信噪比的远程浅海水声移动通信中,传统多普勒估计算法难以有效跟踪时变多普勒因子,针对该问题提出了一种基于时频联合搜索的新的时变多普勒跟踪算法。利用正交支路扩频码的扩频增益和互相关特性,结合迭代处理技术,搜索扩频码符号在不同码片相位下的多普勒频谱峰值,选择具有最大峰值的频谱对应的多普勒因子和码片相位,对信号进行多普勒补偿和码片同步。蒙特卡洛仿真表明,该算法能够在信噪比为-18 dB的情况下有效地对10 m.s~(-1)以内产生的时变多普勒进行逐符号跟踪补偿。算法经过海试测试,在远程浅海移动通信中成功完成了多普勒跟踪估计,通信误码率达到10~(-3)。

Joint processing for time-variant Doppler estimation and chip synchronization in long-range underwater acoustic spread spectrum communication

To overcome the disadvantages of conventional Doppler estimation under long range shallow water, a novel algorithm based on joint time-frequency search is proposed to track the time-variant Doppler and chip phase in underwater acoustic spread spectrum communication. The algorithm utilizes the spread spectrum gain and cross-correlation of orthogonal spreading code combined with iterative processing to search the Doppler spectrum peak under different chip phases. Then the correct Doppler factor and chip phase corresponding to the spectrum with the maximum peak value are selected to perform the Doppler compensation of signal and the chip synchronization. Experiment results performed by Monte Carlo simulation are provided to demonstrate that the proposed algorithm can effectively track the time-variant Doppler factor within 10 m·s^-1 under the SNR of -18 dB. The sea-trial results show successful Doppler tracking and estimation in the long range underwater acoustic spread spectrum mobile communication with a stable performance of BER=10^-3.