中文摘要：

建立适用于OFDM水声通信信号的信道估计模型，对MP算法进行改进，引入路径门限调整机制克服虚假路径造成的不良影响，通过重要路径权系数的迭代修正降低非正交性引入的估计误差，以较小计算量取得了与OMP算法相当的估计精度；针对传统信道估计算法对信道长度信息的依赖问题，提出了一种信道长度自适应信道估计算法，该算法能够对信道估计质量进行实时评价，并根据评价结果实现信道估计算法预估信道长度的自适应调整，满足未知水声信道精确估计及通信应用的需要；基于OFDM导频元素个数与信道估计效果的关系研究，提出了OFDM导频序列自调整的通信方案，以较小的带宽损失保证了可靠的水声通信。通过仿真和实地试验，验证了该文研究内容的有效性。

英文摘要：

The channel estimation model suitable for underwater acoustic OFDM communication signals is studied in this paper. Based on the analysis of existing channel estimation algorithms, the matching pursuit （MP） algorithm was improved by introducing a threshold adjusting mechanism which can effectively avoid false paths. An iterative correction method is used to decrease the estimation error caused by non-orthogonality. The improved MP algorithm can achieve a comparative estimation precision with OMP, but has smaller computation amount. In order to overcome the dependences on the information of channel’s length, a new channel estimation algorithm is proposed to adjust pre-estimated channel length automatically based on the real-time evaluation of channel estimation’s quality. Besides, the relations between the number of pilots and channel estimation effects are studied and a self-adjusting OFDM underwater acoustic communication scheme is presented for achieving reliable communication with lesser bandwidth recourse losses. The correctness and validity of the presented results are validated by simulations and experiments.