一种针对小多普勒扩展水声信道的OFDM接收算法

An OFDM Receiver Algorithm for Underwater Acoustic Channels with Small Doppler Spread

摘要:

在水声正交频分复用（OFDM）通信系统中，水声信道中的多径时延扩展会带来频域选择性衰落，多普勒效应会带来子载波间干扰（ICI）。传统接收算法需要开展复杂的二维（时延/多普勒）信道估计，再进行复杂的信道均衡和符号检测。针对有限多普勒扩展的信道条件下多普勒矩阵元素变化缓慢、ICI干扰范围有限的特点，该文借鉴多项式拟合思想，提出了一种创新的接收算法。该算法将多普勒矩阵元素近似为多项式函数，迭代进行多项式拟合和数据符号频域均衡。和传统方法相比，该算法无需进行信道多普勒估计，仅需信道的一维（时延）估计即可实现较好的性能。利用Bellhop产生的水声信道仿真结果验证了该算法的可行性。

Abstract:

Underwater acoustic Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from frequency-selective fading and inter-carrier interference (ICI) caused by the underwater acoustic channel. Conventional reception algorithms choose to carry out complex two-dimensional channel estimation, followed by complex channel equalization and symbol detection. Targeting at the characteristics of slow change of Doppler matrix elements and limited ICI interference range in the channels with limited Doppler spread, this paper proposes an innovative receiver algorithm. The algorithm approximates the Doppler matrix elements with polynomial functions, and iteratively performs polynomial fitting and frequency domain equalization. Compared with traditional methods, the algorithm does not require Doppler estimation of the channel. Instead, it only requires one-dimensional (time delay) estimation of the channel to achieve good performance. The feasibility of the algorithm is verified by the simulation results in underwater acoustic channel generated by Bellhop.