An Improved Delay Estimation Algorithm for Underwater Acoustic OFDM Sparse Channel
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摘要: 水声正交频分复用(OFDM)系统中,采用传统正交匹配追踪(OMP)方法估计离网格(off-grid)时延时,需要很高的过采样因子和高昂的计算开销。针对传统OMP方法估计离网格时延计算复杂度高的问题,该文借鉴多元线性拟合思想引入路径补偿的概念,提出了一种基于路径补偿的改进OMP时延估计算法,用以补偿从离网格路径向其周围网格位置泄漏的能量,并用补偿距离这一参数来解释路径补偿效果。该算法无需增加过采样因子,仅利用恰当的补偿距离即可实现较好的估计效果,且能在提高估计性能的同时降低计算复杂度。仿真分析与海试结果验证了该方法的优越性。Abstract: Traditional Orthogonal Matching Pursuit (OMP) method needs high oversampling factor and computational overhead to estimate off-grid path delays in underwater acoustic Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, the idea of path compensation is introduced from multiple linear fitting theory, and an improved OMP path delay estimation method based on path compensation is proposed to reduce the energy leaking from off-grid paths to its surrounding grids. The compensation distance is used to evaluate compensation effect. The improved algorithm can improve the estimation performance by appropriate compensation distance without increasing the oversampling factor. Compared with the traditional OMP method, the proposed algorithm has lower computational complexity but better estimation performance. The results of simulations and sea trial data decoding show the superiority of the proposed method.
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表 1 内积计算复杂度定性对比
实数乘法 实数加法 OMP-grid-comp $L \cdot 2\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ $L \cdot 3\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ OMP-normal-comp $2L \cdot 2\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ $2L \cdot 3\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ OMP-sin $2L \cdot 2\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ $2L \cdot 3\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ SdMP $L \cdot 2\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ $L \cdot 3\lambda {N_{\rm{P}}}{\log _2}\lambda {N_{\rm{P}}}$ 表 2 内积计算复杂度定量对比
实数乘法 实数加法 OMP-grid-comp($\lambda = 4$) 102400 153600 OMP-normal-comp($\lambda = 4$) 204800 307200 OMP-sin($\lambda = 4$) 204800 307200 SdMP($\lambda = 4$) 102400 153600 表 3 不同信道估计方法的原始误码率
误码率 阵列1 阵列2 阵列3 阵列4 阵列5 本文方法 最大值 0.0568 0.0682 0.0483 0.0710 0.0284 平均值 0.0045 0.0120 0.0049 0.0058 0.0070 OMP-2grid-comp 最大值 0.0625 0.0682 0.0483 0.0739 0.0369 平均值 0.0057 0.0128 0.0063 0.0065 0.0079 OMP-sin 最大值 0.0597 0.0824 0.0540 0.0767 0.0313 平均值 0.0053 0.0146 0.0062 0.0077 0.0080 SdMP 最大值 0.0568 0.0710 0.0597 0.0795 0.0426 平均值 0.0053 0.0127 0.0072 0.0082 0.0079 OMP-normal-comp-8 最大值 0.0568 0.0795 0.0597 0.0824 0.0426 平均值 0.0054 0.0159 0.0067 0.0084 0.0100 -
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