针对脉冲噪声导致正交频分复用(orthogonal frequency division multiplexing，OFDM)水声通信系统误码率性能降低的问题，提出一种迭代脉冲噪声抑制与信道估计方法。首先，利用对称a稳定(symmetric a sta-ble，SaS)分布对水下噪声进行建模，并通过实测噪声数据进行拟合验证。其次，基于脉冲噪声幅值较大的特性，利用切比雪夫不等式对基带接收信号实部和虚部分别进行脉冲噪声检测和抑制。同时，通过分析最小二乘(least squares，LS)信道估计算法估计误差的统计特性，提出自适应门限LS信道估计算法，减轻残余噪声对信道估计的影响。最后，结合估计的信道和译码结果重构噪声并进行脉冲噪声估计，实现迭代脉冲噪声抑制与信道估计。仿真结果表明，在不同程度脉冲噪声和实测噪声场景下，所提方法能够有效抑制脉冲噪声，显著降低OFDM系统误码率。
Iterative impulsive noise mitigation and channel estimation method for OFDM system
Aiming at the problem that impulsive noise deteriorates the bit error rate performance of orthogonal frequency division multiplexing(OFDM)underwater acoustic communication system,an iterative impulsive noise mitigation and channel estimation method is proposed.Firstly,the symmetric alpha stable(SaS)distribution is introduced to model underwater noise and validated by fitting the measured noise data.Secondly,based on the large amplitude property of the impulsive noise,impulsive noise detection and mitigation are respectively performed on the real and imaginary parts of the received baseband signal by Chebyshev inequality.And through analyzing the statistical characteristics of estimation error of the least squares(LS)channel estimation algorithm,an adaptive threshold LS channel estimation algorithm is proposed to reduce the impact of residual noise.Finally,combining the estimated channel and decoding results to reconstruct noise and estimate impulsive noise,the impulsive noise mitigation and channel estimation are iteratively performed.Simulation results demonstrate that under different levels of impulsive noise and measured noise,the proposed method can effectively suppress impulsive noise and significantly reduce the bit error rate of OFDM system.
underwater acoustic communicationorthogonal frequency division multiplexing(OFDM)impulsive noisechannel estimationiterative estimation
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