残差神经网络辅助的快时变多径信道估计方法

Residual Neural Network-Assisted Fast Time-Varying Multipath Channel Estimation Method

  • 摘要: 在快时变多径信道环境中,正交频分复用(Orthogonal Frequency-Division Multiplexing, OFDM)系统的信道估计一直是一个颇具挑战性的问题。传统的过采样复指数基扩展模型(Oversampling Complex Exponential Basis expansion models, OCE-BEM)虽然能够在一定程度上减小多普勒频移带来的子载波间干扰(Inter-Carrier Interference, ICI),但其抗噪声能力较弱,并且存在固有的模型误差,这在很大程度上限制了其在复杂通信场景中的应用。为了解决上述问题,本文提出了一种残差神经网络辅助的信道估计方法。该方法将数据拟合问题转换为图像去噪问题,将信道冲激响应的估计值视为原始图像,真实值视为去噪后的图像,通过构建两者之间的数据映射关系来减小估计值与真实值之间的差异。本文所提信道估计方法用一个残差神经网络去除OCE-BEM最小二乘估计结果中引入的噪声误差,充分发挥神经网络的数据拟合作用,通过构建信道估计值与真实值的映射关系来减小BEM的固有建模误差。同时,所提信道估计方法将输入输出数据的虚部和实部进行了结合,最大限度地保留了信道的幅度和相位信息。在网络结构的设计上,本文选用的残差结构能够增强网络特征提取能力,同时防止训练过程中梯度消失和梯度爆炸现象的出现,进而提高网络的稳定性和收敛速度。仿真结果表明,在不同的信噪比和多普勒条件下,与传统的BEM估计方法相比,本文所提信道估计方法表现出了更优异的估计性能。

     

    Abstract: ‍ ‍In fast time-varying multipath channel environments, channel estimation for Orthogonal Frequency-Division Multiplexing (OFDM) systems remains a challenging problem. Traditional Oversampling Complex Exponential Basis Expansion Models (OCE-BEM), despite their ability to mitigate Inter-Carrier Interference (ICI) arising from Doppler shifts to some extent, are plagued by inadequate noise resistance and inherent modeling inaccuracies, severely limiting their applicability in complex communication environments. To overcome these hurdles, this paper introduces a novel channel estimation method that leverages a residual neural network. This method recasts the data fitting problem as an image denoising task, wherein the estimated channel impulse response is regarded as the original image and the true value as the denoised image. By constructing a data mapping relationship between the two, the discrepancy between the estimated and true values is effectively reduced. The proposed method deploys a residual neural network to eliminate noise errors introduced by the least squares estimation results of OCE-BEM. It fully exploits the data fitting capabilities of neural networks to mitigate the inherent modeling errors of BEM by establishing a robust mapping between the estimated and true channel values. Moreover, the method integrates the real and imaginary parts of the input and output data, thereby preserving the channel’s amplitude and phase information to the fullest extent. In the design of the network architecture, the employed residual structure not only enhances the network’s feature extraction capabilities but also effectively prevents gradient vanishing and gradient explosion during the training process, thus improving network stability and accelerating convergence. Simulation results demonstrate that the proposed method consistently exhibits superior estimation performance compared to conventional BEM estimation methods across a range of signal-to-noise ratios and Doppler conditions.

     

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