Strong correlation of link gains over multiple wavelengths has been demonstrated in non-line-of-sight optical wireless scattering communication. In this paper, we further demonstrate the strong correlation of the channel impulse responses for different wavelengths. A novel channel estimation method is proposed based on such correlation, where only certain reference wavelengths are assigned with pilot signals. On each channel assigned by the pilot signal, we adopt an improved least-squares method to estimate the channel tap coefficients and the tap length. The channel tap coefficients for other wavelengths can be estimated based on the inter-wavelength correlation. Under the proposed channel estimation, the channel estimation accuracy can be improved as shown by the simulations. We further propose an optimization method for the correlation-based channel estimation pilot pattern based on the receiver channel state feedback. Simulation results show that optimized pilot pattern can achieve significant performance gain over the fixed pilot pattern. Moreover, the channel estimation performance is insensitive to the channel state feedback frequency.

中文翻译：

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用于多波长光散射 NLOS 通信的基于相关的 LTI 信道估计

在非视距光无线散射通信中已经证明了多个波长上链路增益的强相关性。在本文中，我们进一步证明了不同波长的信道脉冲响应的强相关性。基于这种相关性，提出了一种新的信道估计方法，其中只为某些参考波长分配导频信号。在导频信号分配的每个信道上，我们采用改进的最小二乘法估计信道抽头系数和抽头长度。其他波长的信道抽头系数可以基于波长间相关性来估计。在所提出的信道估计下，信道估计精度可以提高，如仿真所示。我们进一步提出了一种基于接收器信道状态反馈的基于相关的信道估计导频模式的优化方法。仿真结果表明，优化的导频模式可以比固定导频模式获得显着的性能增益。此外，信道估计性能对信道状态反馈频率不敏感。