基于最小均方自适应滤波器的无线光通信接收性能分析

Performance Analysis of the Reception Based on Least-Mean-Square Adaptive Algorithm in Optical Wireless Communication System

无线光通信(OWC)系统采用大气通道作为传输媒介,而大气湍流效应引入了与信号强度有关的乘性噪声。为了消除乘性噪声所引起的信号衰落,分析并给出了基于最小均方(LMS)自适应滤波器的判决门限更新算法和稳态的抽头权系数相关矩阵算法。通过理论分析和计算机仿真,讨论了最小均方滤波器及其参数对无线光通信接收性能的影响。结果表明,采用非因果滤波器的无线光通信系统对湍流噪声具有明显的抑制作用。在弱湍流情况下,基于自适应最小均方滤波器的系统误码率(BER)低于10-8,可以满足网络通信的要求。通过分析不同滤波器阶数对误码率的影响表明,所采用的255阶的非因果结构的最小均方滤波器是最优的结构。

Optical wireless communication （OWC） systems use the atmosphere as a propagation medium, so the atmospheric turbulence effects lead to multiplicative noise related with signal intensity. In order to suppress the signal fading induced by multiplicative noise, the decision threshold-updating algorithm based on least-mean-square （LMS） adaptive filter is introduced and investigated. An accurate expression for the steady-state tap-weight covariance matrix is derived for the real LMS algorithm. The effect of the parameters in LMS algorithm on OWC system performance was introduced through theoretical analysis and computer simulation. It is shown that in the OWC system with non-causal filter the turbulence effect has been apparently abated. The bit error ratio （BER） of the system over weak turbulence based on adaptive filter is below 10^-8, which can satisfy the communication requirement. The 255 order non-causal structure of LMS filter is the optimal structure.