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大气湍流引起的闪烁效应会严重影响大气光通信系统的性能。自适应判决阈值技术虽然可以有效改善大气光通信系统的误码率(BER),但是难以进行实时应用。提出了一种根据各种参数统计值,将阈值设置为常量的阈值优化方法。主要考虑乘性高斯噪声并假设闪烁满足对数正态分布,分析了湍流信道中大气光通信系统的最优常量阈值,并将数值分析结果与弱湍流条件下的实验数据进行对比。对比的结果显示,最优常量阈值方法是有效可行的,相对于自适应阈值的性能降低也是可以接受的。分析还显示,在忽略孔径平均效应条件下,最优常量阈值主要取决于对数光强起伏方差和平均接收光功率,而其他参数的影响基本可以忽略。基于分析结果,提出了可以在实际应用中估计最优常量阈值的非线性模型。
The flickering effect caused by atmospheric turbulence can seriously affect the performance of atmospheric optical communication system. Although the adaptive decision threshold technique can effectively improve the bit error rate (BER) of the atmospheric optical communication system, it is difficult to apply it in real time. A threshold optimization method based on the statistical values of various parameters and setting the threshold as a constant is proposed. Mainly considering the multiplicative Gaussian noise and assuming that the flicker meets the logarithm normal distribution, the optimal constant threshold of the atmospheric optical communication system in turbulent channel is analyzed. The numerical analysis is compared with the experimental data under weak turbulence. The comparison results show that the optimal constant threshold method is effective and feasible, and the performance reduction relative to the adaptive threshold is also acceptable. The analysis also shows that under the condition of neglecting the average aperture, the optimum constant threshold mainly depends on the logarithm of the undulation variance of light intensity and the average received light power, while the influence of other parameters can be neglected. Based on the analysis results, a nonlinear model which can estimate the optimal constant threshold in practical application is proposed.