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研究了QPSK副载波调制下乘性噪声与加性噪声对接收端星座图影响。基于GammaGamma信道模型,分析了乘性噪声和加性噪声影响下系统的接收星座图。通过仿真实验计算了混合噪声情况下的星座图分布以及接收端功率谱密度。讨论了混合噪声条件下,不同能见度、传输距离对系统误码率的影响。结果表明:随着湍流强度的增强,接收端功率谱存在明显的展宽迹象;不同加性噪声条件下,当能见度小于传输距离时,气溶胶粒子散射为影响通信的主要因素。不同乘性噪声条件下,当能见度处于0.5~1.5 km时,乘性噪声会影响接收光强,进一步增大系统误码率。文中工作对真实环境下降低无线激光通信的误码率和提高通信质量有重要意义。
The effect of multiplicative noise and additive noise on the receive side constellation of QPSK subcarrier modulation is studied. Based on the GammaGamma channel model, the receiving constellation of the system under the influence of multiplicative noise and additive noise is analyzed. The distribution of constellation and power spectral density at the receiver are calculated by simulation experiment. The effect of different visibility and transmission distance on the BER is discussed under mixed noise conditions. The results show that with the increase of turbulence intensity, there is a clear sign of broadening the power spectrum at the receiving end. Under different additive noise conditions, when the visibility is less than the transmission distance, the scattering of aerosol particles is the main factor affecting the communication. Under different multiplicative noise conditions, when the visibility is between 0.5 and 1.5 km, the multiplicative noise will affect the received light intensity and further increase the system error rate. The work in this paper is of great significance to reduce the bit error rate of wireless laser communication and improve the communication quality under the real environment.