车体垂向振动对高铁FSO通信性能影响的研究

Study on impact of carriage vertical vibration on high-speedtrain FSO communication performance

为了将自由空间光(free space optical,FSO)通信技术应用于高速铁路通信,研究车体垂向振动对FSO通信性能的影响。首先,根据轨道不平顺功率谱密度函数推导其在频域的关系表达式,并利用逆傅里叶变换法对轨道不平顺进行仿真;然后,根据1/4车体4自由度模型的微分方程,利用拉普拉斯变换推导传递函数搭建基于传递函数的Simulink仿真模型;最后,通过对车体垂向位移的仿真,推导其概率密度函数表达式,并在高速铁路FSO通信链路中应用动态束腰控制方案,即在发射端实时调整束腰。仿真结果验证了车体垂向位移的概率密度函数表达式,证明动态束腰控制方案在高速铁路FSO通信链路中性能优于传统的固定束腰控制方案。因此,车体垂向位移的概率密度函数和动态束腰控制方案可为高铁FSO通信研究提供理论基础。

To apply FSO(free space optical)communication technology to HST(high-speed train)communication,the impact of carriage vertical vibration on FSO communication performance has been explored.Firstly,the expression of track irregularity in frequency domain was derived in accordance by virtue of the spectral density function of track irregularity,and the inverse Fourier transform method was used to simulate the track irregularity.Secondly,based on the differential equation of the 1/4 carriage model with 4 degrees of freedom,the transfer function was derived using Laplace transform,thereupon establishing the Simulink simulation model.Finally,the PDF(probability density function)was derived by simulatingthe vertical displacement of carriage.And the dynamic beam waist adjustment was applied to the transmitter of HST FSO communication link,where the beam waist was adjusted in real-time at the transmitter.Simulation results verify the PDF expression of the carriage vertical displacement and prove the performance advantage of the dynamic beam waist adjustment scheme over the conventional fixed beam waist adjustment scheme in HST FSO communication link.The PDF of carriage vertical displacement and the dynamic beam waist adjustment scheme can provide a theoretical basis for the study of high-speed train FSO communication.