Research On The Performance Of Millimeter-wave Communication Under Rainfall Environment

As the foundation of the fifth-generation mobile communication(5G),millimeter-wave communication has abundant spectrum resources,which can meet the requirements of high capacity,high speed and low delay of the system.However,the frequency of the millimeter wave band is relatively high.It will be affected by the atmospheric environment during the communication process,especially the rainfall will cause serious attenuation of the millimeter wave signal.Therefore,it is necessary to study the dynamic rain attenuation and the technology of resisting rain attenuation on the millimeter wave propagation link.Adaptive Modulation and Coding(ACM)technology,as one of the key technologies to resist rain attenuation,can improve the transmission rate as much as possible while ensuring the reliability of transmission data.Therefore,it is necessary to plan and design the millimeterwave communication system reasonably,and estimate the impact of rainfall on the performance of the millimeter-wave communication,so as to ensure the normal operation of the communication system.The main contents of this dissertation are as follows:1、The rainfall observation data in Beijing and Haikou for many years are statistical analysis.It shows that the Weibull distribution has a wider application range than the lognormal distribution and the gamma distribution,and has a better fit to the measured data.Based on the Weibull distribution model of rainfall rate,combined with the equivalent path model of ITU millimeter wave rainfall attenuation,a channel state prediction model of millimeter wave rainfall attenuation link is proposed,which can better predict the rainfall attenuation channel of 5G links in different regions and frequencies.Using the rain attenuation channel state of the millimeter wave link,the communication performance under the millimeter wave rain environment is studied,including the average bit error rate,the average signal-to-noise ratio,the channel capacity and the interruption probability.It provides some reference for the design and performance evaluation of millimeter wave communication system link.2、According to the Weibull distribution model of rain attenuation of millimeter-wave links,the generation method of rainfall attenuation data in the absence of measured data is given combined with the EMB rain attenuation time series model.And the dynamic rain attenuation time series at different frequencies in Beijing and Haikou are simulated.The fast Fourier transform and Kaiser Window function are used to estimate the time series power spectrum,which is consistent with the theoretical results,indicating that the time series generated by this method can better simulate the dynamic attenuation characteristics.Through multiple simulations of rain attenuation and statistical analysis,the probability distribution of rainfall attenuation can be obtained.Compared with the ITU-R model,it shows that the rain attenuation time series model generated by the simulation can be used to predict rain attenuation and analyze link performance in 5G millimeter wave communication.3、Adaptive modulation and coding technology can effectively alleviate the impact of rainfall on millimeter-wave links.In this dissertation,MQAM modulation and convolutional coding are mainly used as modulation and coding schemes(MCS)of millimeter-wave communication systems.And the bit error rate performance under different MCS is calculated and analyzed.Combined with the millimeter-wave rain attenuation channel model,according to the principle of maximizing spectrum utilization in ACM technology,for a specific target bit error rate,the MCS based on the link rain attenuation adaptive system is constructed.And the adaptive MCS conversion algorithm in the communication system is given.In order to consider update of Channel State Information(CSI)in time and the system power consumption,an update time model and algorithm are proposed based on the rainfall attenuation time series data and the transition probability of rainfall attenuation.Compared with the traditional transmission scheme,the adaptive MCS can effectively improve the data transmission rate,ensure the stability of the communication system,and provide a certain reference for resisting rain attenuation design of the millimeter wave communication system.