| At present,4G/LTE is a mainstream commercial mobile communications network.The proportion of LTE base stations has exceeded half of the total number of base stations.The safety compliance assessment of LTE base station electromagnetic radiation exposure levels is particularly important.The downlink channels of FDD-LTE mainly include a PDSCH(Physical Downlink Shared Channel),a PDCCH(Physical Downlink Control Channel),and a PBCH(Physical Broadcast Channel).Downlink signals include a synchronization signal and a reference signal.At present,research on electromagnetic radiation exposure prediction of FDD-LTE base stations at domestic and foreign mainly predicts the maximum electromagnetic radiation through the fixed transmission PBCH channel,does not consider the PDSCH channel and PDCCH channel that vary with the base station traffic,and the electromagnetic radiation prediction results obtained are not accurate enough.At the same time,in the research of exposure measurement of FDD-LTE base stations,the center frequency of the downlink bandwidth is mainly measured to evaluate the exposure of the entire bandwidth.Because of the adaptive adjustment technology of FDD-LTE links,there is a large difference in electromagnetic radiation at different frequencies.Measuring only part of the frequency of electromagnetic radiation exposure is inaccurate.The main content and innovation of this paper are as follows:(1)In the research of electromagnetic radiation prediction of FDD-LTE base stations,this paper proposes a method of electromagnetic radiation prediction for FDD-LTE base stations based on the queuing model.This method establishes the calculation method of the PDSCH channel's sending duty ratio based on the data traffic queuing model based on the Markov-modulated Poisson process,and calculates the sending duty ratio of the PDCCH channel by controlling the channel unit batch arrival queuing model.A method for calculating the transmission duty cycle of the fixedly transmitted PBCH channel,the reference signal and the synchronization signal is issued,and the electromagnetic radiation intensity of the base station is predicted based on the duty cycle of the FDD-LTE signal transmission.In this paper,three sub-bands with different frequencies are chosen as experimental objects.The calculated values of the transmitted duty cycle and the predicted values of electromagnetic radiation are verified.The experimental results show that the prediction accuracy of the electromagnetic radiation prediction value obtained by this method is 0.016.The method can effectively predict electromagnetic radiation of FDD-LTE base stations.(2)In the field of electromagnetic radiation measurement of FDD-LTE base stations,this paper proposes an electromagnetic radiation measurement method for FDD-LTE base stations.The method is based on the characteristics of FDD-LTE downlink signals in the time domain and frequency domain.The downlink bandwidth of FDD-LTE base station is divided into sub-bands,and the electromagnetic radiation of each sub-band is measured to optimize the parameter setting of the spectrum analyzer.In order to improve the measurement accuracy,the confidence interval of electromagnetic radiation is calculated by combining the spectrum analyzer to measure the uncertainty of the mixed standard,and the electromagnetic radiation of all the sub-bands is integrated to obtain the overall electromagnetic radiation level of the base station.The measurement experiment performed 24-hour continuous measurement and one-week statistics on FDD-LTE base stations in two different operating bands.Through the analysis of the measurement results,the electromagnetic radiation of FDD-LTE base stations varies greatly at different frequencies and at different times,but the probability density distribution of electromagnetic radiation among different base stations has certain similarities.This article proposes a measurement method to more accurately assess the actual electromagnetic radiation intensity of FDD-LTE base stations. |
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