Analysis And Evaluation Of BDS Application Performance Under Complex Terrain And Electromagnetic Interference Conditions

Under the background that the Beidou regional system has been opened and the BDS-III has entered the comprehensive construction,the capability of system performance evaluation and analysis is extremely important to the development of the related industrial application.However,the existing methods of performance analysis and evaluation lack consideration of complex terrain and electromagnetic environment.In this regard,this paper focuses on the application performance analysis method of Beidou satellite navigation system,which influenced by complex terrain and electromagnetic interference.The details are as follows.In the first part,to solve the problem that the actual terrain is not considered in the current performance evaluation of Beidou system,a performance analysis model of satellite navigation system in complex terrain environment is proposed.The validity of the model is verified by comparing the measured data and the calculated results under several typical scenes.In the second part,the influence of different topographic conditions on the performance of RNSS/RDSS is studied by using the analysis model proposed in this paper.Taking Zhangjiajie Scenic Area as an example,the calculation results show that in areas with large slope,the PDOP value will change from less than 3 when terrain is not considered to 6 or more after considering the terrain,and the availability of the system will also change from more than 95%to less than 80%.In the relatively flat terrain,there is no significant change in the system performance before and after the terrain.This result indicates that the influence of the terrain on the application performance of the Beidou system cannot be ignored in the complex mountainous environment with large terrain fluctuations.On the other hand,the paper not only analyzes the influence of terrain on the connectivity of RDSS satellites,but also puts forward a RDSS positioning performance evaluation method,which based on the weighted precision factor,to solve the mismatch between the positioning accuracy evaluation results and the actual situation caused by neglecting the difference between elevation error and ranging error.Compared with the traditional method,the positioning accuracy predicted by the weighted precision factor is closer to the actual results,which reflects the better performance prediction ability.The third part studies the influence of electromagnetic interference on the performance of Beidou RDSS system and the corresponding countermeasures.Aiming at the problem that the RDSS system can not provide services under malicious jamming conditions,a method of locating interference sources based on time-frequency difference is proposed.The simulation results show that the locating accuracy of interference sources in China and its surrounding areas can reach less than 3 kilometers when the time difference and frequency difference measurement accuracy are 10^-6seconds and 1Hz,respectively.This result will effectively improve the ability of relevant personnel to quickly dispose of malicious interference.Aiming at the problem that the reduction of carrier-to-noise ratio of RDSS signal caused by unintentional interference leads to the decrease of ranging accuracy,this paper explores the application of user doppler frequency observation to the time-frequency joint positioning of RDSS.It is found that the joint positioning method can not significantly improve the positioning performance of RDSS under the condition of the existing frequency measurement accuracy.Nevertheless,the service range of the system during the transition from 5GEO to 3GEO can be effectively improved by reducing the number of satellites needed for positioning.