Mutual Interference Assessment Between BeiDou RDSS And Iridium Satellite System

The Bei Dou Navigation Satellite System(BDS)integrates Radio Navigation Satellite Service(RNSS)and Radio Determination Satellite Service(RDSS).It can provides the user with basic navigation function and short message service.To promote the application of BDS airborne equipment on civil aircraft will be faced with compatibility analysis with other loaded equipment.Iridium Satellite System has been integrated and applied in the main aircraft types of Airbus and Boeing to provide aeronautical mobile satellite services for aircraft.The user link of Iridium Satellite System partially overlaps with the uplink spectrum of RDSS,and there are scenes of interference coexistence between systems.Therefore,this paper evaluates and analyzes the mutual interference between Bei Dou RDSS and Iridium system.The main contents are as follows:First of all,the problem of frequency sharing between Bei Dou RDSS and Iridium system is described in this thesis.The system overview,composition,communication schemes,signal structure and spectral characteristics of the two systems are summarized and analyzed.Secondly,the propagation link model of ground-to-air link is established from the aspects of free space propagation,atmospheric gas absorption,rainfall,other precipitation,cloud,troposphere and ionospheric scintillation.By comparing the signal propagation characteristics of the two systems,the corresponding link loss and link budget are given.Then,the interference link for evaluation is established by constructing the interference coexistence scenario between Bei Dou RDSS and Iridium system.Evaluating the compatibility between Bei Dou RDSS airborne equipment and Iridium airborne earth station.Through the simulation and calculation of the isolation between the two antennas on the cylindrical fuselage model,the influence of factors such as the layout of the airborne antenna,the shielding effect of the aircraft fuselage,and the cross-polarization loss on the antenna isolation is considered.According to the evaluation results,the reasonable antenna layout,RDSS transmission power,antenna polarization axis ratio requirements and methods to improve airborne antenna isolation are given.Finally,the interference from ground terminal to satellite uplink is evaluated,the evaluated interference links include the interference from the Bei Dou RDSS ground terminal to Iridium uplink and the interference from the Iridium earth station to the uplink of the Bei Dou RDSS.According to the system parameters,link model and interference evaluation criteria,the uplink interference is evaluated,and the interference evaluation results are given.