The Research Of Approach For Performance Assessment Of BDS-3 Timing And Positioning Based On IGMAS

The Bei Dou Navigation Satellite System(BDS-3)provides all-time,all-weather and high-accuracy positioning,navigation and timing(PNT)services to global users.A hybrid constellation consisting of satellites in three types of orbits was adopted by BDS-3,multi-frequency navigation signals were provided by BDS-3,so that the accuracy of services can be improved by the combination of multi-frequency signals.Currently,the China Satellite Navigation Office has initiated the international GNSS Monitoring and Assessment System(i GMAS)to monitor and assess the performance and operational status of the multi-GNSS satellites.Twenty-eight constellation satellites have been successfully launched by the end of February 2020,these including one Geostationary Earth Orbit(GEO)satellite,24 Medium Earth Orbit(MEO)satellites and three Inclined Geosynchronous Orbit(IGSO)satellites.The BDS-3 has its own characteristics,which compared with other global navigation satellite systems.At present,whether domestic or foreign research on BDS-3 timing and positioning performance is in its infancy.Therefore,it is necessary to research the methods of assessing the performance of timing and positioning services,to provide a reference for the initial performance evaluation of BDS-3.Therefore,this paper mainly assesses the timing and positioning performance of BDS-3,which using the BDS-3 observation data provided by i GMAS.The main research content is as follows:(1)The current construction of BDS-3 was introduced in detail.Additionally,the principles and methods of timing,time transfer,standard point positioning(SPP)and precise point positioning(PPP)based on BDS were summarized.Moreover,the effects of receiver hardware delay and Time Group Delay(TGD)on timing and positioning are further studied.(2)The initial performance evaluation of BDS-3 satellite timing was studied.The timing accuracy of single BDS-3 satellite timing and multi BDS-3 satellite timing under the static model was given.The signals of evaluation include B1 C,B2a,B1 I,and B3 I.The SPP and Bei Dou Global Ionospheric delay correction Model(BDGIM)was used.And,the data of the calibrated receiver were used as a reference.The results show that BDS-3 timing precision was better than 20 ns,and this work provided a reference for the BDS Open Service time accuracy standard.(3)The effect of TGD on pseudorange can reach the meter level,which was an important factor affected the accuracy of navigation positioning and timing.Therefore,TGD must be taken seriously.The TGD parameters of BDS-2 and BDS-3 represented the group delay differential based on B3 I signal.Therefore,the TGD parameters need to be corrected when using another single frequency or dual-frequency ionosphere-free combination.The effect of TGD parameters on SPP for BDS-2 and BDS-3 were studied and analyzed.Moreover,the TGD correction models of BDS-2 and BDS-3 were derived in detail.The results show that after TGD parameter correction the positioning accuracy and positioning service performance of BDS-3 was significantly improved.(4)With the development of BDS-3 precision products,meanwhile,considering that the BDS-3 satellites were equipped with higher-precision atomic clock,and the BDS-2 satellite multipath and other issues were resolved by the BDS-3.The time transfer performance of BDS-3 PPP with different frequency combinations was studied and analyzed.Furthermore,the performance of BDS-3 PPP positioning was analyzed in terms of convergence time,positioning accuracy,and zenith troposphere delay(ZTD)accuracy.The results show that BDS-3 has the time transfer ability of sub-nanosecond accuracy,and the BDS-3 accuracy of horizontal component better than 2 cm,and the up component better than 4 cm.