顾及BDS-2/BDS-3间ISB的精密定位及时频传递性能评估

Performance evaluation of precise positioning and time-frequency transfer considering ISB between BDS-2 and BDS-3

北斗卫星导航系统(BeiDou Navigation Satellite System,BDS)-3已于2020年7月31日正式向全球用户提供定位、导航和授时服务,因BDS-2与BDS-3在信号调制方式及特性上存在差异,接收机端在接收与处理BDS-2、BDS-3信号时将存在系统间偏差(inter-system bias,ISB)。文章采取忽略ISB(ISB_(NO))、ISB估计为常数(ISB_(CT))、ISB估计为随机游走(ISB_(RW))、ISB估计为白噪声(ISB_(WN))4种随机模型,分别使用GBM、WUM、CLK93实时精密产品,基于BRUX、CEDU、CUT0、HOB2、HARB、PTBB站点的观测数据,对BDS-2/BDS-3组合事后、仿实时精密单点定位(precise point positioning,PPP)及时频传递性能进行评估。结果表明:GBM、WUM产品事后平均PPP定位精度、收敛时间均在1.7 cm、23.3 min,估计ISB策略的定位及时频传递性能均稍优于忽略ISB策略,ISB_(CT)的数据处理策略最优。CLK93产品仿实时PPP的三维定位精度优于4.0 cm,估计ISB与忽略ISB的定位精度相当、收敛时间有所缩短、时频传递稳定度有所提升,ISB_(CT)、ISB_(RW)、ISB_(WN)相比ISB_(NO)解算策略在60000 s的平均频率稳定度分别提高了8.03%、25.32%、24.21%。综合比较,BDS-2/BDS-3组合PPP的ISB_(CT)、ISB_(RW)策略定位及时频传递性能优于ISB_(NO)、ISB_(WN)策略。

BeiDou Navigation Satellite System(BDS)-3 has officially provided positioning,navigation and timing services to global users on July 31,2020.Due to the differences in signal modulation modes and characteristics between BDS-2 and BDS-3,there will be inter-system bias(ISB)when the receiver receives and processes BDS-2 and BDS-3 signals.This paper adopts four random models:ignoring ISB(ISB_(NO)),ISB estimation as constant(ISB_(CT)),ISB estimation as random walk(ISB_(RW))and ISB estimation as white noise(ISB_(WN)).GBM,WUM and CLK93 real-time precision products are used respectively.Based on the observation data of BRUX,CEDU,CUT0,HOB2,HARB and PTBB,the performance of mimic real-time and post precise point positioning(PPP)and time-frequency transfer of BDS-2/BDS-3 combination was evaluated.The results show that the average PPP positioning accuracy and convergence time of GBM and WUM products are both 1.7 cm and 23.3 min.The positioning and time-frequency transfer performance of the ISB estimation strategy is slightly better than that of the ignoring ISB strategy,and the data processing strategy of ISB_(CT)is the best.The 3D positioning accuracy of mimic real-time PPP of CLK93 product is better than 4.0 cm,the positioning accuracy of ISB estimation is equivalent to that of ignoring ISB,the convergence time is shortened,and the stability of time-frequency transfer is improved.The average frequency stability of ISB_(CT),ISB_(RW)and ISB_(WN)is 8.03%,25.32%and 24.21%higher than that of ISB_(NO)solution strategy in 60000 s,respectively.By comprehensive comparison,ISB_(CT)and ISB_(RW)strategies with BDS-2/BDS-3 combined PPP have better positioning and time-frequency transfer performance than ISB_(NO)and ISB_(WN)strategies.