Signal-in-space accuracy for BeiDou navigation satellite system:Challenges and solutions

<正>Service accuracy of global navigation satellite system(GNSS)is determined by satellite constellation,signal-in-space(SIS)accuracy and signal transmission errors.The State Council Information Office of the People’s Republic of China issued China’s BeiDou Navigation Satellite System(BDS)White Paper(www.beidou.gov.cn/fbh2016.html)on Jun.16th 2016,which notes that,BDS takes a three-step development strategy,from domestic service,through Asia-Pacific regional service,to global service,and features mixed constellation of Geostationary Earth Orbit(GEO),Inclined Geostationary Earth Orbit(IGSO)and Medium