Chinese area position system (CAPS) can provide positioning, time and velocity service to China region users by renting several commercial communication satellites. We studied a real-time common-view time transfer method in this paper using communication satellites of CAPS. This method can fully use CAPS resources of the communication satellites and orbit determination stations to broadcast the information of timing bias mode parameters from the ground base stations. The timing bias data information can be demodulated and calculated by users from the navigation message by receiving the satellite signal in one-way, so the common-view time transfer process are implemented. This method can provide time service with the accuracy better than 5 ns, which is a kind of high accuracy time transfer method at present. Users can obtain this kind of time services in real-time and only need to receive CAPS time service signal in one-way reception way and without the process of past-data exchange. This paper provides detailed information on the principle of the common-view time transfer method based on communication satellites. Moreover, the experiment platform has been set up to test the performance of this new method. The long baseline experimental results of Xi’an-Kashi and Xi’an-Sanya indicated that the accuracy of CAPS single-satellite is better than that of GPS single-satellite common-view time transfer. The common-view time transfer based on communication satellite can provide time service to users with the accuracy better than 5 ns.

根据北斗卫星导航系统三步走战略，北斗三号系统空中星座在2020年左右完成部署，信号的覆盖范围从亚太大部分地区扩展至全球.实际上自2018年底北斗三号系统已经可以初步提供全球服务.相应地，北斗系统的单频电离层模型从只适用于亚太大部分地区的BDSKlob模型发展到适用于全球范围的BDGIM模型.为分析北斗三号电离层模型的性能，以IGS GIM最终数据为参考，比较了2019年3月1-31日期间北斗BDGIM模型、BDSKlob模型以及GPSKlob模型在不同时段不同地区的改正效果.结果表明：北斗三号BDGIM模型在中国区域的改正率达75%以上，优于BDSKlob模型59%的改正率；在全球范围的改正率达60%，优于GPSKlob模型49%的改正率.除南半球高纬度地区外，BDGIM模型的电离层误差值均小于GPSKlob模型，其在垂直方向的电离层均方根误差值优于6TECU.