The high-precision time and frequency transfer method, based on the global navigation satellite system (GNSS) precise point positioning (PPP), has high precision, wide range, and low cost, and the GNSS common-view (CV) can remove all satellite clock errors and partial satellite orbit errors. We conducted a study to select the best satellite and combined PPP and CV to eliminate satellite clock errors, weaken the impact of satellite orbit errors, and unmodeled atmospheric asymmetry in PPP frequency transfer, thus improving the performance of frequency transfer. This study uses conventional dual-frequency ionosphere-free PPP that does not solve for an azimuthal asymmetry in the troposphere. It uses international GNSS service (IGS) products to determine the carrier phase difference between each CV satellite time and the ground clock, for each epoch. Then, the comparison difference is obtained by directly subtracting the carrier phase differences between the CV satellite time and two ground clocks. For each hour, only the satellite that is fully visible at both sites and gives the smallest standard deviation in time comparison of the day between the two ground clocks is selected as the CV satellite. To evaluate the performance of PPP-CV, five stations connected to individual active hydrogen masers are selected to form four links, of which two stations (USN7 and USN8) are common-clock and common-antenna. The results show that the time comparison precision of PPP-CV improves by approximately 12% on average for the three European links compared to PPP with respect to IGS final clock products. For frequency transfer modified Allan deviation (MDEV) over 600,000 s, PPP-CV can reach 2 × 10^–16 and 2 × 10^–17 for the SPT0-IENG and USN7-USN8 links, respectively. In addition, the frequency transfer stability ranging from 1200 s to 60,000 s of PPP-CV improves by 7% on average compared to PPP, and its short-term stability is also better than that of PPP when the CV satellite does not change. However, the performance of PPP-CV is comparable to PPP when the link length reaches 5991 km and the short-term stability of PPP-CV is slightly worse than PPP when the CV satellite is constantly changing.

基于全球导航卫星系统（GNSS）精密单点定位（PPP）的高精度时频传递方法，精度高、范围广、成本低，并且GNSS共视（CV）可以消除所有干扰。卫星时钟误差和部分卫星轨道误差。我们进行了选择最佳卫星的研究，将PPP和CV相结合，消除卫星时钟误差，削弱PPP频率传输中卫星轨道误差和未建模的大气不对称性的影响，从而提高频率传输的性能。本研究使用传统的双频无电离层 PPP，无法解决对流层中的方位角不对称问题。它使用国际 GNSS 服务 (IGS) 产品来确定每个历元的每个 CV 卫星时间与地面时钟之间的载波相位差。然后直接减去CV卫星时间与两个地面时钟之间的载波相位差即可得到比较差。对于每个小时，只有在两个站点都完全可见并且在两个地面时钟之间的当天时间比较中给出最小标准偏差的卫星被选择作为CV卫星。为了评估PPP-CV的性能，选择连接到各个有源氢脉泽的五个站形成四个链路，其中两个站（USN7和USN8）是共时钟和共天线的。结果表明，对于IGS最终时钟产品，PPP-CV的时间比较精度在欧洲三个链路上比PPP平均提高了约12%。对于超过 600,000 秒的频率传输修正阿伦偏差 (MDEV)， SPT0-IENG 和 USN7-USN8 链路的PPP-CV 可以分别达到 2 × 10 ^–16和 2 × 10 ^{–17 。}此外，PPP-CV在1200~60000s范围内的频率传输稳定性比PPP平均提高了7%，并且在CV卫星不发生变化的情况下，其短期稳定性也优于PPP。然而，当链路长度达到5991 km时，PPP-CV的性能与PPP相当，而当CV卫星不断变化时，PPP-CV的短期稳定性略差于PPP。