2results about How to "Improve time synchronization" patented technology

The application discloses a time synchronization method based on low-orbit satellite and Beidou PPP-B2b, which comprises the following steps: 1) a central station and a client respectively acquire real-time PPP-B2b signals, pseudo distances, carrier phase observation values and broadcast ephemeris broadcast by a Beidou No. 3 satellite and low-orbit satellites through respective receivers; 2) the central station and the client respectively solve a clock difference of the central station receiver and a clock difference of the client receiver; 3) the client solves a difference value between a local time and a central station time; and 4) the time difference between the client and the central station is input into a digital frequency synthesis module of the client to adjust the clock difference of the client receiver. The application realizes real-time PPP time transmission through Beidou No. 3 precise point positioning service and low-orbit satellite positioning service, and the client can realize sub-nanosecond time synchronization without dependence on the Internet. Meanwhile, the application realizes time synchronization and communication through low-orbit satellite assistance, and enhances the time synchronization performance in interference, shielding and complex environments.

This invention discloses an algorithm for improving time synchronization accuracy in a master-slave network topology. The algorithm comprises the following steps: S1, establishing a master-slave network topology; S2, exchanging messages to obtain four timestamps and calculating the master-slave clock offset and average link delay, sending an Optimize_Req message to the master clock; S3, selecting the optimal master-slave clock offset from multiple offsets and calculating the asymmetric link delay ratio for each synchronization; S4, if the current link delay is approximately symmetrical, the master-slave clock offset is used to update the slave clock; S5, if the current link delay is asymmetric, the clock offset estimate is obtained using the maximum likelihood estimation algorithm, and an Optimize_Resp message is sent to the slave clock to update it. This invention improves the PTP time synchronization protocol by using the above algorithm, adding two message transmissions. The master clock receives the synchronization results from multiple slave clocks, further performs filtering and optimization, and then sends the updated results to the slave clocks, allowing the slave clocks to adjust themselves.