Research And Design Of Clock Synchronization Technology In Wireless Network

Wireless network is highly flexible,easy to install,easy to expand,and supports mobile computing.With the rapid development of network communications and computer technology,wireless network is widely used in military communications,smart homes,environmental monitoring,medical care,intelligent transportation,etc.As one of the key issues in the research of wireless network,clock synchronization is the basis for completing multiple functions such as power management,multiple accesses,cooperative sensing,synchronous frequency hopping,and data aggregation.Therefore,research on clock synchronization technology in wireless networks has important theoretical significance and practical value.A novel clock synchronization technology is proposed for wireless network under the framework of AS6802 standard.The content of the work is listed as follows:1)The process of clock synchronization technology is divided into two parts: the clock tracking phase and the clock compensation phase.The clock tracking phase is consisted of monitoring process and a locking process.2)The monitoring process of the clock tracking phase can achieve dynamic measurement of transmission delay parameters and real-time monitoring of network nodes through the transmission of synchronization messages,which can provide the latest transmission delay and number of network nodes for subsequent locking processes.3)The locking process in the clock tracking phase calculates the deviation of the local clock through the transmission of synchronization messages,provides clock compensation parameters for subsequent clock compensation phases.The locking process uses deterministic schedules for data communication to ensure the certainty and reliability of synchronous message transmission.4)In the clock compensation phase,the frequency drift of the local clock has the characteristics of continuous time variation.This thesis proposes a clock compensation method based on locally weighted linear regression to improve the accuracy of clock synchronization.The linear regression process based on the least square method is susceptible to outliers.This thesis proposes a robust regression clock compensation method based on least trmmed squares estimation to improve the robustness of clock synchronization.Finally,a joint simulation platform based on OPNET and MATLAB is set up in this thesis to verify the clock synchronization technology solution.It proves that the solution can achieve a synchronization accuracy of 5μs through the clock compensation method of local weighted linear regression.At the same time,the solution effectively improves the ability of the clock compensation process to resist outliers through the clock compensation method of robust regression.When the proportion of outliers less than 50%,the clock synchronization error of this solution is reduced by up to 67% comparing with the non-robust regression clock compensation method.In summary,the clock synchronization technology solution proposed in this thesis meets the requirements of clock synchronization in wireless network and has certain application value.