| With a wider variety of real-time scenario springing up,the demand for high-precise time has become increasingly prominent among the fields of Internet of Things,Internet of Vehicles and Industrial Internet.Therefore,timing technology,which can be used to solve the problem of time synchronization,obtains of great concern in the industry.Traditional timing method relies on the radio signal from the Global Positioning System,which degrades greatly in the non-line of sight propagation environment,thus difficult to meet the needs of the increasingly complex scenario.Telecommunication network features a wide coverage range,and its signal propagation is less vulnerable to the multi-block buildings and indoor scene compared to the satellite signal.Hence,timing through telecommunication network is an effective complement for global navigation satellite system timing method.The current research of telecommunication network time synchronization lays more attention to the fixed network equipment time synchronization,which enables telecommunication network to transmit high-precision time information.However,the insufficient research still exists on mobile network time synchronization and related protocol standards,which makes the application of mobile network time synchronization very hard to spread.According to the fact,a design and implement of timing gateway based on mobile network time synchronization is necessary,as an exploratory study for the applicability of mobile network time synchronization.The main research contents and work are as followed.The thesis completes the design of timing gateway based on mobile network time synchronization.It first analyzes the function requirements of the timing gateway,and designs the system architecture based on the analysis,including hardware and software architecture.Then the thesis gives detailed functional module designs of guard time interval for the gateway,time synchronization and timing service for terminals.It designs a scheme of time synchronization method based on Time Advance adjustment,which is provided by the mobile network protocol,to deal with the problem of inaccurate timestamp from the application layer.The thesis also designs the management solution to the different timing precision and access methods including WiFi and Bluetooth,to solve the problem of diverse terminal access methods and time service requirement.The thesis completes the implement and test of timing gateway based on mobile network time synchronization.It implements the design scheme based on STM32 hardware environment,including the functional module of guard time interval by 32.768kHz crystal oscillator,the functional module of time synchronization by Network Time Protocol,and the functional module of timing service for different terminals using ESP8266 and ATK-BLE01.Additionally,the thesis builds a separate test environment based on a set of Universal Software Radio Peripheral and the system environment of srsRAN.The thesis designs a contrast test scheme for the theoretical performance of timing gateway based on Precision Time Protocol,and test the capability of time synchronization scheme on the basis of these. |
