| As one of the products of GNSS augmentation technology,Ground Based Augmentation System(GBAS)can provide centimeter-level precision positioning service,and greatly improve the navigation performance of satellite navigation system.Its broad market application prospect makes researching independently data processing platform of GBAS especially NRTK become the key technology of universities and research institutes.One of the essential steps in the process of studying these key technologies is to verify their function and performance.However,the commonly used post-authentication method cannot be used to test the network transmission function of GBAS data processing platform.At the same time,online real-time verification method exists the following problem:real-time data flow is not shared and the cost of building base station is high;there exists the shortcomings of great influence of the testing environment and the reproducibility of experimental results is poor;at the same time,the experiment process is time-consuming.Then,this paper designed and achieved a distributed GBAS simulation verification platform according to system simulation theory,network programming principles and multithreading development model,which can be used to complete GBAS data processing key Technical verification work with a number of computers in the case of not needing a lot of field work.The platform solves the problems existing in the traditional online verification method with the advantages of nondestructive,repeatability,reliability,security and economy.It provides a realistic and reliable simulation environment for the verification of GBAS data processing key technology.The main contents of this thesis are as follows.(1)We designed and developed the distributed GBAS simulation verification platform.According to the similarity modeling principle and combining with composition and working principle of GBAS,we put forward the technical scheme of the simulation platform.Subsequently,we determined the structure and function of the system and elaborated the development process of GBAS simulation verification platform.(2)We focused on the key technologies of time management of GBAS system simulation,which including time synchronization and time advance control.Above all,during the process of research on time synchronization,we developed the time synchronization software of high precision based on data filtering algorithm and CPU time stamp,which greatly improves the stability and precision of the conventional time synchronization method.It can satisfy the millisecond precision of the time synchronization requirements.(3)We researched on the time advance strategy.Based on the conservative time promotion strategy,we proposed a user controllable time advance strategy,which established the simulation model of simulation time and system time,which can accelerate the simulation task according to the user’s needs without affecting the simulation results to improve the efficiency of verification experiment.We verified that the adaptive time promotion strategy did not appear deadlock phenomenon.We analyzed the reason of the time promotion strategy by the example simulation,which shows that the GBAS simulation platform has real-time and super real-time simulation capabilities.(4)Based on the Virtual Environment principle of system simulation technology,we put forward the simulation of the actual experimental environment fault.We systematically analyzed several environmental failures that can often affect the function and performance of GBAS data processing platform,and simulated these environmental faults by simulation technology.This makes the GBAS simulation verification platform become closer to the actual system of verification environment,and increases factuality and credibility of the simulation platform. |
