The Resarch On The Time Management And Advancing Strategy In GNSS Simulation System

Global navigation satellite system(GNSS) is a typical distributed system, The application of the GNSS simulation system is facing a huge challenge.For example,it usually needs a high reliability requirement and a large amount of date exchange.As a distributed system,it is also wide and complex.So the advanced technology of distributed simulation must be used in the GNSS simulation system. High level architecture(HLA) is a new generation of distributed interactive simulation(DIS).Its purpose is to provide a common framework for various types of simulation system. The interoperability and reusability of the DIS system can be improved effectively with the HLA technology. The time management service is an important part of the HLA specification, its main purpose is to ensure the logical correctness of distributed simulation. The performance of simulation system can be improved if a effective time management strategy was used.The main contents of this thesis can be summarized as the following four points:1) According to the design method of the Federation Development and Execute Process Model(FEDEP) and the requirement of the GNSS simulation system, The federation was designed for the eight federal members,namely the federal control member、Satellite member、Monitoring station、Master station 、Injection station、user station、system evaluation and visualization of members. The SOM and the simulation flow of the each federal members was designed.2) The synchronization problem of the GNSS simulation system was analyzed.We designed three synchronization points,which were inserted in the different stages of the simulation.In order to simplify the simulation of clock characteristics of each members,a method using synchronization point label was designed.3) The time management strategy of each federate was designed with the HLA time management service. We also discussed how to determine the message order and the time lookahead.The HLA puts forward two time advancing method,namely the conserved and optimistic method. The time advancing method of the GNSS simulation system use the way of the time steps.Finally,we analyses the time advancing flow of the system in one step using the GALT algorithm.4) The GNSS simulation program use the BH RTI 2.3 as the development platform of HLA. Complete the GNSS simulation system which was designed in this paper and verify its correctness.