Research Of Theoretical Modeling And Application On Clock Synchronization In Distributed Simulation System

The importance of maritime security is becoming more and more important.It is increasingly recognized by people that maritime search and rescue is becoming a part of modern security planning.As a major aspect of the planning,how to make the training of the maritime search and rescue scientificly effectively should be paid more attention.In this context,we developed a simulation system for maritime search and rescue.The simulation system of maritime search and rescue is including command centers,search and rescue vessels,search and rescue aircraft,and accident scene etc,and it is a typically distributed system.Search process need strict clock synchronization,and the reasons are as follwos.The lack of clock synchronization may affect the accuracy of search and rescue,reduce the coordination of search and rescue process and even cause disastrous consequences as the failure of search and rescue.Therefore,the clock synchronization has been placed in a very important position in the development of simulation system for search and rescue,and clock synchronization is the focus of this paper.In order to realize clock synchronization,firstly,we establish a mathematical model.Concidering of the actual search process contains certain contingencies which can't guarantee that the subsystem can keep in touch with the clock sever,we established two mathematical models.One has the stability of clock-base,and the other doesn't has the stability of clock-base.When we could get in touch with the clock,we use the one has the stability of clock-base,and when we couldn't get in touch wity the clock,we use the other one.With careful analysis of the actual situation and reference of the mathematical model,we developed a system clock synchronization program.In the external synchronization we use GPS to adjustment time of the clock serve in order to have a reliable clock-base.In the interior synchronization,we established two functional modules.Using the operating system services W32Time and Winsock network programming interface,we realize the clock synchronization of the system.Through simulation tests,basically,the clock synchronization system can meet the needs of practical application.