Study On Position Data Processing And Application Layer Protocol Design Of Vehicle Navigation Terminal

The extensive popularization of vehicle has brought great convenience to people'swork and life, but it also has initiated a series of questions. The sharp increase of thetraffic flow has made the bottleneck of the traffic route. Traffic jam, road block and trafficaccident frequently happen. Moreover, the complicated traffic network makes people at aloss as to what to do. The traffic jam that frequently takes place makes people difficult tochoose the correct running route. People are difficult to know the surrounding traffic andthe position of themselves when they are in a strange geographical environment. Peopleare difficult to get the service needed nearby as they don't know the distribution of theservice facilities around while needing the service. People may face the danger of gettinglost when they are in fieldwork. It is an important research about how to furthest improvetraffic flow with the limited limited road traffic facilities, and then the intelligent trafficsystem (ITS) comes forth.ITS is a function omni-directionally, real-time, accurate and high-efficientcomprehensive traffic transportation administrative system, which integrates theinformation technology, transmission technology of data communication, electronicsensing technology electronic control technology and computer treatment technology, etc.The vehicle navigation system is an important basic branch of ITS. It is in terms of drivermainly, and especially solves the problems of the optimum path planning andnavigatation.The vehicle navigation system can mainly be classified into two kinds, one isindependent navigation system and the other is centre-decided navigation system. Inindependent navigation system, the functions of position and path-planning are allrealized in the vehicle terminal, and in central-decided navigation system, some functions(such as path-planning and navigation map) must be realized through the communicationnetwork. Compared to independent navigation system, in central-decided navigationsystem, the vehicle terminal requires low hardware and its cost is low. Central-decidednavigation system also has some other advantages, it is easy to provide added service,and the path-planning is easy to add dynamic traffic information. Due to these advantages,central-decided navigation system has broad application prospects in the popularizationcourse of the vehicle navigation system. Moreover, the central-decided navigation systemis suitable for transportation trade, as it is very apt to realize fleet management.This paper analyses the system structure of the central-decided navigation system,and then mainly studies on GPS position data processing and designs the GPRS-basedapplication layer protocol between vehicle terminal and control center. This paper alsomakes up the software system of vehicle terminal. The main research contents are asfollows:1.The system structure of the central-decided navigation system and the functiondemands are analysed in this paper. It is very important to analyse the system structure ofcentral-decided navigation system and its function demands, as they are importantindexes to examine the project. This paper gives the system structure of the vehicleterminal and the functiuon structure of the control center, especially the software systemstructure of the vehicle terminal. This paper proposes a kind of vehicle terminal softwareplatform which is simple and effective. The platform is composed of interface layer,device layer, console layer and task layer. The interface layer provided datacommunication between MCU and outside devices. Device layer has several devicethreads, each manage one device, such as initialization, drives and functional opration ofthe device. Console layer only has one thread, which processes data coming from devicelayer and manages relevant task threads of task layer. Task alyer also has several threads,each realizes one function. Per layer of the platform is clear and the function is single.Several devices and several tasks can run at the same time in this platform of the vehicleterminal. The structure of the platform is clear and it is easy to delete or add devices ortasks on the platform.2.The GPS position data processing of the vehicle terminal is studied in thispaper.The GPS position data processing is an essential technology of the vehicle terminal.The processing quality directly affects the performance of the navigation. As thecentral-decided vehicle navigation system has the monitoring function, the vehicleterminal need pass on massive GPS position data, therefore, the research of position datacompression algorithm is very significative. This paper proposes an effective datacompress algorithm based on the historical data redundance which has a big compressionratio and is very simple. Before the map match and the path guidance, the GPS positiondata must be transformed under the coordinate system which corresponds for thenavigation electron map. In order to enhance the precision of the position data, it isnecessary to research the filter processing of the GPS position data. This paper does somereseach about the coordinate transformation and the filter processing of the position data.This paper also does some experiments to confirm the algorithms of the coordinatetransformation and filter processing.3.The network communication between the vehicle terminal and the control center isstudied in this paper. The communication between the vehicle terminal and the controlcenter is an essential technology to the central-decided vehicle navigation system. Thereliability of the communication influences the performance of the system derectly. Thispaper chooses the GPRS network as the public mobile communication platform, thenanalyses the structure of the network communication between the vehicle terminal andthe control center, and then designs the application layer protocol, in which the protocolsof user login, passing on position data and downloading navigation data are introduced indetail.4.The software design of the vehicle terminal is researched in this paper. This paperprovides a software system structure of vehicle terminal when researching the systemstructure of the central-decided vehicle navigation system. And then this paper relizes thesoftware system platform, includeing the interface layer, the device layer , the consolelayer and several functions of the task layer, such as dialling and answering the call,sending and receiving SMS.Although this paper has studied on some problems and some key technologies in thecentral-decided vehicle navigation system, it's far from enough and there are still manyproblems which are requested deeple research and solution. The control center has notbeen built, and the vehicle terminal needs to perfect. However, due to the widespreadapplication prospect of the central-deicded vehicle navigation system, the theory and thepractice research in this paper will be contributed to the future work.