Design And Implementation Of Positioning System Based On A-GPS

GPS tracking technology has found wide applications in recent years. However, there are obvious shortcomings of GPS, such as in urban applications, the satellite signals are vulnerable buildings, trees and other shelter, or even result in serious loss of signal. Because of the lack of GPS positioning, we proposed a auxiliary positioning system based on A-GPS(Assisted-Global Positioning System). This system mixes the GPRS and GPS together. This system achieves real-time tracking in the complicated urban traffic environment and has been proved racticality good. The main work of this thesis includes the following aspects.1. An overall design of a positioning system based on A-GPS is presented. In this thesis, through the research on the bottleneck problems, a A-GPS positioning mode is given by using pseudo-range positioning technology to determine the location of the terminal positioning. It solves the problems when the system is in the envireoments that the satellite signal is weak, the direction is complicated and the environment interfere is so great that the signal can not be locked. Positioning system framework, the location server of positioning system, the terminal subsystem of positioning system and the protocol of positioning system has been completely designed. Through the establishment of location server, it improved the sensitivity of the system and the positioning terminal time to first fix (TTFF) is effectively shortened. The functional modules of positioning terminal are highly integrated with the micro-module, which can work on bad environments. It also has small size, low power consumption, long working hours, and good concealment.2. An assisted positioning receiver is designed. The receiver system used to provide effective assistance data for the positioning to achieve assisted positioning mode. We complete the design of the receiver hardware. It includes Details of the receiver hardware, test process, the entire antenna unit into the hardware, GPS modules, MCU processing unit, GPRS modules, power modules and the main circuit board. Through test, we can see that the positioning receiver is well performed in the satellite signal reception, is stable during long time working and data transmission.3. A "multi-path effect" optimization algorithm is designed. Through the analysis of the causes of the effect and scope and the positioning system application environment, a data processing-based multipath effects optimization algorithm named transient displacement of arithmetic operations is given. It can quickly determine the true target position and control the multi-path effect in less than 12 meters. This algorithm is applied to the assisted positioning system. It can reduce the dispersion of the target location and greatly enhance the stability and reliability of the system.