Data Processing And Realization Of GPS Software Receiver

GPS (Global Positioning System) can provide all-weather continuous accurate position, velocity and time information for an unlimited number of worldwide users. The GPS software receiver processes and computes GPS intermediate frequency (IF) signal in software approach with a high flexibility, which can study and realize new algorithms easily, also can be easily modified to suit the GPS signal changes, such as the changes of signal structure and intensity.This paper focused on GPS data processing and GPS software receiver implementation. Specifically as following:1. In this paper, GP2015-based GPS RF front-end chip was used for collecting GPS IF digital signal, and the IF digital signal was saved into the personal computer. Then, based on collected data, we started the research on the GPS signal acquisition, tracking, and position resolve technologies.2. In the aspect of acquisition and tracking, the basic algorithms and processes were introduced. Because weak GPS signal is difficult to be acquired, a new acquisition algorithm for weak GPS signal was proposed. After the simulation experiment of GPS weak signal acquisition, the new algorithm improved the receiver performance of weak GPS signal acquisition.3. During the ephemeris demodulation and position resolving, we began from the tracking results, and then sub-frame synchronization, parity checking, navigation message extraction and the satellite and user position calculation. The GPS position experimental results proved that the implementation of GPS software receiver was successful. A new ephemeris prediction method--the use of outdated satellite ephemeris was proposed, which can position rough without the latest ephemeris. This method can shorten the time to first fix (TTFT), even in the situation that receiver can't track satellite successfully.4. About software receiver architecture and interface design, the basic hardware and software receiver architecture was described, we improved the conventional software receiver structure in the software process with closed-loop design. Interface design used Qt Designer under Linux operating system, the positioning results were shown with the graphical interface. Interface and running modules were separated, which made the configuration of GPS software receiver more flexible.In brief, this paper studied the key technologies for GPS software receiverm, such as GPS signal processing, positioning solver. The software architecture of GPS software receiver had been improved and then realized. Through the GPS experiment, the feasibility of the program was demonstrated.