Research Of Real Time GNSS Software Receiver Based On USRP

With the rapid development of the global satellite navigation system,its application in various fields has become more and more widespread,and it has attracted worldwide attention.As the user equipment of navigation system,the GNSS receiver is an important carrier to realize navigation and positioning functions,and is the basis of a navigation system to provide other services.However,the hardware receiver,which is relatively fixed in design,can't adapt the current rapid development of the satellite navigation in signal processing algorithm,and can't keep up the needs of users.But the software defined reciver is paid attention to because of its good versatility,flexibility,easy to carry on the updating and the algorithm verification,which has made up the shortcoming of the hardware receiver.After analyzing and comparing the advantages and disadvantages of the traditional hardware receiver and software defined receiver in detail,this paper introduce the development of the software recivers in recent years,the development of the software defined radio platform and the development environment.The on the base of these,the direction and key point of this dissertation are proposed,and the main research content and the basic structure of this dissertation are determined.Taking the GPS L1 signal and Beidou navigation system B1 signal for example,this paper analyse the composition,characteristics and modulation methods of the navigation satellite signas,studies the general structure of the software receiver,and base on these above,the design of the software receiver in this paper is proposed.Research on the baseband signal processing part of the software receiver,and verify by conducting experiments.This part mainly includes two modules: acquisition and tracking,then study the principle and algorithm respectively.Three acquisition algorithms are introduced,which are serial acquisition,parallel frequency acquisition and parallel code phase acquisition,as well as carrier phase locked loop,carrier frequency locked loop,code ring and complete signal tracking loop are introduced.Based on these all above,the actual acquisition and tracking algorithm flow is designed and verified by experiments.Research on the navigation solution part of the software receiver,which is divided into three parts: the navigation message extraction and decoding,the calculation of satellite position and the navigation system positioning solution.In the part of the navigation message extraction and decoding,this paper studies on the bit synchronization,frame synchronization and the verification methods of the navigation signal,and verified by experiments.In the part of the navigation system positioning solution,this paper studies on the bacic principle of the navigation positioning solution,the solving methods of the position equation,and the positioning solution based on Kalman Filtering.Then design the positioning solution algorithm flow,and verified by experiment.Finally,based on GNSS-SDR,an open source software,and USRP software radio development platform,complete the development of each algorithms of the Beidou Navigation System software receiver,then through the experiments,verify the function and performance of the softeare receiver,real-time positioning calculation can be carried out.