SOFTWARE-BASED GPS RECEIVERA RESEARCH AND SIMULATION TOOL FOR GLOBAL NAVIGATIONSATELLITE SYSTEM

摘要

Global Navigation Satellite Systems (GNSS) have been used for the past 20-30 yearsrnsuccessfully both in civil and military community. Transit, GPS and GLONASS are examples ofrnGNSS. GPS has already proved it's availability and reliability for many applications. In nearrnfuture, new GNSS called Galileo, will be launched by Europe. However, the receivers for allrnthese systems are built using application specific integrated circuits (ASICs), which we oftenrncall hardware GPS receiver. A user has the least level of flexibility in setting or implementingrnthe parameters in this type of receiver. Especially, the level of flexibility is limited for thernresearchers and developers to implement their own algorithms. Software-based GPS Receiverrn(SGR) helps us processing the GPS signal at the lowest level of GPS raw signal data from thernantenna. A SGR consists of a front-end device that converts the radio frequency signal from thernantenna to an intermediate frequency in digital format. The signal thus converted is processed byrnhigh level programming language to compute position and velocity. In SGR, it is possible to dornacquisition and tracking using different parameters and threshold values, which give a user totalrnflexibility of operation. This helps in processing weak signal, multipath mitigation and simulatern“what-if” scenarios. In this paper, we will discuss about software-based GPS receiver and showrnhow it can be used for research and simulation in the field of Global Navigation Satellite System.