Indoor localization systems are now increasingly needed in supporting location-based services (LBS). We carry out a theoretical study of an indoor positioning technique based on sequential switching. It uses available global positioning System (GPS) signals and simple deployment of so-called "GPS repeaters." The delay-lock loop (DLL) architecture of a GPS receiver has been modified into an open DLL to improve indoor positioning performance. A comparison study between simulation results using a standard GPS receiver and an improved one shows that the latter allows submetrical accuracy to be achieved.