Multiplexing receivers to improve positioning success rate for pseudolite indoor localization

Carrier phase-based positioning such as RTK-GPS, which has centimeter-level accuracy, is ideal for mobile robot navigation. However, this technology comes with a serious problem called cycle slip, which happens when the receiver fails to track the carrier phase of signals incoming from transmitters. Cycle slip is usually caused by multipath, noise, and many other factors, and when it happens, the number of equations that can be used for position calculation decreases. As this problem arises more frequently in an indoor space, positioning success rate (PSR) tends to be lower indoors. In this paper, we introduced a method that multiplexes receivers for indoor positioning with pseudolites (ground-based GPS transmitters). With this method, positioning becomes more insusceptible to cycle slips, comparing to the use of a single receiver, because of its redundant equations for position calculation. We conducted an experiment to investigate how the number of receivers and transmitters affect PSR and positioning accuracy. The result showed that while PSR gets higher as the number of receivers increases, it does not necessarily rise with the increase of transmitter numbers. It also showed that the increase of transmitter numbers deteriorates the positioning accuracy.