Improved pseudolite navigation using C/N0 measurements

The problem of indoor navigation using pseudolites is investigated and two different approaches, employing synchronous and asynchronous technologies, are considered. It is shown that synchronous pseudolite systems, commonly considered more accurate, seem to be unsuitable for deep indoor operations: in complex propagation environments, the synchronization required for metre level navigation is difficult to achieve and a different solution should be adopted. The potential of asynchronous pseudolite systems is demonstrated and indoor navigation with metre level accuracy is obtained using C/N0 measurements. In particular, the spectral characteristics of C/N0 measurements are investigated and used to design a pre-filtering stage which, in turn, is employed to remove high-frequency noise. Pre-filtering significantly improves the navigation performance in harsh indoor environments.