Oscillator phase noise as a limiting factor in stand-alone GPS-indoor navigation

The field of indoor navigation has been of outstanding importance during the last few years. The low signal strength in an indoor scenario necessitates either to provide additional information to the receiver (f.ex. using GSM or WLAN) or to implement quite sophisticated algorithms which are complex or time-consuming. The task of this paper is to examine the impact of the local oscillator used within the GNSS receiver where the central figure is the oscillator´s phase noise characteristic. We briefly explain how phase noise in an oscillator can be described probably. Afterwards, we present a method to calculate the maximum feasible time of coherent acquisition which can be done in the presence of phase noise. We also show some exemplary measurement results which are to illustrate the relevance of the problem of oscillator phase noise in practice.