Investigating Indoor Gps Doppler And Pseudorange Characteristics

Global Navigation Satellite System (GNSS) receivers suffer significant degradation in indoor environments due to the effects of multipath and attenuation. Signal attenuation of up to 30 dB caused by loss of signal strength through a propagation medium makes signal detection more difficult and increase the variance of parameter estimation. Multipath reflections cause two problems; signal fading and considerable measurements errors in indoor locations. In this study, the accuracies of indoor GPS observations, namely pseudorange and Doppler measurements, are investigated in order to characterize the effect of noise and multipath on these measurements. Applying an A-GPS method and extending the coherent integration time up to hundreds of ms enable the receivers to acquire GPS signal indoors. Two DGPS strategies have been considered. The first DGPS measured the noise only effect and the second DGPS measured the integrated effect of noise and multipath. Comparing the measurements extracted from the two DGPS approaches, a good insight into the separate effect of noise and multipath is provided. Different metrics are analyzed, namely Delay profile, Power Spectral Density (PSD) and differential pseudorange and Doppler measurement precision.