Analysis of GNSS Signal Correlation in Terrestrial Vehicles

The purpose of this paper is to analyze the reaction of a real-time hardware multicorrelator GNSS receiver in realistic environments. In particular, we investigate how the GNSS signal correlations are distorted in two vehicular scenarios. The scenarios were recorded with a multi-frequency bit grabber and playback in the laboratory. The test campaigns were performed driving in two contrasting propagation environments. Rotterdam downtown was chosen to assess the multipath in challenging urban conditions while Nieuw-Vennep was selected as an open-sky/rural environment. The objective is to characterize the multipath of the received signal using a high-end GNSS receiver able to store 41 correlator outputs. The multipath error is estimated by comparing a local reference of the correlation function, which is estimated by using a GNSS simulator in the absence of GNSS disturbances, to the correlations estimated by the GNSS receiver in the vehicular scenarios. Two methods are considered. The first one consists in computing the error between the reference correlation function and the estimated ones. We evaluate the impact of the multipath on the temporal domain. The second one is based on estimating the multipath by implementing a Non-linear Least Squares estimator. The estimator provides reliable information about the power of the direct and reflected signals. We analyze the differences and similarities between both scenarios for several satellites having different elevations.