3D building model-assisted multipath signal parameter estimation

Multipath remains a dominant source of error in satellite-based navigation, despite a great deal of effort by researchers and receiver manufacturers to reduce it. Mitigation of multipath errors is especially difficult when the Doppler shift between the direct and secondary propagation paths is very small (approximately 1-2 Hz) and this is usually the case in urban canyons where the reflectors are almost parallel to the direction of motion of the receiver. Multipath parameter estimation is one option; however, the method needs the number of secondary paths in order to estimate the multipath parameters. Moreover, in weak signal environments, the problem becomes more challenging. In this paper we present multipath parameter estimation assisted with a 3D building model to provide the number of secondary paths as well as initial estimates for the relevant delays. The estimation is based on a Least Squares estimation technique using a grid of correlators. The concept is proven using simulated data and tested using real data. Result shows that the accuracy of estimated parameters improves significantly if the estimator is aided with 3D building model information.