Characterization and Validation of GNSS Multipath-Induced Doppler Measurement Error

Global Navigation Satellite System (GNSS) receivers operating in urban environments frequently encounter multipath interference, a phenomenon wherein direct and reflected signals interact. The Doppler frequency estimation by the GNSS receiver holds critical significance for precise signal synchronization and plays a pivotal role in user velocity estimation. However, a notable research gap exists concerning the multipath effects on the receiver frequency-locked loop (FLL). Therefore, this paper provides a quantitative characterization of the receiver Doppler frequency measurement error in urban areas. A realistic receiver FLL simulator, integrating the ray-tracing at the base-band signal processing level, is introduced to simulate the continuous feedback tracking performance under multipath interference. Real experiments are conducted in urban areas for the validation of theoretical findings and the simulator's reliability. An 81% simulation similarity can be attained. Consequently, the Doppler frequency and velocity measurement errors are quantified by considering factors such as the signal ray parameters, tracking loop architecture, and user dynamics.