Performance Evaluation of VDFLL Architecture for a Dual Constellation L1/E1 GNSS Receiver in Challenging Environments

In urban environments, standalone GNSS receivers can be strongly affected to the point of not being able to provide a position accuracy suitable for use in vehicular applications. In this paper, a vector delay/frequency-locked loop (VDFLL) architecture for a dual constellation L1/E1 GPS/Galileo receiver is proposed. In the proposed vectorized architecture, the individual DLLs and FLLs of each tracked satellite are replaced with an Extended Kalman filter (EKF), responsible for both estimating the user’s position, velocity and clock bias and closing the code/carrier updates for each GPS L1 and Galileo E1 tracking channels. In this work, a detailed performance comparison between the scalar tracking and VDFLL configuration is assessed under multipath conditions that are generated by the DLR urban multipath channel model. Contrary to the conventional tracking, the L1/E1 VDFLL loop is able to accurately pursue the frequency and codedelay estimation without the requirement of signal reacquisition process and within limited positioning error.