Fast Iterative Maximum-Likelihood Algorithm (FIMLA) for Multipath Mitigation in Next Generation of GNSS Receivers

In this paper, we efficiently solve the maximum-likelihood (ML) time-delay estimation problem for GNSS signals in a multipath environment. Exploiting the GNSS signal model structure and the spreading code periodicity, we develop an efficient implementation of the Newton iterative likelihood-maximization method by finding simple analytical expressions for the first and second derivatives of the likelihood function. The proposed Fast Iterative ML Algorithm (FIMLA) for time-delay estimation is shown to be an attractive technique for mi-tigation of closely-spaced multipath for current GPS receivers as well as future modernized GPS and the European Galileo systems based on BOC signals. Simulation results show that FIMLA improves the performance of the ML synchronization algorithm in presence of multipath. 1