Characterizing Different Open Loop Fine Frequency Estimation Methods for GNSS Receivers

The acquisition stage of any Global Navigation Satellite System (GNSS) receiver is responsible to coarsely estimate the code delay and Doppler from the received signals of all the visible satellites. From computational point of view during the acquisition stage the right strategy is to find the signal with as coarse frequency grid as possible in order to accelerate the search. After the coarse estimation has been performed, an additional frequency refinement could be possible for tracking loops which is equivalent to frequency offset estimation. In urban and moderate indoor applications closed loop schemes like Frequency Lock Loop (FLL) exhibit loss of lock behavior. In this paper, in order to avoid this behavior, we propose and characterize some alternatives for fine frequency offset estimation based on some classical techniques which can be considered as open loop schemes for fine frequency estimation.