Implementation and Optimization of a Galileo E1 Two-Step Tracking Algorithm using Data/Pilot Combining and Extended Integration Time

This paper brings additional light on the previously proposed two-step tracking algorithm for E1 CBOC tracking. More specifically, assessment of the different DLL and PLL tracking loop architectures are analyzed, taking into consideration coherent and non-coherent data and pilot channel combining schemes and increasing integration time beyond data bit period, which is 4 ms for E1 CBOC signal. Our assessment is based on implementing the different tracking loop architectures in a software receiver fed with RF samples generated with a full constellation Galileo E1 simulator. The results are obtained for integration times equal and above the data bit period (i.e, from 4 to 20 ms) and for high to low C/No (i.e., from 41 down to 26 dB-Hz). Also, the influence of the secondary code removal on the tracking loops is shown using a specially conceived algorithm to acquire it. Robustness of the tracking loops is tested under low C/N0, in order to investigate the channel combining strategies. Four different combining cases are tested. Finally, performance analyses are presented and the results are discussed.