Composite GNSS signal acquisition in presence of data sign transition

Abstract

In this paper, the problem of acquiring new composite Global Navigation Satellite System (GNSS) signals of the next generation systems (such as Galileo and GPS modernization) is addressed and analyzed, focusing on the problem of sign reversal transition due to the navigation data message in the data channel and to the secondary code in the pilot channel. Moreover, the sign transition present on the block of samples being processed produces a Cross Ambiguity Function (CAF) peak splitting along the Doppler shift axis of the search space matrix constructed during the acquisition stage and it may lead to a wrong Doppler shift estimate. A new two steps acquisition method has been proposed in order to cope with the CAF peak impairments. Due to the availability of data and pilot components separately broadcast in the new composite GNSS signals, in order to overcome the power loss problem and also to mitigate the CAF peak splitting impairments, novel non-coherent channels combining, differentially coherent channels combining and coherent channels combining techniques based on the two steps acquisition scheme have been proposed for jointly combining data and pilot components to recover all the transmitted power from both channels. These proposed techniques have been deeply characterized from a statistical point of view. Monte Carlo simulation results performed on the simulated Galileo E1 Open Service (OS) signals have revealed that these developed techniques provide much improved acquisition performance and enhanced acquisition sensitivity in comparison to the state of the art acquisition techniques.