GPS L5 signal acquisition exploiting Neuman-Hoffman code transitions

This paper proposes a new strategy for the acquisition of the GPS L5 signal. Although the L5 signal is mainly thought for aircraft navigation, it also will serve as a robust third signal for a broad range of GPS civil users. The GPS L5 signal features an enhanced signal structure, with two components, one with and one without a navigation message. The new algorithm identifies Neumann-Hofmann code transitions on the pilot channel to rapidly synchronize the secondary code. The paper demonstrates that the search of the Neumann-Hoffman code phase corresponds to the search of a leaf node in a tree-data structure. The basic idea behind the algorithm is to take advantage of sign transitions and detect distortions of the Cross Ambiguity Function (CAF). The algorithm is based on the Fast Fourier Transform (FFT) in time domain, but it reduces the complexity of some acquisition algorithms proposed in the past, as it does not use zero padding techniques. The algorithm is able to estimate the code phase offset and the Doppler frequency with a reduced number of FFTs, therefore it is a suitable solution for software radio receivers.