N-Gene GNSS software receiver for acquisition and tracking algorithms validation

N-Gene is a GNSS receiver completely designed in software, able to run in real-time on a common Personal Computer. This kind of receiver implements the concept of Software Defined Radio (SDR) and can be used as a test-bed for the development of innovative algorithms and for their validation in a real-time environment. This paper presents the solutions adopted for the signal acquisition and tracking tested on N-Gene. The acquisition algorithm is a variant of the classical “fast acquisition algorithm” where the signal correlation is obtained in time domain by means of two Fast Fourier Transforms (FFTs) and a single Inverse Fast Fourier Transform (IFFT). A solution for improving the tracking performance in case of low C/N₀, is also proposed. The work on the signal tracking focuses on a robust normalization of the discrimination functions within the tracking loops. The algorithms are presented highlighting the advantages in terms of computational complexity, robustness and performance.