Enhanced bayesian detection for weak GPS and Galileo signal acquisition

The acquisition of any Global Navigation Satellite System (GNSS) signal is one of the most important receiver operation. A receiver must be able to identify which satellites are in view as fast as possible in order to reduce the Time To First Fix (TTFF). Moreover, the acquisition must be performed even in weak signal power situation which increase the challenge of this specific receiver function. The acquisition procedure can be split into two main specific functions: the Search Space (SS) evaluation and the signal detection. Different ways of obtaining the SS have been proposed so far as well as solutions to the problem of signal detection, although in literature more time has been devoted to the first problem. In this paper the attention will be focused intensively on the problem of the signal detection, or in other words to the methodology with which a signal coming from a specific satellite is declared present or absent. This paper will investigate a different detection approach not based on the Neyman-Pearson criterion and it will be validated both by means of computer simulations and by using real collected GPS data. The paper will show how the proposed methodology can be successfully employed for the GNSS signal acquisition and how it can be used as an alternative of the coherent and non-coherent extension of the integration time for the detection of weak signals when a collection of measurements is available. The method presented in this paper presents several advantages in terms of robustness and, despite of the difficult mathematical background, its implementation results to be quite straightforward.