Acquisition Trade-Offs for Galileo SW Receiver

Abstract

Modernised GPS and Galileo will introduce new signal structures possessing a number of advanced features which open the room for improving acquisition and tracking performance of navigation receivers. Among these features are worth to mention the presence of pilot channels, the use of binary offset carrier (BOC) modulation and complex ranging PRN sequences formed by the combination of primary and secondary codes. Our paper will be focused on acquisition algorithms exploring signal features of future Galileo. We will consider different acquisition options and analyse their performance under various signal conditions. Following Galileo-specific acquisition options will be considered: - combining of data and pilot channels; - single sideband and double sideband, both coherent and incoherent, acquisition of BOC signals with different filtering options; - use of partial and FFT correlations We will also investigate the performance of the acquisition process as a single whole consisting of three stages: signal detection, verification and fine acquisition. Depending on what acquisition options are used on each stage, diverse acquisition schemes are possible. A few acquisition schemes will be proposed for Galileo signals and analysed. In order to obtain a general framework for defining trade-off between these schemes, the analysis will be performed from a software receiver prospective. This allows us to use the mean complexity of the whole acquisition process under given probabilities of signal detection and false alarm as a performance metric. This metric can be easily translated in the mean acquisition time, a metric widely used in literature, which is however more implementation specific. A theory framework will be introduced for the complexity analysis of the whole acquisition process and results obtained with this theory will be presented. In the conclusion of the paper, identified trade-offs for acquisition options and their combinations within different acquisition schemes will be outlined and discussed.