General Framework for Acquisition Performance Analysis with Application to GALILEO Signals

Abstract

Future global satellite-based navigation systems like coming Galileo and the modernized GPS will make use of ranging signals with higher chip rates and lengths of spreading PRN codes. While bringing significant improvements to the overall system performance, the utilization of such signals makes fast and reliable acquisition in the user receiver a challenging task. For each satellite signal to be acquired, an acquisition algorithm has to perform a two-dimensional search process over the uncertainty region spanned by the PRN code-phase and residual Doppler. The use of longer PRN codes leads to proportional stretching of the uncertainty region and increasing of the acquisition complexity. In order to cope with this effect the acquisition algorithms must be carefully designed using more sophisticated search techniques and taking into account features of the new ranging signals such as the presence of pilot channels and binary offset carrier modulation. This paper will address the problem of optimum signal acquisition by introducing a general framework for the performance analysis of the acquisition process consisting of three stages: detection, verification and fine acquisition. The methods used at every stage are shortly discussed and trade-offs with respect to performance and complexity of some possible acquisition options for Galileo signals are outlined.