Differential Post Detection Integration Techniques for Robust Code Acquisition

In this paper, the problem of code acquisition for spread-spectrum systems is investigated in the presence of frequency errors. The classic approach of noncoherent post detection integration (NCPDI) is contrasted with differential post detection integration (DPDI), presented in two different versions, namely DPDI-Real and DPDI-Abs, respectively, suited for fine and large frequency offsets. The differential schemes are characterized thoroughly introducing a novel analytical treatment that is validated by simulations. In order to fairly quantify the potential gains introduced by the differential solutions, specific detector parameter optimization is performed for each scheme. The interesting result is that the DPDI significantly outperforms the classic NCPDI approach for large frequency errors, and behaves close to it for small offsets. DPDI can, thus, be considered as a very robust PDI solution with moderate complexity.