SUBMITTED TO T-COM IEEE, VOL. XX, NO. XX, JANUARY 2005 1 Differential Post Detection Integration Techniques for Robust Code Acquisition Marco Villanti, Paola Salmi, and Giovanni Emanuele Corazza Abstract In this paper, the problem of code acquisition for spread spectrum systems is investigated in the presence of frequency errors. The classic approach of non coherent 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 which is validated by simulations. In order to fairly quantify the potential gains introduced by the differential solutions, specific detector parameters optimization is performed for each scheme. The interesting result is that DPDI significantly outperforms the classic NCPDI approach for large frequency errors, and behaves close to it for small offsets. DPDI can be thus considered as a very robust PDI solution with moderate complexity. Index Terms Code acquisition, frequency error, post detection integration, differential techniques, spread spectrum systems I. I NTRODUCTION In recent years, spread spectrum technologies have found extensive commercial exploitation in both communication systems, such as 2G and 3G cellular networks, and navigation systems, as the operational GPS and the up-coming GALILEO systems. The most distinctive feature of spread spectrum transmission is that the signal power spectral density is very low, typically under the noise level, N 0 , and in these harsh conditions the initial recovery of the received spreading sequence epoch, identified as code syn- chronization, becomes one of the most critical design issues. Indeed, the epoch search must be performed This work was supported in part by the EC FP6-IST MAESTRO project, IST-507023. January 4, 2005 DRAFT