Post-correlation semi-coherent integration for high-dynamic and weak GPS signal acquisition

Abstract

Acquisition and ultimate tracking of a weak GPS signal faces several technical challenges, notably, possible data bit sign reversal every 20 ms and tolerable frequency error inversely proportional to the integration interval. Brute force search over all possible combinations of the unknown values is computationally prohibitive. Assisted GPS relying on external infrastructure for timing, data bit, and frequency error information is costly. Coherent techniques such as the block accumulating coherent integration over extended interval (BACIX) have recently been proposed to increase coherent integration. Although efficient, such coherent methods may still be too expensive except for high-end receivers and may not maintain the SNR performance when there are large frequency changes over the extended integration interval.