Performance Analysis of Different Noncoherent Integration Alternatives for Weak GPS Signal Acquisition

Unaided weak Global Positioning System (GPS) signals acquisition requires both long coherent integration time and a great amount of noncoherent integration operations. The acquisition is declared if the integration result crosses a predetermined threshold. In this paper, four different noncoherent integration alternatives using different approaches to compute the noncoherent integration at each noncoherent integration step are introduced. The performance in terms of detection and false alarm probabilities is investigated. For weak signal acquisition, it is shown that Alternative 2 is nearly 3dB more sensitive than Alternative 1, and Alternatives 3 and 4 are better than Alternative 1 but worse than Alternative 2. Examples are given using Alternatives 1 and 2. They illustrate how to decide the thresholds to achieve a probability of detection for a given probability of false alarm, and serve as a guide to determine the combination of the coherent integration time and the number of noncoherent integrations. The comparison between Alternatives 1 and 2 is also processed, and the statistics of simulations have verified the conclusion that Alternative 2 is nearly 3dB more sensitive than Alternative 1.