The growing demand of location, navigation and positioning services is boosting the development of new signals and modulations that will be adopted by new Global Navigation Satellite Systems (GNSS), such as the European Galileo, the Chinese Compass and the modernized GPS. A common feature of these new modulations is the presence of two channels, the data and pilot components, that separately carry the navigation message and the ranging information. Three different techniques, noncoherent combining, coherent combining with sign recovery and differentially coherent combining, are analyzed for the joint acquisition of data and pilot signals. For each acquisition strategy the probabilities of detection and false alarm are provided. In particular closed-form expressions for the probabilities of coherent channel combining and of the differentially coherent integration strategy are derived. To the best of our knowledge these expressions are new. Monte Carlo simulations are used to support theoretical analysis demonstrating the accuracy of the proposed models.
Carrier phase-based positioning using Global Navigation Satellite System (GNSS) signals can provide centimeter-level accuracy; however, to do so requires robust, continuous tracking of the phase of the received signal. The phase-locked loop is typically the weakest link in GNSS signal processing, with frequent cycle slips and loss of lock occurring at lower signal-to-noise ratios. One way to improve the signal-to-noise ratio is to increase the coherent integration time; however doing so reduces the loop update rate, thereby degrading performance. This paper investigates this trade-off between sensitivity and loop update rate by investigation of the Kalman filter-based tracking loop. It is shown that it is possible to choose an optimal integration time for a given application. A relatively straightforward procedure is given to determine this optimal value. The results are confirmed through real-time kinematic processing of live satellite signals.
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