Long GNSS Secondary Codes Acquisition by Characteristic Length Method

Global Navigation Satellite System (GNSS) receiver evolution moves through the paths of interoperability among different satellite systems and the support of modern composite signals. To improve the receiver accuracy, the tracking sensitivity, and the resilience versus jamming, modern signals have introduced dual (pilot plus data) components. Pilot signals design on L1 carrier for GPS, BeiDou (phase 3), and Quasi-Zenith Satellite System (QZSS) are implemented by tiered codes, with a very long Secondary Code (SC), which can be difficult to acquire. This article will analyze and validate an efficient algorithm for secondary code phase estimation, with the objectives to minimize the total dwell time and to limit the processing complexity. Details will be provided about the performance tradeoff versus other classic algorithms, based on the exhaustive construction of power histograms, for all the SC phases. A method for fast reacquisition of the SC phase, based on time propagation, will be also illustrated to extend the practical usability of the estimator under difficult conditions, characterized by obscurations and signal impairments, typical of automotive scenarios.