Unambiguous Synchronization Scheme for GNSS BOC(n, n) Signals

Galileo and Modernized GPS have included in their signal structures a new signal modulation: the Binary Offset Carrier (BOC), which multiplies a spreading code with a square wave sub-carrier. It creates a split spectrum with two main lobes shifted from the center frequency by sub-carrier. This modulated signal induces better tracking in white noise and better inherent multipath mitigation compared to the spreading code alone. However, it also makes acquisition more challenging and tracking potentially ambiguous due to its multiple peak autocorrelation function. This paper, instead of trying to find a generic solution, focuses on a specific BOC signal: the BOC(n,n). A novel tracking technique dedicated to BOC(n,n) signals has been developed by using a synthesized local cross correlation function between received BOC signal and local PRN. It completely removes the side-peak threating. Simulation results show that the combined tracking loops can eliminate false lock points. It also reduces the standard tracking deviation error and slightly degrade its probability of detection compared with the standard tracking algorithm.