Analysis and simulation of vector tracking algorithms for weak GPS signals

In this paper, the vector delay lock loop/frequency lock loop (VDLL and VFLL) tracking algorithm for tracking the L1 civilian GPS signal is analyzed and simulated. In vector mode, the navigation processor controls the code and carrier numerically controls oscillators (NCOs) replacing the tracking loops. A major advantage of this method is that after once a good position, velocity and time (PVT) solution is available, all GPS signals are continuously tracked even under weak (or no) signal conditions. The advantages of the vector DLL/FLL based architecture over traditional methods are explained. The ability of the vector tracking algorithms to rapidly reacquire blocked signals is analyzed using the real GPS data added the simulated noises.The vector tracking algorithms performance is also compared to traditional methods using tracking loops. The VDFLL is shown to outperform the traditional methods.