Scintillation modeling for GPS-Wide Area Augmentation System receivers

A scintillation signal model and a Global Positioning System (GPS)-Wide Are a Augmentation System (WAAS) receiver model are developed. The scintillatio n signal model is based on a Nakagami-m distribution for intensity and a Ga ussian distribution with zero mean for phase. The GPS-WAAS receiver model i ncludes Link 1 (L1) GPS and WAAS carrier- and C/A-code-tracking loops, as w ell as semicodeless Link 2 (L2) carrier and Y-code tracking capabilities. T he results show that noncoherent delay locked loops (DLLs) typically used f or code tracking are very robust to both amplitude and phase scintillation. Carrier-phase-tracking loops are much more susceptible to scintillation, a nd the signal-to-noise threshold for reliable carrier tracking is very depe ndent on the scintillation strength. Fortunately, it appears that the worst case scintillation encountered at midlatitudes, including the United State s, does not significantly impact L1 carrier-tracking performance. Semicodel ess tracking of the L2 carrier is shown to be very fragile. Even weak scint illation can cause loss of L2 carrier lock for low-elevation satellites.