Simulation Study of GPS Phase Scintillation

Signal phase measured by GPS signal processors is crucial for high-resolution range measurement. However, the measured signal phase must be corrected for the the dispersive phase advance imposed by the earth’s ionosphere. Dual-frequency measurements exploit frequency dependence to isolate and correct the ionosphere-induced phase change. The correction is proportional to total electron content (TEC), which can be used as an ionospheric diagnostic in its own right. New theoretical results have provided a means of e¢ ciently generating multi-frequency scintillation realizations over the complete range of observed GPS disturbance levels. A compact parameterization allows space-to-time translation consistent with observed temporal variations. Moreover, the stochastic TEC variation that initiates the phase-screen realization is e¤ectively TEC truth, whereby scintillation-induced TEC errors can be evaluated. TEC truth also provides a means of assessing the relation between deep fades and associated rapid phase changes that are often identi…ed as cycle slips. We assess the conditions under which scintillation imposes irrecoverable TEC errors. Because the simulations are free of scintillation-induced processor distortions, the errors are e¤ectively lower bounds.