WAAS Receiver Carrier Tracking Loop and Data Demodulation Performance in the Presence of Wideband Interference

Abstract

The Minimum Operational Performance Standards (MOPS) for GPS I Wide-Area Augmentation System (WAAS) airborne equipment [l] specifies an interference mask and minimum signal conditions that will be valid for all phases of flight. In addition, demodulated WAAS word error requirements are specified. In support of the RTCA Special Committee (SC)-159 WAAS MOPS activities, a detailed phase-locked loop carrier tracking simulation and analysis for the WAAS satellite signals was performed using the current link budget assumptions. The high-fidelity, nonlinear carrier tracking loop simulations include the Viterbi decoder, and provide word error, bit error, and cycle slip rates as a function of the carrier to noise-plus-interference ratio. Based on the simulation data, it appears that there is approximately a 1 dB link budget gap, which must be addressed by the appropriate industry/government committees.