An analytical model of code-tracking performance for next-generation GNSS modulations

Abstract

Precorrelation bandlimiting, sampling, and quantization (BSQ) are three fundamental functions of receivers for global navigation satellite system (GNSS) signal processing. Analytical models have been developed to evaluate the implementation losses due to different combinations of these parameters for legacy modulations such as BPSK. However, the performance metric was losses of effective carrier-to-noise ratio in dB, instead of performance degradation of a delay-locked loop (DLL) used for code-tracking. This paper proposes an analytical model to predict the DLL performance with the loss of RMS tracking error in meters as the performance metrics. The signal model & assumptions and canonical form of DLL are first introduced. Then, analytical model is derived for DLL tracking accuracy and the performance metrics, tracking loss is defined. Finally, simulation results of two next-generation modulations for GPS and Galileo, namely CBOC and TMBOC, are presented.