Multilag Frequency Estimation for High-Order BOC Signals in the Acquisition Stage

Abstract

In the context of global navigation satellite systems, this paper addresses the problem of refining the Doppler frequency estimation provided in the acquisition stage for highorder binary offset carrier (BOC) signals in post-correlation. The refinement of Doppler frequency must be done because the estimation obtained from the acquisition stage is not usually accurate enough to track the signal in the tracking stage. In this work, we only use the cross-ambiguity function (CAF) created in the acquisition stage to perform the refinement. A least squares estimator has been already applied to mitigate this problem. We propose a new technique, referred to as multilag least squares estimator, which improves the performance of the least squares estimator by exploiting the autocorrelation shape of high-order BOC signals. Moreover, the Cramer-Rao bound and the expected Cramer-Rao bound are derived as benchmark to compare the performance of the least squares and multilag least squares estimators.