A GNSS meta-signal SAGE-based multipath-mitigating loop design

Abstract

A major challenge suffered by Global Navigation Satellite System (GNSS) receivers is the multipath interference, which results in serious tracking performance degradation and increased positioning errors. Growing evidence suggests that wide-bandwidth signals and multi-antenna technology are set to become two vital factors to improve the GNSS multipath mitigation, leading to the concept of meta-GNSS signal and multi-dimensional processing. To estimate the time delay of line-of-sight (LOS) ray in a multipath environment, we propose a meta-signal Space Alternating Generalized Expectation (SAGE) based locked loop (SAGELL) design, which exploits the high-resolution of the meta-signal together with the characteristics from spatial and temporal domains. The SAGELL design comprises two main setups: the SAGE-based discriminator and combinational loops. Benefiting from the multi-dimensional processing and meta-signal bandwidth, the SAGE-based discriminator first estimates the LOS ray and the multipath rays in single side-band components and achieves the global estimates of the dual side-band components coherently. Aiming to accurately track each ray of the meta-signal, we further close the SAGELL via angle, code phase, and carrier phase locked loops to filter and predict the estimates. The proposed GNSS meta-signal multipath-mitigating loop design allows for GNSS high-precision discrimination and tracking in multipath scenarios, even in the presence of highly correlated rays, as confirmed by the numerical results.