Advancements in Multipath Mitigation for GNSS Receivers: Review of Channel Estimation Techniques

Multipath interference poses substantial challenges to global navigation satellite system (GNSS) receivers, leading to inaccuracies in the time of arrival (TOA) measurement of the line of sight (LOS) signal. Therefore, to mitigate the impact of multipath on receivers, the problem has been approached at several system development stages—signal design, reception, and processing. While efforts and advancements have been achieved over the years at each stage seeking navigation robustness, this article focuses on the signal processing stage by presenting a review of advanced multipath mitigation techniques using adaptive channel parameter estimation at the correlation level. The multipath mitigation literature often resorts to optimistic assumptions—high signal-to-noise ratio (SNR), static multipath channel, single fading channel distribution, and so on—while in real-world scenarios noise is prominent, the number of paths and their states vary at different rates, channels are nonstationary, along with other nonideal conditions. Moreover, it is important to directly compare different techniques to characterize their applicability and limitations. An analysis of adaptive algorithms is conducted for multipath mitigation applications.