Multipath mitigation in SoL environments using a combination of squared correlators

The disruptive effects of multipath around the receiver antenna are well known and proved by a very wide GNSS literature. In addition, multipath robustness is one of the first signal characteristics taken into account in the process of signals definition. The rejection of the multipath effects becomes an even more sensitive issue in Safety-of-Life (SoL) environments, when the signal reliability is a crucial requirement. Multipath mitigation has been faced with a great number of approaches, from antenna-based techniques to different families of signal processing techniques. For example, the global multipath cancellers are simple signal processing methods that adopt specific DLL discrimination functions robust with respect to the signal distortions. However, their principal architectures are covered by patents, so that sometimes the need arises to identify non-patented architectures, still maintaining performance and implementation simplicity comparable to their patented counterpart. This paper presents a novel DLL discriminator belonging to the set of global multipath cancellers; it is referred to as Combination of Squared Correlators (CSC). The CSC discriminator does not fall into the wide family of patented architectures, while combining at the same time novelty and implementation simplicity, employing four correlators per channel (i.e., early, late, very-early, and very-late), as in the case of the patented Strobeâ„¢ architecture. In this paper the performance of the CSC architecture are investigated, both theoretically and via simulation test. Open loop performance have been tested by the analysis of the multipath error envelope, while the variance of estimated code phase jitter and the multipath-induced average code phase error are the parameters chosen to test the solution in closed loop conditions. The estimated C/N0 ratio produced by the receiver on the basis of the post-correlation samples has also been observed as a comparison of different discriminators. Moreover, the discriminator has been tested in realistic simulation models of the multipath environment, namely the ITU-standardized Satellite Navigation Multipath Channel Model, developed to simulate Earth-space land mobile telecommunication systems in the L band. All the results demonstrate that the CSC discriminator obtains performance just slightly worse than those given by the Strobeâ„¢ one, maintaining a similar degree of complexity.