Combination of squared correlators for multipath mitigation in safety-of-life global navigation satellite systems receivers

This study presents a novel solution of DLL discrimination function for multiband global navigation satellite systems (GNSS) receivers, designed to cope with a multipath-prone environment in safety-of-life (SoL) applications. The solution is based on a combination of squared correlators (CSC) outputs, following an approach similar to that driving to the well-known, and patented, Strobe^TM discriminator. The proposed CSC discriminator features the novelty with respect to other `double-delta` architectures, usually covered by patents, still maintaining a light implementation (four correlators per channel, plus the prompt one); this comes at the cost of sub-optimal performance with respect to the classic Strobe^TM discriminator. The study presents the definition of the CSC solution in the context of a SoL receiver architecture, discusses the motivations for its design choices and shows an analysis of performance both in open-loop, basically employing the discriminator S-curve and the multipath error envelope, and in closed-loop, measuring the variance of estimated code phase and the statistics of the multipath-induced phase error. Performance of the proposed function are evaluated for the typical modulations of the GPS L1 and Galileo E1 systems, namely BPSK(1), BOC(1,1) and CBOC(6,1,1/11).