Exclusion of Multipath-Affected Satellites Using Early Late Phase

This paper presents experimental results of detecting multipath using a recently proposed parameter, early late phase (ELP). The paper shows that positioning error caused by multipath can be reduced by excluding the satellites detected as experiencing multipath from the navigation solution, except where the exclusion causes a significant increase in dilution of precision. Performance of this ELP-based satellite exclusion was compared with standard wide correlators, along with narrow and double delta correlators. It was found that narrow and double delta correlators may in fact increase error when a reflected signal is stronger than the LOS (a scenario possible where the LOS is attenuated) or when multiple reflections are received from the same satellite. In these cases, ELP can still detect multipath and satellite exclusion can mitigate multipath-induced error. Even in more usual cases, satellite exclusion was shown to outperform narrow correlators and performed as well as double delta correlators. However, the exception to this is when there is another satellite affected by multipath not detected using ELP and hence not removed from the solution. In this case, the error may in fact increase by removing one multipath-affected satellite because the multipath biases may be partially cancelling each other.