Performance evaluation of multipath mitigation techniques for critical urban applications based on a land mobile satellite channel model

The use of GNSS for critical terrestrial applications requires adapted integrity monitoring algorithms for either safety or liability issues. Prior to the design of integrity monitoring algorithms, it is necessary to characterize the nominal error model of every error source affecting the pseudorange measurements. This paper focuses on describing a way to calculate the contribution of the multipath to the nominal error model by a set of simulations based on an urban channel model and a realistic GNSS tracking loop simulator. To improve the accuracy of the positioning, multipath mitigation techniques are usually implemented in the receivers. This paper assesses the performances of the Narrow Correlator, the Double-Delta and the A Posteriori Multipath Estimation techniques in an urban environment and provides their multipath residual nominal error model as a function of the satellite elevation angle. A relationship between quality monitoring indicators and the multipath estimation technique (APME) is also discussed. The results of this paper are obtained by simulating an actual urban railway environment and therefore can be taken as inputs for the design of GNSS integrity monitoring algorithms for rail users. The same approach can be used for the determination of the nominal error model for other terrestrial application subject to simulating an adapted channel.