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Communication Dans Un Congrès Année : 2009

Multipath effects on the GNSS repeater based approach : tracking loop discriminator impact on multipath mitigation

Résumé

This paper presents a study of the impact of different tracking loop discriminators on the precision of the indoor positioning carried out in order to evaluate multipath effects on the GNSS repeater based approach. In addition, antenna characteristics are considered. A previous work [1] evaluated the impact of multipath characteristics (power, delay and carrier phase) on the estimation of the distances in different indoor environments. Different antenna patterns were studied and significant differences were observed while changing characteristics like the pattern or the orientation of the repeater antennas. The goal of the present paper is to provide directions of optimisation of the multipath problem in indoor environments by combining the effects of the antenna characteristics, the multipath propagation mechanisms and the tracking code loop discriminator performances. The theory of the GNSS repeater approach, together with experimental results validating its principle was fully described in previous papers [2]. Briefly, it consists in using four GNSS repeaters in a sequential mode, with only one repeater transmitting at a given time. A transmission cycle is thus set up in order to carry out measurements of the pseudo-range jumps at the transition from one repeater to the next. After a complete cycle four such jumps are available and allow the indoor calculation, through a classical GNSS computation. However, as often indoors, the GNSS repeater based approach is strongly affected by multipath, the main problem being that their effects are difficult to evaluate and/or estimate [3]. Indeed, the multipath characteristics have fast variations in time and space, hence there is no exact model to eliminate it. In order to carry out multipath evaluation and optimisation we study the influence of multipath characteristics on the positioning precision. This study is performed in two steps: first, all the multipath components propagating between each repeater antenna and the indoor receiving antenna are determined using a propagation simulation software. Furthermore all the multipath rays are injected in a Matlab/Simulink GPS receiver simulator which evaluates the error on the pseudo-range caused by the multipath. The paper is organized as follows. Section 2 describes the simulations setup. The multipath propagation simulation software used in order to determine the multipath components characteristics is presented here, including the description of the propagation environment and of the considered antennas. The GPS receiver simulator, implemented using Matlab/Simulink is presented furthermore. Two different implementations of this receiver are described and compared. The first one is based on the usual Early-Late GPS tracking loop discriminator, while the second is based on an optimized discriminator [4] developed in order to mitigate the short multipath (with delays of less than 0.5 code chip), which are the ones occurring in typical indoor environments. Section 3 presents the simulation results of the predicted distance between each repeater and each receiving antenna position. A comparison of the impact of the two tracking loops is performed for two different types of repeater antennas, validating the theoretical performances of the optimized discriminator. Section 4 evaluates the precision of the positioning by estimating the impact of multipath components on the pseudo-range jumps at the transition from one repeater to the next. Finally, Section 5 summarizes the paper and concludes
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Dates et versions

hal-01314867 , version 1 (12-05-2016)

Identifiants

  • HAL Id : hal-01314867 , version 1

Citer

Anca Fluerasu, Nabil Jardak, Alexandre Vervisch-Picois, Marco Boschetti, Nel Samama. Multipath effects on the GNSS repeater based approach : tracking loop discriminator impact on multipath mitigation. ENC-GNSS 2009 : European Navigation Conference - Global Navigation Satellite Systems, May 2009, Naples, Italy. pp.1 - 8. ⟨hal-01314867⟩
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