Assessment of the Delay-Locked Loop Error due to Multipath Models Regarding a Deterministic-stochastic Channel and a GPS L1 Receiver Model for Kinematic Trajectories

Alexandra Avram, Noha El Gemayel, Volker Schwieger

Abstract:	The satellite receiver chain is analysed to perform an assessment of the Delay-Locked Loop (DLL) error in a multipath environment. For this purpose, a test bench is created and two multipath models are used. The first one is the fixed-offset model. It is a straight-forward implementation which allows to study the behaviour of the receiver regarding a constant error case. The second model is deterministic-stochastic and it is based on an existing one which is further developed. A deterministic model is appropriate when the system is well-known, whereas a stochastic one describes the uncertainties. Thus, for a multipath environment the mixture of these two leads to a result which is closer to reality. Within this paper, the deterministic part allows the environment modeling and the statistical one models the random scattering. The multipath channel impact on the signal is described on the three observables: signal strength, carrier shift and code phase shift. These quantitative changes which result from the multipath channel modeling are implemented to real hardware signals using the signal generator Spirent GSS7000. This signal generator allows the user to model the channel using input batch files describing signal attenuation as well as code and carrier shifts. The output signal is digitized by the 50 MHz RF front-end of a software receiver, IFEN SX3. Given its modular construction, the tracking engine of the receiver is further parametrized in order to evaluate the multipath error. With a code and carrier accuracy up to 20 cm, respectively one mm, the assessment results can be validated. Signal simulations with and without the implemented multipath models at different receiver velocities are performed. The multipath error is detected and quantified by means of multiple correlators. The behaviour of the Delay-Lock Loop in presence and absence of multipath is analysed.
Published in:	Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018) September 24 - 28, 2018 Hyatt Regency Miami Miami, Florida
Pages:	3552 - 3561
Cite this article:	Avram, Alexandra, Gemayel, Noha El, Schwieger, Volker, "Assessment of the Delay-Locked Loop Error due to Multipath Models Regarding a Deterministic-stochastic Channel and a GPS L1 Receiver Model for Kinematic Trajectories," Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), Miami, Florida, September 2018, pp. 3552-3561. https://doi.org/10.33012/2018.15871
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