Receiver-Level Robustness Concepts for EGNSS Timing Services

Martti Kirkko-Jaakkola, Sarang Thombre, Salomon Honkala, Stefan Söderholm, Sanna Kaasalainen, and Heidi Kuusniemi, Hein Zelle and Henk Veerman, Anders Wallin, Kjell Arne Aarmo and Juan Pablo Boyero

Peer Reviewed

Abstract:	GNSS-based time transfer is utilized in various critical infrastructures as it provides important advantages which are being increasingly exploited. In this paper, we present the various implementation options for robust timing service concepts based on European GNSS (EGNSS), i.e., Galileo and EGNOS, that are expected to further foster the use of EGNSS timing; this concept can make use of the redundancy of measurements and of available GNSS constellations. The stability properties of the local oscillator, which are known to the designer, are also exploited. The algorithms are developed to account for cases where several measurement faults occur simultaneously, which is a possible scenario in land-based reception conditions. Furthermore, we derive time protection level equations to quantify the integrity of the GNSS time solution as a function of the false alarm and missed detection probabilities as well as the maximum number of simultaneous outliers to be accounted for. Some of the considered fault scenarios can only be detected but not rectified by the algorithms: in such case, holdover, i.e. processing based on the local oscillator alone, is triggered. Thus, the performance in these scenarios is dependent on the stability of the local oscillator; in this paper, the analysis is based on a low-cost temperature-compensated crystal oscillator. The effect of the robustness concepts is illustrated with a set of experiments which show that when implemented in a timing GNSS receiver, the algorithms presented can deal with failures that affect individual satellites or even an entire constellation. Local disturbances affecting the receiver can also be effectively detected. Specifying EGNSS timing as proper services along with well-defined procedures for testing receiver compliance paves the road for standardizing and certifying robust EGNSS timing receivers, which would be beneficial for many applications and in particular in safety or liability critical use cases.
Published in:	Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) September 25 - 29, 2017 Oregon Convention Center Portland, Oregon
Pages:	3353 - 3367
Cite this article:	Kirkko-Jaakkola, Martti, Thombre, Sarang, Honkala, Salomon, Söderholm, Stefan, Kaasalainen, Sanna, Kuusniemi, Heidi, Zelle, Hein, Veerman, Henk, Wallin, Anders, Aarmo, Kjell Arne, Boyero, Juan Pablo, "Receiver-Level Robustness Concepts for EGNSS Timing Services," Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 3353-3367. https://doi.org/10.33012/2017.15137
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