SBAS L5 Enhanced ICD for Aviation: Definition and Preliminary Experimentation Results

J. Fidalgo, M. Odriozola, M. Cueto, A. Cezón, J. Caro, C. Rodriguez, D. Brocard, J.C. Denis, E. Chatre

Abstract: The SBAS Interoperability Working Group (IWG) was formed by the different SBAS service providers to ensure that SBAS systems are compatible and to plan future enhancements. Nowadays its main goal is to contribute to the elaboration of a new standard able to augment up to 4 GNSS constellations simultaneously, and to offer new services for dual frequency (L1/L5) users. For that purpose, an Enhanced SBAS L5 ICD is currently under consolidation in the frame of the IWG. Two ICD families were firstly under consideration by IWG: • UDRE (User Differential Range Error) ICD family, aimed at defining a SBAS L5 ICD model as similar to the current SBAS L1 ICD as feasible. • DFRE (Dual Frequency Range Error) ICD family, proposed in Walter et al. (2012), whose main objective was to simplify the number of messages and their structures as much as possible, eliminating the fast corrections and sending a single correction message per satellite and a MT6-equivalent message with DFRECI and updates of DFREIs every 6 seconds. After a period of analysis and trade-off, see Cueto et al. (2013), an agreement has been reached at IWG mid-2013 in order to work on a unified SBAS L5 ICD, called from herein SBAS L5 Enhanced ICD, providing the combined advantages of both candidates ICD’s: • The advantages of UDRE ICD regarding dynamic capability (i.e. multiple DFREI’s update) upon system events, allowing mitigating the risk of continuity events at user level. • The advantages of DFRE ICD regarding simplicity and nearly deterministic scheduling state conditions. This paper provides a summary of the definition and preliminary experimentation results on the robustness and expected performances of the SBAS L5 Enhanced ICD achieved in the frame of PROSBAS (Prototyping and Support to Standardization of SBAS L5 Multi-Constellation Receiver) project’s related activities. This project, funded by the European Commission, is technically managed by ESA (EGNOS Project Office), and the PROSBAS Industry Consortium is led by GMV. Despite the fact that PROSBAS project covers aviation and maritime domains, this paper is focused on the aviation activities developed in the project. The aforementioned results have already been presented to IWG, and feedback from IWG has been taken into account in the developed analysis. The strategy followed to properly define and validate the SBAS L5 Enhanced ICD, as well as to develop a proper experimentation to study the behaviour of this ICD, has been based on the following main steps: • Definition of the Enhanced ICD. • Development of PROSBAS service provider and receiver prototypes including the implementation of the SBAS L5 Enhanced ICD. • Definition of the test plan, including Key Performance Indicators (KPIs), in order to analyse the robustness and expected performances of SBAS L5 Enhanced ICD. • Analysis of the results of the different tests. • Provision of recommendations for the SBAS L5 ICD following the results´ analysis. The following aspects of the SBAS L5 Enhanced ICD will be analysed and presented in this paper: • Message sequencing & bandwidth: The objective of this aspect is to analyse the message sequence and bandwidth use of the SBAS L5 Enhanced ICD, including the analysis of update intervals and time-outs fulfilment for the different messages. • Robustness at service provider and receiver levels: the robustness of the Enhanced ICD will be analysed upon different aspects, such as alerts, message loss, increase of integrity parameters, constellation degradation, transition modes. • Time-to-alert analysis: The objective of this experimentation is to analyse the fulfilment of Time To Alert (TTA) requirement of the SBAS L5 Enhanced ICD. • Constellation expandability to up to four constellations, by analysing the performances achieved vs. the number of constellations considered. • Nominal conditions performance analysis, by analysing the performances (integrity, availability, continuity and TTA) achieved with the Enhanced ICD model for nominal conditions. The main objective of the experimentation presented in this paper is to assess that the following preliminary conclusions (based on preliminary analyses) are still applicable: • SBAS L5 Enhanced ICD has been demonstrated to be robust upon all the criteria analysed. • SBAS L5 Enhanced ICD has at least, similar performances to DFRE ICD, giving rise to the following preliminary conclusions on expected performances: - LPV-200 VAL = 35 m. limit is feasible even for one constellation. - Cat I = 10 m. The feasibility of this service will be analysed. - SBAS L5 Enhanced ICD could fulfil SBAS L5 mission availability /continuity /TTA /accuracy for EGNOS V3 reference conditions. Further analyses are planned to consolidate and extend the preliminary conclusions presented in this paper. These activities will be developed as part of PROSBAS.
Published in: Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014)
September 8 - 12, 2014
Tampa Convention Center
Tampa, Florida
Pages: 3289 - 3298
Cite this article: Fidalgo, J., Odriozola, M., Cueto, M., Cezón, A., Caro, J., Rodriguez, C., Brocard, D., Denis, J.C., Chatre, E., "SBAS L5 Enhanced ICD for Aviation: Definition and Preliminary Experimentation Results," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 3289-3298.
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