Feasibility Analysis of Different Airborne Architectures for DFMC GNSS: How to Consolidate the Different Architecture Options?

Andreas Lipp

Abstract:	With exception of very few cases, GNSS-based positioning and navigation systems in aviation currently exclusively use the GPS C/A code on the L1 frequency for positioning and integrity determination. With the advent of other core satellite constellations, such as GLONASS, GALILEO and Beidou, more possibilities exist and have been proposed in various combinations. A number of papers have been proposed on the topic, each optimising for an individual augmentation, scenario, flight phase or system component. The airborne subsystems on the other hand become more and more integrated and will have to flexibly shift between the different modes of operations or even provide several solutions in parallel. They are also less- and less providing a stand-alone navigation solution and will be more integrated with other aircraft sensors. Optimising on receiver basis only is thus difficult. The current development of dual-frequency, multi-constellation ABAS, SBAS and GBAS standards has been performed mostly independently and led to differing solutions between the three augmentations. Duplicate processing with increased processing power and storage requirements and a high number of required processing modes are the consequences for future airborne applications. This paper therefore proposes another approach. It addresses the airborne functionality from an operational need in the different flight phases, considers the possible regulatory constraints and tries to find the least complex and most scalable solution across the entire spectrum of needs. It is likely that this approach will not lead to optimal performance for each individual phase or navigation mode, but the goal is to provide sufficient performance at the lowest required complexity. It also considers that solutions need to be robust, extensible and interoperable concerning support of different augmentations (ABAS, SBAS and GBAS) and the present and future navigation signal availability. Key considerations are based on: • TSE performance as opposed to current focus on NSE performance. This approach is already being used in the GBAS GAST-D standards; • A potential separation of positioning architecture from integrity determination architecture. In this way noise on the position solution can be controlled independently from the monitoring process at the cost of adapting the integrity process to always relate to the signals actually used for positioning; • The need to limit the number of possible mode changes, as they increase complexity and certification effort and hamper scalability of solutions; • Considerations of extensibility to future signals of opportunity; • Operational requirements to maintain the backwards compatibility with legacy systems and provide outputs suitable for the PBN and PBAOM concepts; • Maintaining a clear separation of positioning and navigation tasks in both systems and standards; The paper provides a first set of considerations for wider discussion and further work, notably in the frame of future SESAR development activity. It takes into account the GNSS-related resolutions of the 13Th ICAO Air Navigation Conference and the existing state of development of dual-frequency, multi-constellation aviation augmentations. The current development of dual-frequency, multi-constellation ABAS, SBAS and GBAS standards has been performed mostly independently and led to differing solutions between the three augmentations. Duplicate processing with increased processing power and storage requirements are the consequences for future airborne applications.
Published in:	Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019) September 16 - 20, 2019 Hyatt Regency Miami Miami, Florida
Pages:	1106 - 1123
Cite this article:	Lipp, Andreas, "Feasibility Analysis of Different Airborne Architectures for DFMC GNSS: How to Consolidate the Different Architecture Options?," Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019), Miami, Florida, September 2019, pp. 1106-1123. https://doi.org/10.33012/2019.17045
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