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Session F2: Advanced Software and Hardware Technologies for GNSS Receivers

Recent Developments and Proposed Revisions to Version 1.0 of the ION GNSS SDR Metadata Standard plus Implementation Status Report
Thomas Pany, Universität der Bundeswehr, München; Sanjeev Gunawardena, Air Force Institute of Technology
Date/Time: Wednesday, Sep. 21, 2:12 p.m.

The ION GNSS SDR Metadata Standard was developed to standardize the specification of sampled SDR data files in order to simplify the exchange of datasets and promote the interoperability of satnav SDR systems and spur further innovation [1]. Version 1.0 was formally accepted as an official Institute of Navigation Standard in January 2020.
GNSS sample data collection systems necessarily produce a wide array of file formats for various applications. These include multiple frequency bands, antenna elements, sampled data streams, precorrelation bandwidths, and bit depts. The files produced may embed multiple data streams – or multiple files containing a single data stream each. The SDR files themselves may be temporally split to ease the management of very large datasets (that can reach into multiple Terabytes for high-end systems). Some systems also embed other data such as from navigation sensors along with the sampled GNSS data. The ION metadata standard describes all of these possible data collection topologies using a hierarchical set of metadata classes. In Version 1.0, the metadata classes are described using eXtensible Markup Language (XML). The metadata specification is such that the methodology needed to unpack the samples in the correct format and present the samples into one or more streams for subsequent processing can be determined algorithmically. These capabilities are demonstrated in normative open source software that is included with the standard in a Git repository. To date, the standard has been adopted by commercial satnav SDR data collection systems [2-4] and processors [5-12]. All information pertaining to the standard can be accessed at sdr.ion.org.
This paper describes several advancements that have occurred since version 1.0 of the standard was released. This includes, 1) support for sample packing formats that are optimized for bitwise parallel processing [13], and 2) support for metadata specification using JavaScript Object Notation (JSON). Within the (former) GNSS SDR working group, a discussion will take place as to what extent these modifications shall be implemented. This paper will document the reasoning behind the decisions being made.
From the technical side, proposals made in [13] shall be analyzed: Shortcomings in describing periodic, synchronous timing relationships among heterogeneous streams, such as staggered sampling shall be improved by introducing a delay factor for sample streams. A means to override the default layout of stream sample bits within a lump by introducing a table-based layout scheme of a Lump shall allow more flexibility in describing the stored samples.
The paper shall be complemented by a concise overview of GNSS SDR projects currently employing or planning to employ the GNSS SDR standard.
REFERENCES
[1] Gunawardena, S, Pany, T, Curran, J. ION GNSS software-defined radio metadata standard. NAVIGATION. 2021; 68: 11– 20. https://doi.org/10.1002/navi.407
[2] TeleOrbit GmbH. (n.d.). GTEC©GNSS radio frequency front-end and MGSE record and replay device. https://teleorbit.eu/en/satnav/gtec/
[3] IFEN GmbH. (n.d.). SX3 GNSS software receiver. https://www.ifen.com/products/sx3-gnss-software-receiver/
[4] OHB Digital Solutions. (n.d.). GIPSIE: GNSS multisystem performance simulation environment. https://www.ohb-digital.at/bereiche/gnss-processing/gipsie
[5] Favenza, A., Linty, N., & Dovis, F. (2016, September). Exploiting standardized metadata for GNSS SDR remote processing: A case study. Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016), Portland, OR, 77–85. https://doi.org/10.33012/2016.14579

[6] Linty, N., Minetto, A., Dovis, F., Romano, V., & Hunstad, I. (2018, September). Investigation into the space weather event of September 2017 through GNSS raw samples processing. Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), Miami, FL, 4111–4124. https://doi.org/10.33012/2018.15921
[7] Lucas-Sabola, V., Seco-Granados, G., López-Salcedo, J. A., García-Molina, J. A., & Crisci, M. (2016, September). Demonstration of cloud GNSS signal processing. Proceedings of the 29th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2016), Portland, OR, 34–43. https://doi.org/10.33012/2016.14574
[8] Pany, T., Dötterböck, D., Gomez-Martinez, H., Hammed, M. S., Hörkner, F., Kraus, T., & Ebert, D. (2019, September). The multisensory navigation analysis tool (MuSNAT) – Architecture, LiDAR, GPU/CPU GNSS signal processing. Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute
of Navigation (ION GNSS+ 2019), Miami, FL, 4087–4115. https://doi.org/10.33012/2019.17128
[9] Rügamer, Alexander. (2018, September). Examples of usage of ION metadata standard. Presented at ION GNSS+ 2018, Miami, FL. https://s3.amazonaws.com/sdr.ion.org/Presentations_and_Publications/2018/Ruegamer__ION_Metadata_Examples_v03.pdf
[10] Rügamer, A., Meister, D., Van der Merwe, J. R., Otto, C., Stahl, M.,& Felber, W. (2017, May). Versatile and configurable GNSS interference detection and characterization station. Proceedings of the ION 2017 Pacific PNT Meeting, Honolulu, HI, 797–808. https://doi.org/10.33012/2017.15104
[11] Zhu, X., Chen, X., Ying, R., Zhan, S., Wang, Y., Fang, X., ... Yu, W. (2015, September). An innovative remote testing system for GNSS receiver based on IF sampled signal library of various scenarios. Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+
2015), Tampa, FL, 250–257.
[12] Gunawardena, S., "A High Performance Easily Configurable Satnav SDR for Advanced Algorithm Development and Rapid Capability Deployment," Proceedings of the 2021 International Technical Meeting of The Institute of Navigation, January 2021, pp. 539-554. https://doi.org/10.33012/2021.17808
[13] Clements, Zachary, Iannucci, Peter A., Humphreys, Todd E., Pany, Thomas, "Optimized Bit-Packing for Bit-Wise Software-Defined GNSS Radio," Proceedings of the 34th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2021), St. Louis, Missouri, September 2021, pp. 3749-3771.
https://doi.org/10.33012/2021.18015

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