Multi-band Multi-site GNSS RFI Monitoring Results after a Year of Operation

An international network of Radio Frequency Interference (RFI) monitoring stations covering all L-band Global Navigation Satellite System (GNSS) signals has provided large amounts of data on the occurrence rates and characteristics of the detected sources. As the stations are primarily deployed by roadways the measurements include a large number of Personal Privacy Device (PPD) style jammers as well as an unexpectedly large contingent of spurious emissions and co-authorized users. Important results include the high levels of variability in month-to-month activity levels of sites indicating that site survey activities must be conducted over longer periods to obtain accurate occurrence rate information.acceptedVersio

Automatic GNSS RFI Classification Challenges

This article describes the real-world challenges that are encountered when trying to automatically categorize and classify the radio frequency interference (RFI) events captured in the GNSS signal bands by an international network of monitoring stations covering all L-band navigation signals. While signals frequently fall into the often-discussed categories such as 'chirp', 'continuous wave', or 'wideband noise', there is a large and growing number of modulations encountered in reality, both intentional and unintentional. These bear varying degrees of resemblance to the aforementioned traditional categories. Work presented herein focuses on some of the main complications encountered when categorizing multiple years of GNSS RFI event data, and the algorithmic approaches used to proceed with classification in these conditions.publishedVersio

Characterization of the GNSS RFI Threat to DFMC GBAS Signal Bands

This article presents analysis results from a long-term multi-site Global Navigation Satellite System (GNSS) Radio Frequency Interference (RFI) monitoring campaign in the context of Ground Based Augmentation System (GBAS) Dual Frequency Multi Constellation (DFMC) concept operation. GBAS resilience against unintentional RFI is an important area for investigation as the ground station receivers often must operate adjacent to high-traffic roads where chances of being affected by RFI are high. To be able to develop algorithms and reaction strategies necessary to ensure continuity and availability of service, knowledge of interference signal characteristics and frequency band/bands affected, as well as relative occurrence rates between the considered frequencies and frequency combinations, is necessary. The analysis presented in the article covers the prevalence and properties of the RFI events observed on the GPS L1 and L5 and the Galileo E1 and E5a frequency bands that are considered by the on-going DFMC GBAS concept development initiatives. Due to being spectrally adjacent, the observed event analysis is also carried out for the Galileo E5b and GLONASS G1 frequency bands. The article also addresses the issue of spectral occupancy distribution of the observed events and presents new interesting RFI event types captured during the considered monitoring period.publishedVersio

Differential ZTD estimation based on high spatial resolution NWP data for the Nordic countries

This paper contains results from a study where Numerical Weather Product (NWP) data provided by MET Norway are used to estimate the differential zenith tropospheric delay (dZTD) for an area covering Scandinavia, Finland and the Baltic countries. The NWP data have a high spatial resolution of 2.5 × 2.5 km, and the estimated dZTD for the grid positions allow for calculation of the tropospheric gradient on short baselines. The results give an indication of how large dZTD values that can be observed for baselines up to 20 km, and where the largest events are located within the coverage area. The motivation for this investigation is to better understand the characteristics of this phenomena and how it might impact high precision and/or high integrity GNSS-based navigation systems in these regions.acceptedVersio

Combining visual, pedestrian, and collaborative navigation techniques for team based infrastructure free indoor navigation

Peer reviewe

GNSS-Denied Navigation using Direction of Arrival from Low-Cost Software Defined Radios and Signals of Opportunity

This paper describes a novel navigation system for outdoor navigation in conditions where reliable satellite navigation cannot be assumed. It is build around inexpensive of-the-shelf hardware and could be used with several different signal types, allowing flexibility in usage. The system is currently in a proof-of-concept stage, and this paper shows that there are promising preliminary results.acceptedVersio

A multi-site quad-band radio frequency interference monitoring alerting and reporting system

This paper reviews the motivation behind and development of a deployable Radio Frequency Interference (RFI) detection, alerting and reporting system which simultaneously monitors all Global Navigation Satellite System (GNSS) L-band signal transmission for disruption, captures interference events, characterizes them, notifies stakeholders of event occurrence and lastly marshals the captured data to cloud storage. Results of a multi-site international deployment program are presented and discussed. © 2020 German Institute of Navigation - DGON.Peer reviewe

Getting better all the time - The Continued Evolution of the GNSS Software-Defined Radio

Software Defined Radio (SDR) has an infinite number of interpretations depending on the context in which it is designed and used. By way of a starting definition the authors choose to use that of ‘a reconfigurable radio system whose characteristics are partially or fully defined via software or firmware’. In various forms, SDR has permeated a wide range of user groups, from military, business, academia and to the amateur radio enthusiast

RFI Considerations for Utility of the Galileo E6 Signal

Peer reviewe

Radio-Frequency Interference Considerations for Utility of the Galileo E6 Signal Based on Long-Term Monitoring by ARFIDAAS

The extent to which navigation signals in the E6 band may be impacted by shared spectrum allocations might be underappreciated. This paper presents top-level observations from a multi-year international radio frequency interference (RFI) monitoring project covering all L-band global navigation satellite system (GNSS) signals with specific focus on the challenges facing the E6 band. The context of this paper is the assumption that most users will be non-authorized and have access to only the open data-bearing signal component and not the encrypted pilot of the E6 Galileo signal. In virtually all locations where the Advanced RFI Detection, Analysis, and Alerting System (ARFIDAAS) monitoring stations were deployed, frequent disruption of the E6 band from systems such as radar installations or other authorized users of the spectrum was observed. In the presented paper, an effort is made to put the observations in the context of the expected use cases of the E6 signal.publishedVersio