The IEC 61108-7 standard focuses on the minimum performance of shipborne receivers using Satellites Based Augmentation System (SBAS) L1 signals to be compliant to the performances within IMO Resolution A.1046(27). Apart from the minimum performance requirements, the standard specifies testing methods and a full set of scenarios with their pass/fail criteria. To verify the feasibility of the tests defined in the standard, a comprehensive test campaign has been carried out in a joint effort by European Satellite Services Provider (ESSP) and the European Commission Joint Research Centre (JRC), under the coordination of the European Union Agency for the Space Programme (EUSPA). This paper presents an assessment of the validity and appropriateness of the test scenarios and minimum performance requirements specified in the future IEC-61108-7 standard. To perform the campaign, dedicated setups have been designed and implemented at the JRC and at ESSP laboratories, where live and simulated GPS+SBAS signals have been used. For the analysis, all the Test Cases (TCs) described in the standard were implemented and two commercial devices were tested. From the results, it emerged that all the TCs were properly designed and implemented, therefore confirming the feasibility of the tests defined in IEC 61108-7.

Spoofing attacks pose a threat to drones that can lead to their crash or takeover. As a countermeasure, the European Space Agency has implemented the Timed Efficient Loss-tolerant Authentication (TESLA) broadcast protocol in the Galileo Open Service Navigation Message Authentication (OSNMA) to detect such events. This study explores the application of TESLA in detecting spoofing attacks targeted at drone swarms that rely on positioning systems utilizing ultra-wideband (UWB) technology. The results of our experiments reaffirm that UWB-based positioning systems are not automatically invulnerable from spoofing attacks and that cryptographic methods such as TESLA are required to provide a layer of protection against spoofing attacks to detect them effectively.

Galileo Open Service Navigation Message Authentication (OSNMA) has been transmitted stably over the last years and is expected to be declared operationally in the next months. While the protocol is very flexible, most of the parameters, such as key and tag sizes and cryptographic functions, have been already fixed in view of the operational declaration. However, some degree of flexibility remains in the tag and cross-authentication sequence. The cross-authentication sequence defines the satellites “cross-authenticated” by an authenticating Galileo satellite and is one of the main properties of the OSNMA protocol. It allows authenticating nearby Galileo satellites for higher redundancy against losses, authenticating data from satellites not connected to ground and therefore not transmitting OSNMA, and authenticating GPS or other data in the future. It has a significant impact on OSNMA performance: if the sequence is too long, many cross-authenticated satellites will not be seen by the users, limiting the optimal use of the OSNMA bandwidth, and with major impact in TBA (Time Between Authentications) and Time To First Authenticated Fix (TTFAF). If the sequence is too short, several non-connected but visible satellites may remain unauthenticated, also degrading performance. This paper presents an analysis with real SIS data from different cross-authentication sequences transmitted by Galileo over the last months, involving different tag distribution and number of cross-authenticated satellites including open-sky static, dynamic and urban environments. The work will show the degradation with suboptimal cross-authentication sequences and identifies current bottlenecks, proposing some recommendations for future sequences.

One year after Galileo High Accuracy Service (HAS) Initial Service declaration by the European Commission, this article present Galileo HAS accuracy and convergence comparative performance assessment between two different user algorithm configurations: static and dynamic. The assessment was conducted with two Galileo HAS User Terminal in parallel fed by the same antenna installation to obtain accuracy and convergence for the same period of time. The Galileo HAS User Terminal is a portable and autonomous device powered by a triple-frequency Galileo and GPS receiver and calculates a single (Galileo) or multi-constellation (Galileo + GPS) Galileo HAS using the Performance Characterization User Algorithm developed for the European Union Agency for the Space Programme (EUSPA). The performance assessment is completed with additional analysis in post-processing using a Precise Point Positioning (PPP) engine implementing the same algorithm than the User Terminal fed with International GNSS Service (IGS) stations observables and HAS Internet Data Distribution (IDD) corrections. The analysis is enhanced with an additional postprocessing analysis using the same IGS stations and CNES corrections.

Results for static conditions, assuming zero velocity in the Kalman filter, deliver accuracy performance at decimeter level 68% both horizontal and vertical. Results with the dynamic configuration, with a Kalman filter adaptable to changes in user velocity and fit for dynamic applications, indicate slightly over one decimeter 68% both horizontal and vertical. This article also compares both static and dynamic results vs. the Galileo HAS Service Definition Document (SDD) Appendix E typical positioning accuracy performance and presents the convergence time, or time to first precise fix, against positioning horizontal and vertical thresholds.

The purpose of this paper is to analyze the reaction of a real-time hardware multicorrelator GNSS receiver in realistic environments. In particular, we investigate how the GNSS signal correlations are distorted in two vehicular scenarios. The scenarios were recorded with a multi-frequency bit grabber and playback in the laboratory. The test campaigns were performed driving in two contrasting propagation environments. Rotterdam downtown was chosen to assess the multipath in challenging urban conditions while Nieuw-Vennep was selected as an open-sky/rural environment. The objective is to characterize the multipath of the received signal using a high-end GNSS receiver able to store 41 correlator outputs. The multipath error is estimated by comparing a local reference of the correlation function, which is estimated by using a GNSS simulator in the absence of GNSS disturbances, to the correlations estimated by the GNSS receiver in the vehicular scenarios. Two methods are considered. The first one consists in computing the error between the reference correlation function and the estimated ones. We evaluate the impact of the multipath on the temporal domain. The second one is based on estimating the multipath by implementing a Non-linear Least Squares estimator. The estimator provides reliable information about the power of the direct and reflected signals. We analyze the differences and similarities between both scenarios for several satellites having different elevations.