## 3 Results and Discussion  
In the analysis, the performance of the three solutions in terms of the 2D position error and fix type was compared, also in relation to the number of satellites. The current limitations of receivers using signals from only OSNMA-authenticated satellites in terms of availability and accuracy are discussed in relation to potential use cases involving highly automated driving. Figure 3 shows the proportion of position types encompassing all driving conditions, ranging from open sky in motorways and rural roads, through hilly and forested environments, to suburban and urban areas. It can be seen that the percentage of fixed solutions (RTK fix) was 89.92% when all GPS L1/L2 and Galileo E1/E5a satellite signals were used (OSNMA off). The percentage was slightly lower in the OSNMA loose configuration (89.59%). Regarding the receiver with OSNMA strict settings (use of authenticated Galileo signals only, no GPS signals), the percentage of (now authenticated) RTK-fixed solutions was dramatically reduced to only 55.77%. This is obvious since the number of available satellites is significantly reduced, resulting in a significant reduction of the percentage of authenticated fixes (RTK fix under the OSNMA strict settings). Moreover, and as analyzed in [26], the use of cross-authentication in OSNMA can lead to having visible but not authenticated Galileo satellites, which therefore will not take part in the PVT computation. Although to a lesser extent, this can also contribute to the overall satellite visibility reduction when OSNMA is in strict mode. In 16.17% of the strict cases even no PVT solution at all (no-fix) could be achieved, which was most probably due to the reduced number of visible satellites. The probability of an SPP solution was 8.65% for the OSNMA strict case. For the other OSNMA configurations, the probability for an SPP solution was only about half as small (3.72% for OSNMA off, 3.53 for OSNMA loose). These results clearly underline that it is very important to expand the network of authenticated satellites so that the OSNMA service can be used reliably. When considering Figure 4, one can derive that the percentage of RTK fixes increases with the number of satellites. Simultaneously, the percentage of RTK float solutions de  
Figure 3: Proportions of position types. Figure 2: Scheme of the setup for OSNMA performance measurements. creases. The percentage of authenticated fixes (OSNMA strict) is best when 9 to 10 authenticated satellites are available. There were no cases with more then 10 authenticated satellites. More than 10 satellites could only be used by applying the OSNMA off and loose configurations. When further increasing the number of satellites, the percentage of RTK fix solutions improved slightly and the percentage of SPP solutions decreased for both configurations. This can even be seen when increasing the number of satellites from 13-14 to 15-18. The increase in this case accounts for 1.52% in the OSNMA off configuration, and for 2.24% in the loose configuration. Most RTK-fix solutions could be achieved in the OSNMA loose configuration, with a probability of 97.06%. This value displays the performance that can presumably be achieved with the final Galileo OSNMA service. This is a very promising result in view of autonomous driving vehicles. In general, the performance of the receivers with the OSNMA off and loose configurations was very similar, regardless of the number of visible satellites. The localization accuracy was investigated by looking at the distribution of the two-dimensional (horizontal) localization error for the different OSNMA configurations. The left side of Figure 5 shows the Cumulative Distribution Function (CDF) for an open sky case. An autonomous vehicle was driving there, and all three receivers could achieve RTK-fix for the whole time. As can be seen, the 2D localization accuracy was always better than 5 cm.