## 3 Results
### Velocity Domain Results
configuration for almost all the figures of merit. The Glonass-only performance is deficient for both the uBlox and Xiaomi devices. From the tables considering the GPS Novatel case, it can be noted that the rms horizontal and vertical errors are 2 cm/s and 3.6 cm/s, respectively, for Doppler and 2 mm/s and 4 mm/s for TDCP; the maximum errors are 7.2 cm/s and 11.7 cm/s for Doppler and 17 mm/s and 55 mm/s for TDCP. For the uBlox case, the rms errors are at the cm/s level for both the Doppler and TDCP cases. For the TDCP case, larger maximum horizontal and vertical errors of about 1 m/s and 1.8 m/s, respectively, have been observed. Finally, for the smartphone case, Doppler-based performance is good, considering that the horizontal and vertical rms errors are 1.3 cm/s and 4.5 cm/s, comparable with the Novatel case. In Table 6, the solution availability values for the different configurations are reported. Solution availability is defined as the percentage of available solutions when the number of available measurements is at least four. Herein, a measurement is considered available if it comes from a satellite at an elevation angle above 15 degrees and if it has a C/N0 above 25 dB-Hz. Moreover, in the epochs where the geometry is too poor, specifically with 3D-DOP larger than 15, the solutions are considered not available. TDCP solution availability cannot be 100%, because two consecutive CP measurements should be differenced to obtain a TDCP measurement, and so it is not possible to have TDCP measurements in the first epoch. From Table 6, it is evident that for the GPS case, the solution availability is very close to 100% for both the Doppler shift and the TDCP case. For the BeiDou case, it can be noted that few solutions are not available for Xiaomi. The situation for Glonass and Galileo is strongly dependent on the type of receiver. Using uBlox in both cases, the solution availability is very high, about 95% for Glonass and about 100% for Galileo; only marginal differences can be appreciated between the Doppler shift and the TDCP case. The situation is completely different when the smartphone solutions are considered: for the Glonass case, the solution availability using Doppler shift measurements is around 50%; this value is reduced in the TDCP case to about 43%. For Galileo, the Doppler shift solution availability is about 42%, and it was not possible to compute the TDCP solution; hence, the solution availability in this case is 0%. Hence, the configurations characterized by the worst solution availability are Glonass-only and Galileo-only with Xiaomi with a percentage of about 50 or lower, and with the TDCP solution never being possible for Galileo-only. From the errors reported in Tables 4 and 5 and Figures 7 and 8, the presence of anomalous measurements leading to large velocity errors is evident, above all for the TDCP solution and non-high-grade devices. In this context, the application of RAIM-FDE can be effective in improving the results. In Figures 9 and 10 and Tables 7 and 8, the same error analysis carried out previously is reported, but with the application of the Subset algorithm. RAIM-FDE evaluates the consistency of the measurements, tries to reject blunders, and indicates reliable solutions. In this error analysis, only reliable solutions are considered. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **Novatel** & **uBlox** & **Xiaomi** \\ \hline \multicolumn{5}{c}{**(\%)**} & **(\%)** & **(\%)** & **(\%)** \\ \hline \multirow{3}{*}{**GPS**} & Doppler & 100.00 & 100.00 & 100.00 \\  & TDCP & 99.97 & 99.97 & 99.97 \\ \hline \multirow{3}{*}{**GLO**} & Doppler & - & 94.79 & 50.32 \\  & TDCP & - & 94.27 & 42.74 \\ \hline \multirow{3}{*}{**GAL**} & Doppler & - & 100.00 & 41.93 \\  & TDCP & - & 99.97 & 0.00 \\ \hline \multirow{3}{*}{**BDS**} & Doppler & - & 100.00 & 99.94 \\  & TDCP & - & 99.97 & 99.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Solution availability for single devices and single GNSSs.