# Performance Analysis of BDS-5G Combined Precise Point Positioning
## 3 Results and Discussion
### Experimental Environment
#### 3.1.2 5G Environment  
As shown in Figure 2, five 5G micro base stations were deployed at the National Time Service Center of the Chinese Academy of Sciences in Xi'an, China. The experimental field was a rectangular area of 30 m \(\times\) 50 m. The frequency of the 5G signal used in the experiment was 3.5 GHz, the bandwidth of the signal was 100 MHz, and the accuracy of time synchronization was greater than 1 ns. Under the local coordinate system, the coordinates of the point to be measured were set to (0, 0, 0) m and the total number of base stations was five. The coordinates of the 5G micro base stations were as follows: base station A (11.851, 11.621, 2.005) m, base station B (\(-\)1.688, 12.198, 2.122) m, base station C (\(-\)1.419, \(-\)3.943, 2.299) m, base station D (\(-\)1.379, \(-\)14.719, 2.283) m, and base station E (12.765, \(-\)14.554, 2.292) m. \begin{table}
\begin{tabular}{c c} \hline \hline
**Items to Be Processed** & **Handling Strategy** \\ \hline BDS 1 observation signal type & Pseudorange and carrier phase observations: BDS B1, B3 \\ Solving mode & PPP2-static/dynamic solving \\ Ambiguity & Float solution \\ Elevation angle & 7\({}^{\circ}\) \\ Sampling interval & 30 s \\ Orbital and clock difference products & IS precise products \\ Ionospheric delay & Dual-frequency ionosphere-free combination, eliminating \\  & first-order terms and ignoring higher-order terms \\  & The dry delay was corrected using the Saastmoinen model and the \\  & wet delay was estimated as a parameter \\  & Absolute antenna phase center model \\ Phase winding, solid tide correction, relativistic effects & Model correction \\  & BDS receiver clock difference \\  & Coordinate constraint method \\  & Recursive least squares parameter estimation \\  & Eliminating outliers in measured data \\  & Parameter estimation \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Data processing strategies. Figure 1: Number of satellites for BeiDou Navigation Satellite System (BDS) involved in the solutions for Scene 1 and Scene 2. In our previous experiments, we tested the positioning performance of 5G base stations in the above environment, in which we compared the positioning accuracy of the measured data and simulated data and investigated the advantages of combined SPP and 5G positioning in the occluded environment. The details of the experiments were described in paper [23]. In order to perform a combined BDS and 5G positioning test, we panned this set of actual 5G TOA data and base stations so that the point to be measured overlapped with the JFNG station and performed the following experiments on the effect of the quantity of 5G micro base stations on the PPP results. With each successive experiment, the quantity of base stations was increased from one to five in the order of ABCDE. In Scene 1, as the quantity of 5G base stations increased, the position dilution of precision (PDOP) values decreased, with a 11.29% decrease for the case with five base stations compared with the case without base stations (Table 2). In Scene 2, the contribution of 5G base stations to the PDOP value was more obvious; compared with the PDOP value without base stations, the PDOP value of the five base stations decreased by 17.55%. In addition, in order to simulate the effect of different geometrical configurations of base station deployment on PPP, we simulated four sets of base station combinations with different geometrical configurations (Figure 3): Groups A, B, C, and D. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Number of 5G Base Stations** & **Scene 1** & **Scene 2** \\ \hline
0 & 0.8390 & 1.1422 \\
2 & 0.8124 & 1.0386 \\
3 & 0.7815 & 1.0216 \\
4 & 0.7693 & 0.9602 \\
5 & 0.7443 & 0.9418 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Position dilution of precision (PDOP) for different numbers of fifth generation mobile communication technology (5G) base stations in two scenes. Figure 2: Different numbers of fifth generation mobile communication technology (5G) base stations.