# Evaluation of 5G Positioning Performance Based on UTDoA, AoA and Base-Station Selective Exclusion
## 4 Simulation Results and Evaluation
### Performance Results
When the values of \(\text{k}_{\phi}\) and \(\text{k}_{\theta}\) are very small, the HDOP tends to be equal to the one of TDoA and vice versa. For the case of AoA, the HDOP values are also associated with the size of the deployment area of the positioning system. This is reflected in the small values of the HDOP of AoA, meaning that the BSs are deployed closer in distance. The positioning accuracy is now evaluated by assessing the actual gain that is obtained in terms of the UE positioning performance. In conditions of synchronization error, with the presence of NLoS and multipath, UTDoA leads to a poor accuracy and reliability of the computation position. This is reflected in the simulation results for both scenarios shown in Figures 5 and 6, where severe degradation errors are clearly seen compared to what is expected in ideal conditions (see Figures 7 and 8). The combination of angle observables  
Figure 3: Simulation scenario. with those of time delay has already been shown to provide a significant improvement with UTDoA solutions, where the positioning accuracy is less than 30 m for 80% of the UEs. The maximum horizontal position error is reduced by 27.5%. However, this improvement does not overtake the performance achieved by RTT, which relaxes the constrained positioning problem, i.e., the presence of synchronization error giving a position accuracy improvement of 5%. This can be noticed above the 80 th percentile in Figures 5 and 6. Since there is a predominance of NLoS conditions in 5G urban transmissions, the BS selective solution is of high interest for its ability to eliminate such impairments, in order to achieve a better performance assessment under realistic assumptions while using 5G positioning signals. We therefore analyze the impact of BS exclusion mechanism on the joint UTDoA-AoA positioning performance. The probability of false alarm is set to \(\mathrm{P_{fa}}=0.1\), resulting in a threshold of \(\gamma=1.4797\) m for scenario 1 and \(\gamma=1.4879\) m for scenario 2, calculated as explained in Section 3.3.2. Results show a significantly improved hybrid solution when the NLoS exclusion mechanism is applied. The maximum horizontal position error is reduced by 40% compared with the results achieved using UTDoA as the stand-alone technology. The use of this mechanism has improved the accuracy of the hybrid method of 18.51%. It also overcomes the performance achieved using RTT and tends to reach the performance of hybrid solution in conditions of perfect synchronization with an improvement of 12.5%. Another observation related to the performance of the positioning methods is the significant improvement in accuracy until the 30% percentile for the first scenario (see dashed circle). This is explained by the presence of more than one LoS angle measurements in the computation solution and ranging measurements in LoS conditions. Apart from the statistical performance of each method, it is also important to assess the actual gain we obtain through the BS exclusion mechanism in terms of UE positioning performance. The results have shown that it has only met the regulatory requirements for emergency services, i.e., having an accuracy of <50 m on 80% of the cases. However, the use of this method enhances the positioning availability. Table 2 compares the performance of the NLoS monitoring method for both scenarios. From all the BSs that contributed to the positioning computation, 81.86% of them have a synchronization error of \(-50\) ns or \(50\) ns, and from which 38.75% of the cases, in the group of BSs dedicated for the positioning of each receiver, there is one BS with synchronization error. For 43.11% of the cases, more than one BS has a synchronization error. Only 18.14% of the BSs has perfect synchronization. Having a low \(\mathrm{P_{fa}}\), we are expecting that the probability of detecting the faulty BS is high. Figure 4: CDF of the HDOP for UTDoA, AoA and hybrid solution. S1 refers to first scenario and S2 refers to the second scenario.