Objectives Like all radio signals, 5G(5th generation) signal will also face the problem of being vulnerable to transmission interference in complex environments, which will lead to few number of observable base stations, and then affect the performance of positioning. Therefore, it is important to solve the problem of poor accuracy or inability to positioning using only TOA(time of arrived) based 5G positioning in case of signal blockage.
Methods We applied AOD(angle of departure) capability of multi-antenna to 5G positioning, and integrated it with SINS(strapdown inertial navigation system) through EKF(extended Kalman filter) to form TOA/AOD based 5G/SINS integrated navigation system. After that, simulation experiments were designed for two scenarios: With sufficient number of observable 5G base stations and with signal blockage, and the position errors of four methods are compared, these are TOA based 5G positioning, TOA/AOD based 5G positioning, TOA based integrated navigation, TOA/AOD based integrated navigation.
Results Simulation experimental results show that: (1) When the number of observable 5G base stations is sufficient, the addition of AOD reduces the horizontal and vertical position errors, and due to the higher accuracy of the elevation angle, the reduction of the vertical position error is more obvious. (2) When the number of observable 5G base stations is sufficient, compared with 5G positioning, the position error obtained by the integrated navigation is reduced by about 40% in the horizontal direction. However, the TOA based 5G positioning in our experiment has a continuous large error in the vertical direction, which also causes a large vertical error in TOA based integrated navigation. (3) In case of signal blockage, due to the insufficient number of observable 5G base stations, TOA based 5G positioning cannot be performed, but the percentage of successful epochs for TOA/AOD based 5G positioning reaches 98%.And after adding inertial sensors, TOA/AOD based 5G/SINS integrated navigation ensure a 100% positioning success rate, and reduce the position error by 40% to 70%.
Conclusions The addition of AOD can effectively improve the positioning success rate in case of signal blockage. And compared to 5G positioning, integrated navigation can suppress the occurrence of some large position errors, and reduce the horizontal and vertical position errors by 40% to 70%. However, continuous large error in 5G positioning will also affect the results of integrated navigation. Therefore, in a complex environment, fusing AOD capability for integrated navigation can give full play to the advantages of both, improve positioning accuracy and positioning ability, and effectively reduce the probability of the divergence of integrated navigation.
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