Base Station Selection Method for RAT-Dependent TDOA Positioning in Mobile Network

There are several methods available for the positioning of mobile devices, such as GNSS, Wi-Fi, Bluetooth and radio access technology (RAT) dependent methods. Among them, the RAT-dependent positioning method uses only measurement information from the mobile network so that devices do not need to be equipped with receivers for GNSS, Wi-Fi or other systems. This can lead to device simplification and power savings. In this paper, we consider the time difference of arrival (TDOA) positioning method, which is a typical RAT-dependent positioning method. The positioning accuracy of the TDOA positioning method depends on which 4 base stations (BSs) are selected. For mobile network TDOA positioning, one method is to select BSs near the mobile device. However, if two or more BSs of the selected 4 BSs are near each other, the positioning accuracy is reduced. Another BS selection method is to select BSs so that the tetrahedron volume determined by connecting the positions of the 4 BSs is large. However, in this method, the BSs far from the mobile device are likely selected, so the elevation angles between all 4 selected BSs and the mobile device are small. In this case, the positioning accuracy is also low. Therefore, we propose a BS selection method in which at least one of the BSs has a large elevation angle while maximizing the volume of the tetrahedron formed with the positions of the 4 BSs, and evaluate the effectiveness of the proposed method in terms of positioning accuracy.