Acoustic Indoor Localization Using Two Base Stations Based on TDoA and Relative Speed to Base Stations

To achieve 2-D localization using only the Time Difference of Arrival (TDoA) measurements, a minimum of three base stations is required. To further reduce the number of base stations needed for positioning, this study proposes, for the first time, a novel method that combines TDoA and relative speed to base stations (RStBSs) to locate the targets, reducing the minimum number of base stations required by one compared to methods that rely solely on TDoA. The proposed method transforms the coordinate system, constructs a system of equations for the target position in the transformed coordinate system, and solves these equations to determine the target position. The algorithm then substitutes the two types of measurements, TDoA and RStBS, into these equations to estimate the target position. The simulation results indicate that the algorithm achieved a positioning accuracy better than 1.0 m (75%) without cumulative error when the standard deviation of the measurement noise was less than 0.3 m. In the two-base-station acoustic indoor positioning experiment, a permanent magnetic block was utilized to determine the initial position of the target, and the TDoA and RStBS measurements were calculated by estimating the audio arrival time (AAT). The experimental results indicate that the target positions estimated by the proposed method closely align with the actual motion trajectory, particularly when fused with conventional pure TDoA localization, thereby confirming its effectiveness in real-time target tracking. Furthermore, integrating this approach with acoustic NLOS identification techniques is expected to significantly enhance the robustness and practical utility of acoustic indoor positioning systems in complex environments.