Asynchronous time-based indoor localization systems—Comparative analysis under realistic industrial-oriented conditions

The growing need for accurate localization in increasingly interconnected industrial environments has driven research towards developing new indoor localization systems. This work analyzes and compares three asynchronous localization methods based on the Two-Way-Ranging (TWR) protocol: Single-Sided TWR (SS-TWR), Symmetric Double-Sided TWR (SDS-TWR), and Alternative Double-Sided TWR (AltDS-TWR) in addition to the Asynchronous Time Difference of Arrival (A-TDOA) system. Similar comparisons have been previously reported, however, these only take into consideration clock-associated errors and unrealistic test conditions, thus overlooking the impact of signal paths required by each method, therefore reaching conclusions far from those expected in real applications. In this paper, we propose a more complete and fair comparison among these four asynchronous systems. For this purpose, we propose a clock, noise, and multipath error characterization for each localization system to perform a realistic comparison over multiple industrial scenarios where Autonomous Mobile Robots freely navigate. In order to ensure a fair comparison, a sensor distribution optimization has been carried out for attaining the best achievable performance of each analyzed system. Results show that the selection of the best localization system may depend on the scenario and application conditions as well as the deployment budget. Nevertheless, results from the AltDS-TWR method highlight the potential of this system, yet further research should be conducted to verify the influence of moving targets for this TWR method.