Calibration-Free Positioning Technique Using Wi-Fi Ranging and Built-In Sensors of Mobile Devices

As positioning solutions integrate multiple components to improve accuracy, the number of parameters that require calibration has increased. This article studies a calibration-free positioning technique using Wi-Fi ranging and pedestrian dead reckoning (PDR), where every parameter in the system is optimized in real time. This significantly decreases the time and effort required to perform manual calibration procedures and enables the positioning solution to achieve robust performance in various situations. Additionally, this article studies an efficient way of performing irregular Wi-Fi ranging procedures to improve battery life and network performance of mobile devices. The positioning performance of the proposed method was verified using a real-time Android application on several mobile devices under a large indoor office environment. Without any calibration, the proposed method achieved up to 1.38-m average positioning accuracy for received signal strength (RSS)-based ranging scenarios, which differs only by 30 cm from the benchmark assuming perfect calibration. In addition, the proposed method achieved up to 1.04-m accuracy for round trip time (RTT)-based ranging scenarios with a 40-MHz bandwidth configuration, which differs only by 10 cm from the benchmark.