Toward Accurate Human Tracking: Modeling Time-of-Arrival for Wireless Wearable Sensors in Multipath Environment

For time-of-arrival-(TOA)-based indoor human tracking system, the wireless channel between human body surface and external reference node can be regarded as the source of inaccuracy. Since only the arrival time of direct path provides accurate range estimate, the nonline of sight caused by human body leads to undetectable direct path condition and thus results in a significant distance measurement error. In this paper, we measured TOA ranging error for indoor human tracking applications inside a typical office environment. A large number of TOA ranging samples was obtained and statistically analyzed. The TOA ranging error was modeled as a Gaussian random variable with the parameters, including position of target sensor, angle between human facing direction, and direction of transmitter-receiver, signal-to-noise ratio, and bandwidth of the system. As a validation of proposed model, excellent agreement has been found between empirical measurement and model-based software simulation.