Wi-Fi Azimuth and Position Tracking: Signal Propagation, Modeling and Evaluation

Tracking algorithms for estimating and tracking the azimuth angle regarding north and a two-dimensional position of a mobile unit carried by a pedestrian are presented. Outdoors, the azimuth angle of a device can be easily detected using an electronic compass. The position can be calculated using a global navigation satellite system. Indoors, magnetic disturbances lead to unreliable compass outputs. Also, indoors there exists no standard positioning system. Using Wi-Fi signal strength measurements the position of a receiver can be tracked using so called fingerprinting methods. If the signal strengths measurements are collected with directional antennas additionally the azimuth can be tracked. For the presented tracking filters we extended Wi-Fi based Markov localization algorithms for evaluating directional antennas to calculate azimuth besides position. Furthermore, these techniques have been adapted to use a particle filter for the estimation. Well known Wi-Fi fingerprinting approaches are included in the measurement models and pedestrian dead reckoning in the prediction models. Measurements have been collected inside and outside of an office building to evaluate the performance of the different tracking algorithms. Especially in indoor environments these approaches facilitate the use of electronic guides that offer additional information by means of augmented reality, e.g. on museum exhibits in visual range.