Loosely-coupled IR-UWB handset and ankle-mounted inertial unit for indoor navigation

In this paper, we address the indoor pedestrian tracking problem by combining an Impulse Radio - Ultra Wideband (IR-UWB) handset with a foot-mounted Inertial Measurement Unit (IMU), including an accelerometer and a gyroscope. A new quality indicator is provided as a function of the Signal to Noise Ratio (SNR) for energy-based Time Of Arrival (TOA) estimators, enabling outliers detection and measurements covariance scaling before fusion. Then the radio and inertial modalities are loosely coupled within a specific and stable Extended Kalman Filter (EKF), where inertial data control state predictions whereas Combined Time Differences Of Arrival (CTDOAs) are formed as low dimension observations. Experimental results are presented herein, emphasizing the complementarity of the two technologies, as well as the relevance of the proposed fusion strategy.