Energy-aware pedestrian trajectory system

RF-based positioning is the most popular positioning technology for indoor environments due to the wide deployment of WLAN. However, RF-based solutions suffer from the drifting problem. In this work, an Inertial Measurement Unit (IMU) based Pedestrian Trajectory System (abbreviated as PTS) that can assist in alleviating the drifting problem is proposed to depict pedestrian trajectories. The proposed system is composed of Stepping Aware Module (SAM), Stride Length Module (SLM) and Walking Direction Module (WDM). Based on the information obtained from the three modules including the stride length and walking direction of each step, the pedestrian trajectory can be depicted by dead reckoning. Since smart phones are the target platform of the application, energy consumption is an important consideration. To understand the energy consumption of the built-in IMU, the energy consumption of various embedded subsystems of smart phones including the GPS, WiFi, 3G, Bluetooth and IMU is measured. Compared to other subsystems, the energy consumption of the IMU subsystem should not be ignorable. Since the sampling rate of the IMU is a major factor affecting the energy consumption, we implement the proposed PTS under a lower sampling rate 20 Hz instead of 40 Hz. Our experiment results show that there is no significant performance difference between sampling rate 20 Hz and 40 Hz. By this means, the lifetime of the smart phones between each charge can be prolonged.