BleHe: Indoor Positioning Using a Single BLE Base Station with Height Correction
Hanying Zou, Dan Xia, Xiaolong Zheng, Liang Liu, Huadóng Ma · 2024
The Bluetooth 5.1 specification introduces the Angle of Arrival feature, which significantly enhances its applications in indoor positioning. Given the height of the target, a single BLE (Bluetooth Low Energy) base station can locate the target, thereby reducing deployment costs. However, existing methods often assume that the target's height is known in advance and remains constant, which is not always true in practice. The height can vary significantly due to user posture changes, such as when picking up a phone from a pocket, leading to positioning errors. In this paper, we propose BleHe, a novel indoor positioning system that incorporates height correction to enhance positioning accuracy in scenarios with dynamic height changes. BleHe detects height changes by utilizing on-device IMU sensor and subsequently notifies the base station of any detected height change events. To avoid altering the commodity Bluetooth protocols, rather than directly modifying application data, we create a side channel to delivery the height change information from the device to the base station by adjusting the BLE packet transmission frequency. This method allows the base station to infer the start and end times of height changes and subsequently refine the target's trajectory using a height-aware particle filtering-based positioning correction method that we propose. Experimental results demonstrate that BleHe achieves an average positioning error of 34.4cm, even in scenarios involving posture changes during walking.