Indoor positioning can be considered as a blank area for applications, and there is no very suitable technology to achieve this function. GPS indoor signals are poor, and RSSI positioning is limited by accuracy and range, and it is difficult to provide satisfactory services. The recent release of Bluetooth 5.1 has brought a new direction-finding function, which can provide centimeter-level positioning accuracy, and provides a more reliable technical solution for indoor positioning.
How to achieve the “centimeter-level” positioning of Bluetooth 5.1?
After the introduction of the Direction Finding in the Bluetooth 5.1 core specification, the positioning accuracy of Bluetooth can be optimized to “centimeter-level”. This is because the direction-finding function of Bluetooth 5.1 is mainly composed of two positioning elements, namely the AoA (Angle of Arrival) and the AoD (Angle of Departure).
The AoA is a technique to obtain the azimuth and distance of the transmitter and the receiver by triangulation by testing the direction of arrival of the signals approaching the receiver, mainly for RTLS (real-time positioning system), item tracking and landmark information. The directed device uses a single antenna to transmit a specific set of direction-finding packets, and the receiving device has multiple antennas. Different antennas of the receiving device will have a small time offset when receiving the direction-finding packet of the positioning device. This phase shift caused by the side packet signal on the receiving device antenna is called the IQ samples of the signal. Then analyze the IQ value to obtain the precise coordinate information of the device to be located.
The AoD is also the use of signal phase difference technology, its triangulation is performed by testing the direction of departure of the signals transmitting from the transmitter, mainly for indoor positioning systems. This direction-finding technology is suitable for indoor item management, logistics, and storage. The positioning host sends a set of direction-finding packets through the multi-antenna array, and the positioning device receives the direction-finding packet and calculates the coordinates of the positioned device through the sampling and analysis of IQ values.
Combining the AoA and AoD methods, the positioning accuracy of Bluetooth 5.1 has reached the centimeter level, and can even achieve indoor 3D positioning.
Does this article guide you out of the mist of how Bluetooth 5.1 implements centimeter-level positioning? If not, don’t hesitate to contact Feasycom for more information.
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Image source: Silicon Labs