BLE positioning technology refers to the use of BLE as a signal source to achieve positioning function, which can be divided into four categories according to the difference in its positioning methods. Category 1: Bluetooth AOA AOD positioningBluetooth 51. The standard introduces the angle positioning algorithm of AOA and AOD, which senses the arrival and transmission direction of the transmitting node signal through the Bluetooth device, calculates the relative orientation or angle between the receiving node and the transmitting node, and the positioning accuracy achieves sub-meter level. 
AOA and AOD technology schematic diagram AOA uses a single antenna to transmit a direction-finding signal, and the receiving terminal has a built-in antenna array, when the signal passes, the phase difference will be generated due to the different distances received by the array antenna, and then the direction of the signal is calculated. AOD, on the other hand, transmits signals from a device with an array antenna to a single antenna terminal, and the receiving terminal can calculate the direction of the wave through the received signal to achieve positioning. The second category: Bluetooth beacon positioningBluetooth Beacon is based on RSSI (signal strength) positioning, different from the single base station positioning of the gateway, the solution of Bluetooth Beacon is three-sided positioning, that is, through the three (or more) base stations to calculate more accurate location information, the accuracy range is between 3m-5m. Category 3: Consumer point-to-point positioning productsThe so-called point-to-point positioning product refers to the mobile phone as the core, no need to arrange the positioning network, only the positioning product needs to be connected with the mobile phone. Its positioning principle includes Bluetooth RSSI and AOA, because RSSI and AOA are basically the standard configuration of Bluetooth chips, specific to whether the product has AOA, the most important thing is to see whether there is an AOA antenna. The most representative of the point-to-point Bluetooth positioning scenario with mobile phones as the core is the missing object tag and car key. Category 4: Bluetooth gateway room-level positioningThat is, the core device is a Bluetooth gateway, which can be used to achieve room-level positioning through the Bluetooth gateway combined with RSSI, which is very suitable for asset management scenarios. Because the general enterprise inventory or important asset management only needs to achieve room-level accuracy, and if the number of devices to be managed is not particularly large, the use of Bluetooth gateway positioning is the lowest cost solution. According to our research, BLE also has a fifth type of positioning technology, and its standard is expected to be officially released in the next few years, and this article also previews it in advance:Category 5: Bluetooth channel soundingBLE CS provides a Phase Based Ranging (PBR) solution, which is mainly used for high accuracy distance measurements (HADM) between two BLE devices. 
Add ** annotations, no more than 140 words (optional) on frequency F, the PBR measures the distance by the phase shift when propagating at the distance D. When two or more signals of different frequencies are used, the distance can be measured by measuring the phase difference between the signals. When the distance is estimated using channel sounding, one device initiator and the second device repeats the signal transmission (reflector) without modifying the phase. For each transmission with a frequency of fi, the initiator measures the phase change between the transmitted and received signals. Uncoded narrowband constant-packet signals can be sent or received using a single antenna to support standard Bluetooth Low Energy chips.