With thepopularity of smartphones and the development of mobile Internet, map and navigation softwarewill enter a new era - indoor navigation. For example, in a large shoppingmall, use indoor navigation to quickly find exits and elevators. The houseopens or closes the lights according to your location. The store pushes moreinformation about the products according to the user's specific location.

Bluetooth positioning is performed by measuring signal strength. This is ashort-range, low-power wireless transmission technology that installsappropriate Bluetooth LAN access points indoors, configures the network into amulti-user based network connection mode, and ensures that the Bluetooth LANaccess point is always the piconet. The (piconet) master device can obtain theuser's location information. Bluetooth technology is primarily used forsmall-scale positioning, such as single-story halls or warehouses. The biggestadvantage of Bluetooth indoor positioning technology is that it is small insize and easy to integrate in PDA, PC and mobile phone, so it is easy topopularize. In theory, for a user holding a Bluetooth-enabled mobile terminaldevice, the Bluetooth indoor positioning system can determine the position ofthe device as long as the Bluetooth function of the device is turned on. Whenthis technology is used for indoor short-distance positioning, the device iseasily found and the signal transmission is not affected by the line of sight.

The process of positioning principle is shown in the figure below: A and B aretwo known coordinate points, using RSSI and distance calculation formula

D = 10^((abs(RSSI)-A)/(10*n)

The straight line distance from A and B can be measured, and the position ofthe measuring point C can be calculated by a mathematical formula.