The disclosed embodiments include computer-implemented devices, systems, and methods that determine a position of a terminal device within a communications environment. In one embodiment, a positioning device may include a memory and one or more processors. The one or more processors may be configured to change a variable to be transmitted to a user device, to store the changed variable in the memory, and to output a first signal indicating that the user device is present in a predetermined area, based on a first variable received from the user device and the changed variable stored in the memory.