Access control system and method for operating an access control system

System for controlling access to a restricted-access zone in a building in which a security gate separates the restricted-access zone from a public zone, comprising:

• radio devices which are each arranged at respective locations at specified distances from the security gate and define a monitoring area, wherein the radio devices are configured for radio communication with wireless devices that are within radio range and assigned to users, wherein a first wireless device at a position (P) of a first user has a respective distance (di), to each of the respective radio devices;
• a control device which is communicatively coupled to a building device,
• a data storage device in which processing instructions for situation-specific calibration modes are stored;
• and
• a signal processing device which is communicatively coupled to the data storage device, the radio devices, and the control device, wherein the signal processing device is configured to analyze the radio communication in the monitoring area and to determine at least one situation indicator therefrom, which indicates a radio situation prevailing in the monitoring area;
• to acquire, for each radio device, a received signal field strength indicator (RSSIi) based on a radio communication with the first wireless device;
• to select the calibration mode assigned to the at least one situation indicator and to read the processing instructions assigned to the selected calibration mode from the data storage device;
• and
• to determine a current position (P′) of the first wireless device as a function of the detected indicators for the received signal field strengths (RSSIi) according to the processing instructions that have been read;
• wherein an individual identifier of the first wireless device is also stored in the data storage device and the individual identifier is transmitted by the first wireless device;
• wherein the signal processing device is configured to feed a control signal to the control device when based on the identifier and the determined current position (P′) of the wireless device a defined rule is satisfied;
• and
• wherein the control device is configured to initiate a building action corresponding to the defined rule, in particular to release the security gate.