Access control system and access control method using the same

An access control method of a user terminal that communicates with a door operating device controls whether a door is to open of not, the access control method comprising:

• receiving a first signal from the door operating device;
• determining whether to transmit open authentication information to the door operating device based on the first signal;
• determining a distance between the door operating device and the user terminal based on a received signal strength corresponding to a received signal from the door operating device;
• determining whether the distance between the door operating device and the user terminal is within a first distance;
• and
• transmitting the open authentication information to the door operating device when it is determined to transmit the open authentication information to the door operating device and the distance between the door operating device and the user terminal is within the first distance such that the door operating device determines whether the door is to open or not based on the open authentication information;
• wherein the open authentication information includes at least one of identification information of the user terminal and identification information of a user of the user terminal such that the door operating device determines whether the door is to open or not based on the at least one of the identification information of the user terminal and the identification information of the user of the user terminal included in the open authentication information.