Access control system and access control method using the same

A sub-reader device communicating with a reader device such that the reader device communicating using first communication protocol communicates with first device communicating using second communication protocol different from the first communication protocol via the sub-reader device, wherein the second communication protocol is not supported by the reader device, the sub-reader device comprising:

• a processor configured to obtain first request information using the second communication protocol from the first device, obtain second request information based on the first request information, and provide the second request information to the reader device using the first communication protocol,
• wherein the sub-reader device authenticates the first request information based on first information,
• wherein the first information is obtained from a server or pre-stored in the sub-reader device,
• wherein the second request information is provided to the reader device when the first request information is authenticated, and
• wherein the sub-reader device obtains the first request information when the first device receives information related to the first request information from the server.