PURPOSE: To provide a communication system where a base station can be effectively scanned by a mobile station in the mobile communication.

CONSTITUTION: The base stations 100, 200 and 300 perform the communication in a multi-carrier system where plural carriers of different levels of frequency are simultaneously transmitted through a single transmission channel. Then a mobile station 400 performs the communication with optional one of stations 100, 200 and 300. In such a communication system, the stations 100 to 300 transmit the known signals through a specific common transmission channel synchronously with each other and with every assigned timing.