In a communication system, a mobile device receives a FCMC signal from the immobile device upon entering a communication service area of the immobile device. The mobile device checks for a coincidence of its own link identification code with other link identification codes included in the FCMC signal and already being used for communication with other mobile devices in the same communication service area. If the coincidence is present, the mobile device changes the own link identification code so that the communication with the immobile device may be executed by using the changed link identification code. In the event that a plurality of mobile devices use the same link identification codes, the immobile device requests the mobile devices to change the same link identification code to different-ones among the mobile devices. |