A radio communication system, comprising a control station and a subsidiary station that perform time-division multiplex communication, wherein the control station comprises: a first radio section that is configured to perform radio communication with the subsidiary station and to transmit a first control signal to the subsidiary station; and a first control section that is configured to determine a first sync word according to a predetermined method and to control the first radio section to transmit the first control signal including the first sync word, the subsidiary station comprises: a second radio section that is configured to perform radio communication with the control station and to receive the first control signal from the control station; and a second control section that is configured to detect the first sync word from the control signal, to establishe synchronization with the control station based on the first sync word, and to control the second radio section to perform time-division multiplex communication with the control station, characterized in that the first control section is configured to control the first radio section to transmit a second control signal including a fixed second sync word common to the control signal in the radio communication system, and the second control section is configured to establish, when the first sync word is not detected from the first control signal, synchronization with the control station by using the second sync word included in the second control signal. a first radio section that is configured to perform radio communication with the subsidiary station and to transmit a first control signal to the subsidiary station; and a first control section that is configured to determine a first sync word according to a predetermined method and to control the first radio section to transmit the first control signal including the first sync word, the subsidiary station comprises: a second radio section that is configured to perform radio communication with the control station and to receive the first control signal from the control station; and a second control section that is configured to detect the first sync word from the control signal, to establishe synchronization with the control station based on the first sync word, and to control the second radio section to perform time-division multiplex communication with the control station, characterized in that the first control section is configured to control the first radio section to transmit a second control signal including a fixed second sync word common to the control signal in the radio communication system, and the second control section is configured to establish, when the first sync word is not detected from the first control signal, synchronization with the control station by using the second sync word included in the second control signal. a second radio section that is configured to perform radio communication with the control station and to receive the first control signal from the control station; and a second control section that is configured to detect the first sync word from the control signal, to establishe synchronization with the control station based on the first sync word, and to control the second radio section to perform time-division multiplex communication with the control station, characterized in that the first control section is configured to control the first radio section to transmit a second control signal including a fixed second sync word common to the control signal in the radio communication system, and the second control section is configured to establish, when the first sync word is not detected from the first control signal, synchronization with the control station by using the second sync word included in the second control signal.