| 摘要 |
PROBLEM TO BE SOLVED: To avoid momentary interruption of voice or data in a communication mode by establishing synchronization between a base station under communication and its adjacent base station during transmission or non-transmission of an idle slot of a resident or non-resident carrier and receiving a hand-off command from the base station under communication to start radio communication with the adjacent base station. SOLUTION: When a mobile station 13 gets out of a zone 11a of a base station 11, the receiving level of the station 11 is detected by a resident carrier NSC of a frequency f2. When the receiving level of the station 11 is lowered than its standard level, the receiving level of an adjacent base station 12 is detected in a non- transmission state of an idle slot of the station 11. When the receiving level of the station 12 is lower than its standard level, the station 13 establishes synchronization with the station 12 and switches the communication carrier from the carrier NSC of frequency f4 of the station 12 to a non-resident carrier CC of frequency f2 of the station 11. Then the station 13 restarts the communication with the station 11, receives a hand-off command from the station 11 and switches the communication carrier from the carrier CC of the station 11 to the carrier NSC of the station 12 to perform an hand-off operation.
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