| 摘要 |
PROBLEM TO BE SOLVED: To enhance the utilizing efficiency of a radio channel in a cellular communication system of a CDMA format. SOLUTION: In the branch control system, a mobile unit 11 enters a simultaneous communication states with 1st-3rd base stations when the mobile unit 11 is resident in a position where cells 14-18 are overlapped. In this state, a control section in the mobile unit 11 detects a frame error rate and a reception level or the like from a received signal during communication with each base station and compares them with reference values stored in the mobile unit 11. Upon detecting a base station whose reception state is poor, the control section starts open processing of communications with a corresponding base station and transmits an open request to each base station. Each base station transmits the received open request to a base station controller 12. The base station controller 12 receiving the request transmits an open request acknowledgement to delete communications between the base station and the mobile unit 11 to each base station and each base station transmits a received open request acknowledgement to the mobile unit 11 in a radio signal. Then the concerned base station and the mobile unit 11 stop their communications after conducting a predetermined procedure.
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