Patent ID: 6847624

Claim:
A CDMA mobile communication system, in which when a plurality of mobile stations access a base station using a common channel at arbitrary timings, each mobile station transmits a preamble for notifying the base station of an occurrence of a message before actually transmitting the message, and the base station compares, in response to reception of the preamble, a received level of the preamble with a predetermined threshold value for making a decision on whether to authorize the mobile station to transmit the message or not, and transmits a transmission control signal for controlling message transmission to the mobile station in accordance with a compared result, said CDMA mobile communications system comprising: measuring means for measuring a signal-to-interference power ratio after RAKE combining when the base station receives the preamble transmitted from the mobile station; comparing means for comparing the signal-to-interference power ratio with the predetermined threshold value for deciding on whether to authorize the message transmission or not; and control means for transmitting the transmission control signal authorizing the message transmission when said comparing means decides that the measured signal-to-interference power ratio is equal to or greater than the predetermined threshold value, and for inhibiting transmission of the transmission control signal authorizing the message transmission when said comparing means decides that the measured signal-to-interference power ratio is less than the predetermined threshold value.