CDMA handoff arrangement for mobile station encountering sudden field strength variations at the boundary of adjacent cells

摘要

A CDMA base station comprises a convolutional encoder (141) for encoding signals from a base station controller and feeds a variable gain amplifier (142), the signals including a first or a second control message multiplexed with a user signal on a traffic channel assigned to a mobile station. The first control message indicates that a soft handoff operation is initiated and the second control message indicates that the soft handoff operation is being terminated. A control message detector (143) is used to control the variable gain amplifier (142) when the first control message is being encoded by the convolutional encoder so that the gain of the first control message is higher than that of the user signal. A transmitter (150) produces a spread spectrum signal from the output of the amplifier (142) for transmission to the mobile station. As a result, the first control message is transmitted at a power level sufficient to reach the mobile station, which would otherwise fail to receive this message when it encounters a sharp decrease in field intensity. IMAGE