Power control device and method for mobile communication system

PURPOSE: A power control device for a mobile communication system is provided to control power while a traffic channel is off. CONSTITUTION: A power control device for a mobile communication system includes a base station and a mobile station. The base station has a transmission diversity function, generates a specific common channel signal for transmitting a traffic channel signal through a traffic-on antenna, and transmitting a reference value about a transmission power through a traffic-off antenna. The mobile station has a plurality of receivers according to transmission diversity. After the receivers store traffic power in case of a traffic-off, the mobile station detects a power variation of a common channel, calculates a virtual traffic power, generates virtual power control information according to the virtual traffic power, and transmits the virtual power control information to the base station through a backward link.