Transmit power control method for radio communication system and radio base station device

A base station device for making radio communications with one or a plurality of mobile stations, comprising:

• a transmitter module for sending a pilot signal;
• a holding module for holding a criterion value indicating a target channel quality value for mobile stations within a communication range of the base station;
• a storage for creating quality data based on received power reports of the pilot signals received by the mobile station or mobile stations and storing the quality data;
• a transmit power determination module for creating a first representative value indicating average channel quality for the mobile station or mobile stations from the stored quality data and determining transmit power depending on a result of comparison between the first representative value and the criterion value;
• and
• a criterion value updating module for creating a second representative value indicating distribution of low channel quality and updating the criterion value depending on a result of comparison between the second representative value for mobile station quality data and the criterion value.