Base station, mobile communication system and radio signal quality measurement method

A mobile communication system comprising a mobile station and a base station, wherein

• the base station comprises:
• a received signal power measurement unit that calculates a radio signal power of a radio signal received from the mobile station which is connected by radio connection;
• a measurement period decision unit that determines whether or not a transmission rate change is expected to occur based on a first index representing a transmission rate of received data transmitted from the mobile station and one of a second index representing a resource assigned to the mobile station and a third index representing an amount of data buffered in the mobile station and to be transmitted, sets a measurement period which is to be used for calculating an interference power to a first length when a period in which the transmission rate change is expected not to occur exceeds a certain period and sets the measurement period to a second length shorter than the first length when the transmission rate change is expected to occur;
• an interference power measurement unit that calculates interference power by averaging power of interference wave over the measurement period;
• a received signal quality measurement unit that calculates signal quality of the radio signal received from the mobile station based on the radio signal power and the interference power;
• and
• a transmission power decision unit that decides a transmission power control value to the mobile station so as to cause the mobile station to increase the transmission value when the signal quality is lower than a target value and decides the transmission power control value to the mobile station so as to cause the mobile station to decrease the transmission value when the signal quality is higher than the target value.

A radio signal quality measurement method comprising:

• calculating a radio signal power of a radio signal received from an apparatus of radio communication destination;
• determining whether or not a transmission rate change is expected to occur based on a first index representing a transmission rate of received data transmitted from the apparatus of radio communication destination and, one of a second index representing a resource assigned to the apparatus of radio communication destination and a third index representing an amount of data buffered in the apparatus of radio communication destination and to be transmitted,
• setting a measurement period which is to be used for calculating an interference power to a first length when a period in which the transmission rate change is expected not to occur exceeds a certain period, while setting the measurement period to a second length shorter than the first length when the transmission rate change is expected to occur;
• calculating an interference power by averaging power of interference wave over the measurement period;
• and
• calculating signal quality of the radio signal received from the mobile station based on the radio signal power and the interference power.