Communication control method, user terminal, and base station

A user terminal, comprising:

• a receiver configured to receive a downlink reference signal transmitted from a base station, the base station transmitting the downlink reference signal through a plurality of antenna ports;
• a transmitter configured to transmit precoder matrix information, antenna port information, and channel quality information to the base station, wherein
• the precoder matrix information indicates a precoder matrix preferred to be used in a downlink,
• the antenna port information indicates an antenna port with low degree of contribution, the antenna port with low degree of contribution being an antenna port amongst the plurality of antenna ports, wherein a received power of the downlink reference signal associated with the antenna port with low degree of contribution, measured by the user terminal, is low in comparison with received powers associated with other antenna ports of the plurality of antenna ports, and
• the channel quality information indicates a modulation scheme and coding rate preferred to be used in the downlink, the channel quality information being corrected in correspondence with an anticipated quality deterioration related to the antenna port with low degree of contribution.

A base station, comprising:

• a transmitter configured to transmit a downlink reference signal to a user terminal through a plurality of antenna ports,
• a receiver configured to receive precoder matrix information, antenna port information, and channel quality information from the user terminal, wherein
• the precoder matrix information indicates a precoder matrix preferred to be used in a downlink,
• the antenna port information indicates an antenna port with low degree of contribution, the antenna port with low degree of contribution being an antenna port amongst the plurality of antenna ports, wherein a received power of the downlink reference signal associated with the antenna port with low degree of contribution, measured by the user terminal, is low in comparison with received powers associated with other antenna ports of the plurality of antenna ports, and
• the channel quality information indicates a modulation scheme and coding rate preferred to be used in the downlink, the channel quality information being corrected in correspondence with an anticipated quality deterioration related to the antenna port with low degree of contribution.

A mobile communication system comprising:

• a base station that performs downlink transmission by applying a precoder matrix for determining downlink transmission directionality;
• and
• a user terminal that feeds back plural pieces of precoder matrix information corresponding to one frequency band to the base station, wherein
• the user terminal further feeds back channel quality information to the base station, the channel quality information indicating a modulation scheme and coding rate preferred to be used in a downlink, and
• the channel quality information is determined based on a precoder matrix information which is not preferred among the plural pieces of precoder matrix information.

A user terminal in a mobile communication system, comprising:

• a receiver configured to receive a radio signal from a base station;
• and
• a transmitter configured to feed back plural pieces of precoder matrix information corresponding to one frequency band to the base station, the base station performing downlink transmission by applying a precoder matrix for determining downlink transmission directionality, wherein
• the transmitter is further configured to feed back channel quality information to the base station, the channel quality information indicating a modulation scheme and coding rate preferred to be used in a downlink, and
• the channel quality information is determined based on a precoder matrix information which is not preferred among the plural pieces of precoder matrix information.

A base station, in a mobile communication system, comprising:

• a controller configured to perform downlink transmission by applying a precoder matrix for determining downlink transmission directionality;
• a transmitter configured to transmit a radio signal to a user terminal;
• and
• a receiver configured to receive, plural pieces of precoder matrix information corresponding to one frequency band, which is fed back from the user terminal, wherein
• the receiver is further configured to receive channel quality information fed back from the user terminal, the channel quality information indicating a modulation scheme and coding rate preferred, by the user terminal, to be used in a downlink, and
• the channel quality information is determined based on a precoder matrix information which is not preferred by the user terminal, among the plural pieces of precoder matrix information.