In an LTE (Long Term Evolution) system of which the specifications are designed in 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, CoMP (Coordinated Multi-Point) is specified in its Release 11 (see Non Patent Literature 1).
In the current specification, CoMP is assumed in which a plurality of cells managed by the same base station cooperate with one another to perform communication with one user terminal (that is, Intra-eNB CoMP).
Furthermore, as one scheme of the CoMP, CB (Coordinated Beamforming)-CoMP is discussed. The CB-CoMP represents a scheme in which a plurality of cells cooperate with one another to perform beamforming and null steering.
In the CB-CoMP, a base station that manages a plurality of cells receives a first precoder matrix indicator fed back from a first user terminal connected with a first cell and a second precoder matrix indicator fed back from a second user terminal connected with a second cell.
For example, the first precoder matrix indicator is an indicator for directing a null to the first user terminal, and is a BCI (Best Companion-Precoding Matrix Indicator) or a WCI (Worst Companion-Precoding Matrix Indicator). Furthermore, the second precoder matrix indicator is an indicator for directing a beam to the second user terminal, and is a PMI (Precoding Matrix Indicator).
Then, the base station allocates the same time-frequency resource as the time-frequency resource allocated to the first user terminal, to the second user terminal which feeds back the second precoder matrix indicator that matches the first precoder matrix indicator. Furthermore, the base station directs a null to the first user terminal and a beam to the second user terminal by applying the matched second precoder matrix indicator.