Patent ID: 8873663

Claim:
A mobile station apparatus in a Multi Input Multi Output (MIMO) system in which a base station apparatus switches between Single User MIMO (SU-MIMO) transmission and Zero Forcing MIMO (ZF MU-MIMO) transmission based on feedback information from the mobile station apparatus to perform data transmission, comprising: a selecting section configured to select Rank Indicator (RI) and to select a Precoding Matrix Indicator (PMI) identifying a precoding matrix minimizing a chordal distance between the precoding matrix and an orthonormalized unitary matrix obtained from an Hermitian transpose of a channel matrix indicative of channel characteristics; a calculating section configured to calculate a Channel Quality Indicator (CQI) from the PMI; and a feedback section configured to transmit the PMI, the RI and the CQI to the base station apparatus as the feedback information.