A mobile terminal apparatus comprising: a channel estimation section configured to perform channel estimation using a downlink reference signal; characterized by: a PMI selecting section configured to select a PMI, Precoding Matrix Indicator, using a channel estimation value obtained in the channel estimation section; an IQI measuring section configured to obtain an IQI, Interference Quality Indicator, using at least the channel estimation value and the PMI; and a transmission section configured to transmit at least the PMI and the IQI to a radio base station apparatus, wherein the IQI measuring section is configured to obtain the IQI using following equation, or: IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2, ∀ i, j = 1, 2, 3 IQI i j = P avg, i ICI i + N i i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i IQI i i = P avg, i ICI i + N i + P avg, i × ‖ H i i - λ i, max i ⁢ F i i H ‖ 2 i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i λ i, max i = max eigenvalue H i i H i j: Downlink channel state; F i j: PMI feedback from a mobile terminal apparatus i; P avg,j: Average total transmission power of a radio base station apparatus j; ICI i: Interference except interference from a cell belonging to a CoMP set in the mobile terminal apparatus i; and N i: Average noise in a receiver in the mobile terminal apparatus i. a channel estimation section configured to perform channel estimation using a downlink reference signal; characterized by: a PMI selecting section configured to select a PMI, Precoding Matrix Indicator, using a channel estimation value obtained in the channel estimation section; an IQI measuring section configured to obtain an IQI, Interference Quality Indicator, using at least the channel estimation value and the PMI; and a transmission section configured to transmit at least the PMI and the IQI to a radio base station apparatus, wherein the IQI measuring section is configured to obtain the IQI using following equation, or: IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2, ∀ i, j = 1, 2, 3 IQI i j = P avg, i ICI i + N i i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i IQI i i = P avg, i ICI i + N i + P avg, i × ‖ H i i - λ i, max i ⁢ F i i H ‖ 2 i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i λ i, max i = max eigenvalue H i i H i j: Downlink channel state; F i j: PMI feedback from a mobile terminal apparatus i; P avg,j: Average total transmission power of a radio base station apparatus j; ICI i: Interference except interference from a cell belonging to a CoMP set in the mobile terminal apparatus i; and N i: Average noise in a receiver in the mobile terminal apparatus i. a PMI selecting section configured to select a PMI, Precoding Matrix Indicator, using a channel estimation value obtained in the channel estimation section; an IQI measuring section configured to obtain an IQI, Interference Quality Indicator, using at least the channel estimation value and the PMI; and a transmission section configured to transmit at least the PMI and the IQI to a radio base station apparatus, wherein the IQI measuring section is configured to obtain the IQI using following equation, or: IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2, ∀ i, j = 1, 2, 3 IQI i j = P avg, i ICI i + N i i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i IQI i i = P avg, i ICI i + N i + P avg, i × ‖ H i i - λ i, max i ⁢ F i i H ‖ 2 i = j IQI i j = P avg, j ICI i + N i + P avg, j × ‖ H i j - F i j H ‖ 2 j ≠ i λ i, max i = max eigenvalue H i i H i j: Downlink channel state; F i j: PMI feedback from a mobile terminal apparatus i; P avg,j: Average total transmission power of a radio base station apparatus j; ICI i: Interference except interference from a cell belonging to a CoMP set in the mobile terminal apparatus i; and N i: Average noise in a receiver in the mobile terminal apparatus i. H i j: Downlink channel state; F i j: PMI feedback from a mobile terminal apparatus i; P avg,j: Average total transmission power of a radio base station apparatus j; ICI i: Interference except interference from a cell belonging to a CoMP set in the mobile terminal apparatus i; and N i: Average noise in a receiver in the mobile terminal apparatus i.