Base station apparatus, terminal apparatus, and communication method
To provide a base station apparatus, a terminal apparatus, and a communication method capable of improving a frequency efficiency or throughput by suppressing an overhead associated with feedback from the terminal apparatus in a case that the base station apparatus acquires highly accurate CSI. A terminal apparatus according to an aspect of the present invention includes a receiver configured to receive at least one NZP CSI-RS, and a transmitter configured to transmit a signal including at least one piece of CSI. The at least one piece of CSI includes at least an RI and a PMI, the receiver acquires a first value for configuring the number of vectors indicated by the PMI, and in a case that a value of the RI exceeds a prescribed value, the number of vectors is configured by a second value being a value equal to or less than the first value.
1. A base station apparatus configured to communicate with a terminal apparatus, the base station apparatus comprising:
transmission circuitry configured to transmit a non-zero power (NZP) channel state information reference signal (CSI-RS) and radio resource control (RRC) signaling; and
reception circuitry configured to receive channel state information (C SI) corresponding to the NZP CSI-RS, wherein
the CSI includes at least a rank indicator (RI) and a precoding matrix indicator (PMI) that includes a plurality of indicators, the plurality of indicators indicating a plurality of vectors,
a quantity of vectors of the plurality of vectors is determined based on a first value or a second value, the first value and the second value being indicated by the RRC signaling,
the first value indicated by the RRC signaling in a case of a value of the RI being more than 2,
the second value indicated by the RRC signaling in a case of a value of the RI being 2 or less, and
the first value is equal to or smaller than the second value.
2. A terminal apparatus configured to communicate with a base station apparatus, the terminal apparatus comprising:
reception circuitry configured to receive a non-zero power (NZP) channel state information reference signal (CSI-RS) and radio resource control (RRC) signaling; and
transmission circuitry configured to transmit channel state information (CSI) corresponding to the NZP CSI-RS, wherein
the CSI includes at least a rank indicator (RI) and a precoding matrix indicator (PMI) that includes a plurality of indicators, the plurality of indicators indicating a plurality of vectors,
a quantity of vectors of the plurality of vectors is determined based on a first value or a second value, the first value and the second value being indicated by the RRC signaling,
the first value indicated by the RRC signaling in a case of a value of the RI being more than 2,
the second value indicated by the RRC signaling in a case of a value of the RI being 2 or less, and
the first value is equal to or smaller than the second value.
3. A communication method for a base station apparatus configured to communicate with a terminal apparatus, the communication method comprising:
transmitting a non-zero power (NZP) channel state information reference signal (CSI-RS) and radio resource control (RRC) signaling; and
receiving channel state information (CSI) corresponding to the NZP CSI-RS, wherein
the CSI includes at least a rank indicator (RI) and a precoding matrix indicator (PMI) that includes a plurality of indicators, the plurality of indicators indicating a plurality of vectors,
a quantity of vectors of the plurality of vectors is determined based on a first value or a second value, the first value and the second value being indicated by the RRC signaling,
the first value indicated by the RRC signaling in a case of a value of the RI being more than 2,
the second value indicated by the RRC signaling in a case of a value of the RI being 2 or less, and
the first value is equal to or smaller than the second value.
4. A communication method for a terminal apparatus configured to communicate with a base station apparatus, the communication method comprising:
receiving a non-zero power (NZP) channel state information reference signal (CSI-RS) and radio resource control (RRC) signaling; and
transmitting channel state information (CSI) corresponding to the NZP CSI-RS, wherein
the CSI includes at least a rank indicator (RI) and a precoding matrix indicator (PMI) that includes a plurality of indicators, the plurality of indicators indicating a plurality of vectors,
a quantity of vectors of the plurality of vectors is determined based on a first value or a second value, the first value and the second value being indicated by the RRC signaling,
the first value indicated by the RRC signaling in a case of a value of the RI being more than 2,
the second value indicated by the RRC signaling in a case of a value of the RI being 2 or less, and
the first value is equal to or smaller than the second value.