Wireless communication apparatus, wireless communication system and wireless communication method
In a MIMO system using a cross-polarized antenna structure, even if no ideal XPD can be obtained, the interference between different polarized waves can be reduced to allow an effective precoding to be executed. When a MIMO communication is performed between a transmitter and a receiver each using a cross-polarized antenna structure, a channel estimating and precoding selection section of the receiver performs a channel estimation of MIMO channels from the transmitter to the receiver, decides a precoding matrix of a projection matrix for mutually orthogonalizing or substantially orthogonalizing the channel response matrixes for respective different polarized waves, and feeds the determined precoding matrix back to the transmitter. In the transmitter, a precoding processing section applies the precoding matrix to the spatial stream corresponding to one of the polarized waves to perform a precoding, thereby allowing the transmitter to transmit the polarized waves with the orthogonality therebetween maintained.
1. A terminal apparatus comprising:
a selecting section configured to select a first precoding matrix and a second precoding matrix, the first precoding matrix being to be applied to a signal which is to be transmitted from both of a first set of antennas and a second set of antennas that a communication partner apparatus has, the second precoding matrix being to be applied only to a signal which is to be transmitted from the second set of antennas, wherein the first set of antennas are cross-polarized with respect to the second set of antennas, and selection of the second precoding matrix is performed in order to maintain an orthogonality between polarized waves from the first set of antennas and further polarized waves from the second set of antennas; and
a notification section configured to notify the communication partner apparatus of control information including precoding matrix information (PMI) indicating the first precoding matrix and the second precoding matrix.
2. The terminal apparatus according to claim 1 , wherein
the selection of the first precoding matrix and the second precoding matrix is performed using a codebook including a plurality of precoding matrices; and
a value of the PMI corresponds to an index indicating a precoding matrix included in the codebook.
3. The terminal apparatus according to claim 1 , wherein
the polarized waves from the first set of antennas are vertically polarized and the further polarized waves from the second set of antennas are horizontally polarized.
4. The terminal apparatus according to claim 1 , wherein
a number of antennas included in the first set of antennas and a number of antennas included in the second set of antennas are four; and
each of the first precoding matrix and the second precoding matrix is a matrix with four rows.
5. A communication method comprising:
selecting a first precoding matrix and a second precoding matrix, the first precoding matrix being to be applied to a signal which is to be transmitted from both of a first set of antennas and a second set of antennas that a communication partner apparatus has, the second precoding matrix being to be applied only to a signal which is to be transmitted from the second set of antennas, wherein the first set of antennas are cross-polarized with respect to the second set of antennas, and selection of the second precoding matrix is performed in order to maintain an orthogonality between polarized waves from the first set of antennas and further polarized waves from the second set of antennas; and
notifying the communication partner apparatus of control information including precoding matrix information (PMI) indicating the first precoding matrix and the second precoding matrix.
6. The communication method according to claim 5 , wherein
the selection of the first precoding matrix and the second precoding matrix is performed using a codebook including a plurality of precoding matrices; and
a value of the PMI corresponds to an index indicating a precoding matrix included in the codebook.
7. The communication method according to claim 5 , wherein
the polarized waves from the first set of antennas are vertically polarized and the further polarized waves from the second set of antennas are horizontally polarized.
8. The communication method according to claim 5 , wherein
a number of antennas included in the first set of antennas and a number of antennas included in the second set of antennas are four; and
each of the first precoding matrix and the second precoding matrix is a matrix with four rows.
9. An integrated circuit for controlling a process comprising:
selecting a first precoding matrix and a second precoding matrix, the first precoding matrix being to be applied to a signal which is to be transmitted from both of a first set of antennas and a second set of antennas that a communication partner apparatus has, the second precoding matrix being to be applied only to a signal which is to be transmitted from the second set of antennas, wherein the first set of antennas are cross-polarized with respect to the second set of antennas, and selection of the second precoding matrix is performed in order to maintain an orthogonality between polarized waves from the first set of antennas and further polarized waves from the second set of antennas; and
notifying the communication partner apparatus of control information including precoding matrix information (PMI) indicating the first precoding matrix and the second precoding matrix.
10. The integrated circuit according to claim 9 , wherein the polarized waves from the first set of antennas are vertically polarized and the further polarized waves from the second set of antennas are horizontally polarized.