Method and apparatus for antenna array channel feedback
A method and apparatus provide antenna array channel feedback. The method can include receiving, at a wireless terminal, a set of channel state information reference signals. The method can include determining, by the wireless terminal, based on the received set of channel state information reference signals, a precoding matrix that is a product of a first precoding matrix and a second precoding matrix. The first precoding matrix can have at least a representation in terms of a representation matrix. The representation matrix can be based on a matrix selected from a first codebook. The second precoding matrix can be based on a second codebook. The method can include transmitting, by the wireless terminal, a representation of at least one of the first precoding matrix and the second precoding matrix.
1. A method comprising:
receiving, at a wireless terminal, a set of channel state information reference signals;
determining, by the wireless terminal, based on the received set of channel state information reference signals, a precoding matrix that is a product of a first precoding matrix and a second precoding matrix, where the first precoding matrix has at least a representation in terms of a representation matrix, where the representation matrix is based on a matrix selected from a first codebook, and where the second precoding matrix is based on a second codebook; and
transmitting, by the wireless terminal, a representation of at least one of the first precoding matrix and the second precoding matrix;
wherein the product is a block-Kronecker product;
wherein the block-Kronecker product of two matrices is a horizontal concatenation of a sequence of one or more matrix block products where each of the two matrices is composed of a sequence of one or more horizontally concatenated matrix blocks;
wherein an i th matrix block product of the sequence of horizontally concatenated matrix blocks is equal to a Kronecker matrix product of the i th matrix block of a first matrix of the two matrices and the i th matrix block of a second matrix of the two matrices;
wherein the block-Kronecker product comprises:
P V *P H =[P V (:,1) P H (:,1) P V (:,2) P H (:,2) . . . P V (:, r ) P H (:, r )],
where P V is the first precoding matrix, and
where P H is the second precoding matrix, and
r is the number of spatial layers.
2. The method of claim 1 , wherein the first precoding matrix has at least a representation in terms of a plurality of representation matrices.
3. The method of claim 1 wherein:
P
V
(
:
,
p
)
=
[
1
ⅇ
jϕ
p
⋮
ⅇ
j
(
M
-
1
)
ϕ
p
]
,
where p is a codebook precoding matrix.
4. The method of claim 1 , wherein transmitting further comprises transmitting, by the wireless terminal, a first channel state information report including at least the representation of the first precoding matrix in a first uplink subframe and a second channel state information report including at least the second precoding matrix in a second uplink subframe.
5. The method of claim 4 , wherein the first uplink subframe occurs at a different time from the second uplink subframe.
6. The method of claim 5 , wherein the first and second channel state information reports are transmitted with different periodicities.
7. The method of claim 4 , wherein the first channel state information report and the second channel state information report are transmitted periodically.
8. The method of claim 1 , wherein transmitting comprises transmitting, by the wireless terminal, a representation of at least one of the first precoding matrix and the second precoding matrix over one of a Physical Uplink Shared Channel and a Physical Uplink Control Channel.
9. An apparatus comprising:
a receiver configured to receive a set of channel state information reference signals;
a controller coupled to the receiver, the controller configured to determine, based on the received set of channel state information reference signals, a precoding matrix that is a product of a first precoding matrix and a second precoding matrix, where the first precoding matrix has at least a representation in terms a representation matrix, where the representation matrix is based on a matrix selected from a first codebook, and where the second precoding matrix is based on a second codebook; and
a transmitter coupled to the controller, the transmitter configured to transmit a representation of at least one of the first precoding matrix and the second precoding matrix;
wherein the product is a block-Kronecker product;
wherein the block-Kronecker product of two matrices is a horizontal concatenation of a sequence of one or more matrix block products where each of the two matrices is composed of a sequence of one or more horizontally concatenated matrix blocks;
wherein an i th matrix block product of the sequence of horizontally concatenated matrix blocks is equal to a Kronecker matrix product of the i th matrix block of a first matrix of the two matrices and the i th matrix block of a second matrix of the two matrices;
wherein the block-Kronecker product comprises:
P V *P H =[P V (:,1) P H (:,1) P V (:,2) P H (:,2) . . . P V (:, r ) P H (:, r )],
where P V is the first precoding matrix, and
where P H is the second precoding matrix, and
r is the number of spatial layers.
10. The apparatus of claim 9 , wherein the transmitter is configured to transmit a first channel state information report including at least the representation of the first precoding matrix in a first uplink subframe and a second channel state information report including at least the second precoding matrix in a second uplink subframe.