Apparatus and method for channel state information codeword construction for a cellular wireless communication system
A mobile station configured to receive transmissions from a two-dimensional array of antennas at a base station is provided. A main processor of the mobile station is configured to estimate first and second channel states and determine a co-phasing scalar component for each of multiple groups of antennas in the array based on the first channel state. The main processor is configured to generate a matrix X that includes a plurality of column vectors selected from a codebook based on the second channel state, generate a matrix P 1 , wherein the matrix P 1 is a block diagonal matrix having the matrix X for each block diagonal element, and generate a matrix P 2 . The main processor is also configured to transmit to the base station information corresponding to the matrix P 1 and to the matrix P 2 , as well as a CQI that is derived with a precoding matrix P defined by P=P 1 P 2 .
1. A mobile station configured to receive transmissions from a two-dimensional array of antennas at a base station, wherein the array comprises a plurality of groups of antennas, the mobile station comprising a main processor, the main processor configured:
to receive from the base station a first configuration for a first set of reference signals and a second configuration for a second set of reference signals;
to estimate a first channel state with the first set of reference signals and a second channel state with the second set of reference signals;
to determine a co-phasing scalar component for each of the groups of antennas based on the first channel state;
to generate a matrix X comprising a plurality of column vectors selected from a codebook based on the second channel state, wherein each of the column vectors quantizes channel coefficients for one of the groups of antennas;
to generate a matrix P 1 , wherein the matrix P 1 comprises a block diagonal matrix having the matrix X for each block diagonal element;
to generate a matrix P 2 comprising a plurality of vector elements, wherein each vector element comprises one of the co-phasing scalar components and a column selector vector configured to select a column of the matrix X;
to transmit to the base station a first precoding matrix information corresponding to the matrix P 1 and a second precoding matrix information corresponding to the matrix P 2 ; and
to transmit to the base station a channel quality information (CQI), wherein the CQI is derived with a precoding matrix P defined by P=P 1 P 2 .
2. The mobile station of claim 1 , wherein each group of antennas comprises antennas placed substantially on a horizontal line of the two-dimensional array of antennas.
3. The mobile station of claim 1 , wherein each group of antennas comprises antennas placed substantially on a vertical line of the two-dimensional array of antennas.
4. The mobile station of claim 1 , wherein the first set of reference signals is received from antennas in one of the groups of antennas, and wherein the second set of reference signals is received from a set of antennas comprising one antenna selected from each group of antennas.
5. The mobile station of claim 1 , wherein each column vector of X is selected from a Discrete Fourier Transform (DFT) codebook comprising DFT vectors of length being equal to a number of antennas in each of the groups of antennas, denoted by N P1 .
6. The mobile station of claim 5 , wherein the DFT codebook comprises a plurality of codewords, wherein each codeword is defined by a corresponding column of B, and wherein B is defined as:
B
=
[
b
0
b
1
…
b
N
DFT
-
1
]
,
[
B
]
1
+
m
,
1
+
n
=
ⅇ
j
2
π
mn
N
DFT
,
m
=
0
,
1
,
2
…
,
N
P
1
,
n
=
0
,
1
,
…
,
N
DFT
-
1
,
wherein N DFT is an integer multiple of N P1 .
7. A method for constructing a channel state information (CSI) codeword at a mobile station in a wireless communication system comprising a base station having a two-dimensional array of antennas, wherein the array comprises a plurality of groups of antennas, the method comprising:
receiving from the base station a first configuration for a first set of reference signals and a second configuration for a second set of reference signals;
estimating a first channel state with the first set of reference signals and a second channel state with the second set of reference signals;
determining a co-phasing scalar component for each of the groups of antennas based on the first channel state;
generating a matrix X comprising a plurality of column vectors selected from a codebook based on the second channel state, wherein each of the column vectors quantizes channel coefficients for one of the groups of antennas;
generating a matrix P 1 , wherein the matrix P 1 comprises a block diagonal matrix having the matrix X for each block diagonal element;
generating a matrix P 2 comprising a plurality of vector elements, wherein each vector element comprises one of the co-phasing scalar components and a column selector vector configured to select a column of the matrix X;
transmitting to the base station a first precoding matrix information corresponding to the matrix P 1 and a second precoding matrix information corresponding to the matrix P 2 ; and
transmitting to the base station a channel quality information (CQI), wherein the CQI is derived with a precoding matrix P defined by P=P 1 P 2 .
8. The method of claim 7 , wherein each group of antennas comprises antennas placed substantially on a horizontal line of the two-dimensional array of antennas.
9. The method of claim 7 , wherein each group of antennas comprises antennas placed substantially on a vertical line of the two-dimensional array of antennas.
10. The method of claim 7 , wherein the first set of reference signals is received from antennas in one of the groups of antennas, and wherein the second set of reference signals is received from a set of antennas comprising one antenna selected from each group of antennas.
11. The method of claim 7 , wherein each column vector of X is selected from a Discrete Fourier Transform (DFT) codebook comprising DFT vectors of length being equal to a number of antennas in each of the groups of antennas, denoted by N P1 .
12. The method of claim 11 , wherein the DFT codebook comprises a plurality of codewords, wherein each codeword is defined by a corresponding column of B, and wherein B is defined as:
B
=
[
b
0
b
1
…
b
N
DFT
-
1
]
,
[
B
]
1
+
m
,
1
+
n
=
ⅇ
j
2
π
mn
N
DFT
,
m
=
0
,
1
,
2
…
,
N
P
1
,
n
=
0
,
1
,
…
,
N
DFT
-
1
,
wherein N DFT is an integer multiple of N P1 .
13. A base station in a wireless communication system, comprising:
a two-dimensional array of antennas, wherein the array comprises a plurality of groups of antennas; and
a base transceiver subsystem (BTS) controller configured:
to transmit to a mobile station a first configuration for a first set of reference signals and a second configuration for a second set of reference signals;
to receive from the mobile station a first precoding matrix information corresponding to a matrix P 1 and a second precoding matrix information corresponding to a matrix P 2 ,
wherein a first channel state is estimated with the first set of reference signals and a second channel state is estimated with the second set of reference signals,
wherein a co-phasing scalar component is determined for each of the groups of antennas based on the first channel state,
wherein the matrix P 1 comprises a block diagonal matrix having a matrix X for each block diagonal element,
wherein the matrix P 2 comprises a plurality of vector elements, wherein each vector element comprises one of the co-phasing scalar components and a column selector vector configured to select a column of the matrix X, and
wherein the matrix X comprises a plurality of column vectors selected from a codebook based on the second channel state, wherein each of the column vectors quantizes channel coefficients for one of the groups of antennas; and
to receive from the mobile station a channel quality information (CQI), wherein the CQI is derived with a precoding matrix P defined by P=P 1 P 2 .
14. The base station of claim 13 , wherein each group of antennas comprises antennas placed substantially on a horizontal line of the two-dimensional array of antennas.
15. The base station of claim 13 , wherein each group of antennas comprises antennas placed substantially on a vertical line of the two-dimensional array of antennas.
16. The base station of claim 13 , wherein the first set of reference signals is transmitted from antennas in one of the groups of antennas, and wherein the second set of reference signals is transmitted from a set of antennas comprising one antenna selected from each group of antennas.
17. The base station of claim 13 , wherein each column vector of X is selected from a Discrete Fourier Transform (DFT) codebook comprising DFT vectors of length being equal to a number of antennas in each of the groups of antennas, denoted by N P1 .
18. The base station of claim 17 , wherein the DFT codebook comprises a plurality of codewords, wherein each codeword is defined by a corresponding column of B, and wherein B is defined as:
B
=
[
b
0
b
1
…
b
N
DFT
-
1
]
,
[
B
]
1
+
m
,
1
+
n
=
ⅇ
j
2
π
mn
N
DFT
,
m
=
0
,
1
,
2
…
,
N
P
1
,
n
=
0
,
1
,
…
,
N
DFT
-
1
,
wherein N DFT is an integer multiple of N P1 .