APPARATUS AND METHOD FOR TRANSMITTING DATA BASED ON QUANTIZED CHANNEL STATE INFORMATION

• US 20100048232A1
• Filed: 05/22/2009
• Published: 02/25/2010
• Est. Priority Date: 08/20/2008
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Ki Il, Hwang, Duck Dong
• Granted Patent: US 8,385,957 B2
• Time in Patent Office: Days
• US Class Current: 455/501
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 2025/03802 Signalling on the reverse channel
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

A base station apparatus including a receiving unit to receive, from a terminal, quantized channel state information with respect to a radio channel from a plurality of transmission antennas of the base station apparatus to a plurality of receiving antennas of the terminal. A control unit to determine a control ratio of interference signal to noise with respect to the radio channel based on the channel state information. A precoding matrix computing unit to compute a precoding matrix based on the control ratio of interference signal to noise and a transmission unit to transmit data to one or more of the connected terminals using the precoding matrix.

Claims

1. A base station apparatus, comprising:

a receiving unit to receive, from a terminal, quantized channel state information with respect to a radio channel from a plurality of transmission antennas of the base station apparatus to a plurality of receiving antennas of the terminal;

a control unit to determine a control ratio of interference signal to noise with respect to the radio channel based on the channel state information;

a precoding matrix computing unit to compute a precoding matrix based on the control ratio of interference signal to noise; and

a transmission unit to transmit data to one or more terminals using the precoding matrix.

2. The base station apparatus of claim 1, wherein the control unit determines the control ratio of interference signal to noise based on a number of quantization bits of the channel state information.

3. The base station apparatus of claim 1, further comprising:

a channel matrix generating unit to generate a radio channel state matrix with respect to the radio channel based on the received quantized channel state information; and

a singular value decomposing unit to perform a singular value decomposition with respect to the radio channel state matrix,

wherein the control unit determines the control ratio of interference signal to noise based on the singular value of the radio channel state matrix.

4. The base station apparatus of claim 3, wherein the control ratio of interference signal to noise satisfies the following equation:

$\underset{l=1}{\overset{{\mathrm{KN}}_r}{\sum <br><br>}}<br><br><br><br>\underset{k=1}{\overset{l-1}{\sum <br><br>}}<br><br><br><br>\frac{{\mathrm{\lambda <br><br>}}_k^2<br><br>{{\mathrm{\lambda <br><br>}}_l^2<br><br>\left({\mathrm{\lambda <br><br>}}_k^2-{\mathrm{\lambda <br><br>}}_l^2\right)}^2<br><br>\left({\mathrm{KN}}_r/P-\mathrm{\alpha <br><br>}\right)}{{\left({\mathrm{\lambda <br><br>}}_l^2+\mathrm{\alpha <br><br>}\right)}^3<br><br>{\left({\mathrm{\lambda <br><br>}}_k^2+\mathrm{\alpha <br><br>}\right)}^3}=4<br><br>{\mathrm{KN}}_r<br><br>q<br><br>\sum <br><br>\frac{{\mathrm{\lambda <br><br>}}_k^2}{{\left({\mathrm{\lambda <br><br>}}_k^2+\mathrm{\alpha <br><br>}\right)}^2},$

wherein K denotes a number of all terminals connected to the base station apparatus, N_r denotes a number of receiving antennas of each of the connected terminals, λ

_k and λ

_l respectively denote a k-th singular value and l-th singular value of the radio channel state matrix, α

denotes the control ratio of interference signal to noise, P denotes the precoding matrix, and where q is represented as;

$q=\frac{1}{2}·<br><br>\underset{i=0}{\overset{N}{\sum <br><br>}}<br><br><br><br>\left(\begin{array}{c}N\\ i\end{array}\right)·<br><br>I_i·<br><br>\left[{\left(\frac{1}{2}\right)}^N+{\left(-\frac{1}{2}\right)}^i\right],$

wherein N=2^B, where B denotes a number of quantization bits with respect to the channel state information, and I_i (i=0, 1, 2, . . . , N) is represented as;

I_i=∫

₀¹[4x(1−

x)]<sup>i(M−

1)</sup>dx,

wherein M denotes a number of transmission antennas.

5. The base station apparatus of claim 1, wherein the control unit determines the control ratio of interference signal to noise based on a number of transmission antennas of the base station apparatus and a number of the receiving antennas of the terminal.

6. The base station apparatus of claim 5, wherein the control unit determines the control ratio of interference signal to noise according to the following equations:

wherein α

denotes the control ratio of interference signal to noise, K denotes a number of all terminals connected with the base station apparatus, N_r denotes a number of receiving antennas of each of the connected terminals, P denotes the precoding matrix, M denotes a number of transmission antennas of the base station apparatus, and where q is determined by the following equation;

$q=\frac{1}{2}·<br><br>\underset{i=0}{\overset{N}{\sum <br><br>}}<br><br><br><br>\left(\begin{array}{c}N\\ i\end{array}\right)·<br><br>I_i·<br><br>\left[{\left(\frac{1}{2}\right)}^N+{\left(-\frac{1}{2}\right)}^i\right],$

wherein N=2^B where B denotes a number of quantization bits with respect to the channel state information, and where I_i (i=0, 1, 2, . . . N) is represented as;

I_i∫

₀¹[4x(1−

x)]<sup>i(M−

1)</sup>dx.

7. The base station apparatus of claim 1, further comprising:

a channel matrix generating unit to generate a radio channel state matrix from the plurality of transmission antennas of the base station apparatus to the plurality of receiving antennas of the terminal based on the received quantized channel state information; and

a singular value decomposing unit to perform a singular value decomposition with respect to the radio channel state matrix,

wherein the precoding matrix computing unit computes the precoding matrix based on results of the singular value decomposition with respect to the radio channel state matrix.

8. The base station apparatus of claim 7, wherein the precoding matrix is represented as:

$P=V·<br><br>\mathrm{\Lambda <br><br>}\left(\frac{\mathrm{\lambda <br><br>}}{{\mathrm{\lambda <br><br>}}^2+\mathrm{\alpha <br><br>}}\right)·<br><br>U^{+}·<br><br>D,$

wherein P denotes the precoding matrix, V denotes a right singular matrix with respect to a radio channel state matrix, U denotes a left singular matrix with respect to the radio channel state matrix, + denotes a Hermitian transpose, and Λ

(x) and D are, respectively, as the following equations;

$\mathrm{\Lambda <br><br>}<br><br>\left(x\right)=\left[\begin{array}{ccc}{x}_1& 0& 0\\ 0& \mathrm{\ddots <br><br>}& 0\\ 0& 0& x_N\\ 0& 0& 0\\ 0& 0& 0\end{array}\right],$

wherein x_n denotes an n-th singular value with respect to the radio channel state matrix, and

$D=\left[\begin{array}{ccc}{D}_{11}& 0& 0\\ 0& \mathrm{\ddots <br><br>}& 0\\ 0& 0& D_{\mathrm{KK}}\end{array}\right],$

wherein D_kk=H_k⁺·

T_k, H_k denotes a radio channel state matrix associated with a k-th terminal, and T_k is represented as;

T_k=basis[II₁ . . . II<sub>k−

1</sub>II_k+1 . . . II_K]^⊥

9. A data transmission method for a base station in a wireless communication system, the method comprising:

receiving, from a terminal at the base station, quantized channel state information with respect to a radio channel from a plurality of transmission antennas of the base station to a plurality of receiving antennas of a terminal;

determining, by a control unit of the base station, a control ratio of interference signal to noise with respect to the radio channel based on the channel state information;

computing, by a precoding matrix computing unit of the base station, a precoding matrix based on the control ratio of interference signal to noise; and

transmitting data from the plurality of antennas of the base station to one or more terminals using the precoding matrix.

10. The method of claim 9, wherein determining the control ratio of interference signal to noise is based on a number of quantization bits of the channel state information.

11. The method of claim 9, further comprising:

generating, by a channel radio matrix generation unit of the base station, a radio channel state matrix with respect to the radio channel based on the received quantized channel state information; and

performing, by a singular value decomposing unit of the base station, a singular value decomposition with respect to the radio channel state matrix, wherein determining the control ratio of interference signal to noise is based on the singular value of the radio channel state matrix.

12. The method of claim 11, wherein the control ratio of reference signal to noise satisfies the following equation:

$\underset{l=1}{\overset{{\mathrm{KN}}_r}{\sum <br><br>}}<br><br><br><br>\underset{k=1}{\overset{l-1}{\sum <br><br>}}<br><br><br><br>\frac{{\mathrm{\lambda <br><br>}}_k^2<br><br>{{\mathrm{\lambda <br><br>}}_l^2<br><br>\left({\mathrm{\lambda <br><br>}}_k^2-{\mathrm{\lambda <br><br>}}_l^2\right)}^2<br><br>\left({\mathrm{KN}}_r/P-\mathrm{\alpha <br><br>}\right)}{{\left({\mathrm{\lambda <br><br>}}_l^2+\mathrm{\alpha <br><br>}\right)}^3<br><br>{\left({\mathrm{\lambda <br><br>}}_k^2+\mathrm{\alpha <br><br>}\right)}^3}=4<br><br>{\mathrm{KN}}_r<br><br>q<br><br>\sum <br><br>\frac{{\mathrm{\lambda <br><br>}}_k^2}{{\left({\mathrm{\lambda <br><br>}}_k^2+\mathrm{\alpha <br><br>}\right)}^2},$

wherein K denotes a number of all terminals connected to the base station apparatus, N_r denotes a number of receiving antennas of each of the connected terminals, P denotes the precoding matrix, λ

_k and λ

_l respectively denote a k-th singular value and 1-st singular value of the radio channel state matrix, α

denotes the control ratio of interference singular to noise, and q is represented as;

$q=\frac{1}{2}·<br><br>\underset{i=0}{\overset{N}{\sum <br><br>}}<br><br><br><br>\left(\begin{array}{c}N\\ i\end{array}\right)·<br><br>I_i·<br><br>\left[{\left(\frac{1}{2}\right)}^N+{\left(-\frac{1}{2}\right)}^i\right],$

wherein N=2^B, where B denotes a number of quantization bits with respect to the channel state information, and I_i (i=0, 1, 2, . . . N) is represented as;

I_i=∫

₀¹[4x(1−

x)]<sup>i(M−

1)</sup>dx,

wherein M denotes the number of transmission antennas of the base station.

13. The method of claim 9, wherein determining the control ratio of interference signal to noise is based on a number of the transmission antennas of the base station and a number of receiving antennas of the terminal.

14. The method of claim 13, wherein determining the control ratio of interference signal to noise is calculated in accordance with:

$\mathrm{\alpha <br><br>}=\frac{{\mathrm{KN}}_r}{P}+\frac{4<br><br>\left({\mathrm{KN}}_r-1\right)<br><br>\mathrm{Mq}}{{\left({\mathrm{KN}}_r\right)}^2},$

wherein α

denotes the control ratio of interference signal to noise, K denotes a number of all terminals connected with the base station apparatus, N_r denotes a number of receiving antennas of each of the connected terminals, P denotes the precoding matrix, M denotes a number of transmission antennas of the base station apparatus, and q is represented as;

$q=\frac{1}{2}·<br><br>\underset{i=0}{\overset{N}{\sum <br><br>}}<br><br><br><br>\left(\begin{array}{c}N\\ i\end{array}\right)·<br><br>I_i·<br><br>\left[{\left(\frac{1}{2}\right)}^N+{\left(-\frac{1}{2}\right)}^i\right],$

wherein N=2^B, where B denotes a number of quantization bits with respect to the channel state information, and I_i (i=0, 1, 2, . . . N) is represented as;

I_i=∫

₀¹[4x(1−

x)]<sup>i(M−

1)</sup>dx,

15. The method of claim 9, further comprising:

generating, by a channel matrix generating unit of the base station, a radio channel state matrix from the plurality of transmission antennas of the base station to the plurality of receiving antennas of the terminal based on the received quantized channel state information; and

performing, by a singular value decomposing unit of the base station, a singular value decomposition with respect to the radio channel state matrix, wherein computing the precoding matrix is based on results of the singular value decomposition with respect to the radio channel state matrix.

16. The method of claim 15, wherein the precoding matrix is represented as:

$P=V·<br><br>\mathrm{\Lambda <br><br>}\left(\frac{\mathrm{\lambda <br><br>}}{{\mathrm{\lambda <br><br>}}^2+\mathrm{\alpha <br><br>}}\right)·<br><br>U^{+}·<br><br>D,$

wherein P denotes the precoding matrix, V denotes a right singular matrix with respect to a radio channel state matrix, U denotes a left singular matrix with respect to the radio channel state matrix, + denotes a Hermitian transpose, and Λ

(x) and D are respectively represented as;

$\mathrm{\Lambda <br><br>}<br><br>\left(x\right)=\left[\begin{array}{ccc}{x}_1& 0& 0\\ 0& \mathrm{\ddots <br><br>}& 0\\ 0& 0& x_N\\ 0& 0& 0\\ 0& 0& 0\end{array}\right],$

wherein x_n denotes an n-th singular value with respect to the radio channel state matrix, and

$D=\left[\begin{array}{ccc}{D}_{11}& 0& 0\\ 0& \mathrm{\ddots <br><br>}& 0\\ 0& 0& D_{\mathrm{KK}}\end{array}\right],$

wherein D_kk=H_k⁺·

T_k, H_k denotes a radio channel state matrix associated with a k-th terminal, and T_k is represented as;

T_k=basis[H₁ . . . H<sub>k−

1</sub>H_k+1 . . . H_K]^⊥

17. A computer-readable recording medium storing a program comprising instructions to cause a computer to:

receive quantized channel state information with respect to a radio channel from a plurality of transmission antennas of a base station to a plurality of receiving antennas of a terminal;

determine a control ratio of interference signal to noise with respect to the radio channel based on the channel state information;

compute a precoding matrix based on the control ratio of interference signal to noise; and

transmit transmitting data to the terminal using the precoding matrix.

18. A terminal comprising:

a transmission unit to transmit, to a base station, quantized state information with respect to a radio channel from a plurality of transmission antennas of the base station to a plurality of reception antennas of the terminal; and

a reception unit to receive data transmitted from the base station that was precoded using a precoding matrix generated based on the state information,

wherein the state information was used to determine a control ratio of interference signal to noise with respect to the radio channel, and the precoding matrix is generated based on the control ratio of interference signal to noise.

19. The terminal of claim 18, wherein the control ratio of interference signal to noise is determined based on a number of quantization bits of the channel state information.