Beam and power allocation method for MIMO communication system

• US 20060209980A1
• Filed: 03/06/2006
• Published: 09/21/2006
• Est. Priority Date: 03/04/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Original Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Inventors: Kim, Sung-Jin, Li, Jianjun, Kim, Ho-Jin, Lee, Kwang-Bok
• Granted Patent: US 7,587,172 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0465 taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0675 characterised by the signaling

Abstract

The present invention provides the multiuser Multiple-Input Multiple-Output (MIMO) systems with a feedback method which includes measuring, at the terminal, received Signal to Noise Ratios (SNRs) for all transmit antennas, selecting one of precoding matrixes, which has best SNRs, retrieving an index mapped to the selected preceding matrix from a predetermined mapping table, and transmitting the index with the SNRs of the selected precoding matrix. In the present invention, it is possible to reduce feedback information amount without degradation of the sum rate performance of the system since the feedback information is transmitted in a form of index implying appropriate precoding matrix and corresponding SNRs.

Claims

1. A method for transmitting data in multiuser Multiple-Input Multiple-Output (MIMO) systems in which a base station performs scheduling on the basis of feedback information received from a plurality of terminals, comprising:

determining, at the base station, at least one best terminal for each transmit antenna on the basis of the feedback information;

calculating a sum rate from the feedback information;

deciding a preceding matrix and terminals for each transmit antenna, maximizing the sum rate; and

performing transmission with the decided precoding matrix and terminals.

2. The method of claim 1, wherein the best terminal for each antenna is determined by

$k_{i,j}=\arg$

 

⁢

max k ⁢

I ^ ⁢

{ 1 , 2 , …

, K } ⁢

r k , i , j ,

where r_k,i,j is a received Signal to Noise Ratio (SNR) of kth terminal, i is an index of the precoding matrix, and j is an index of a column of the precoding matrix.

3. The method of claim 1, wherein the feedback information includes all indexes of the preceding matrixes and received SNRs corresponding to the matrixes.

4. The method of claim 1, wherein the feedback information includes a single index of a precoding matrix chosen by the terminal and SNRs corresponding to the precoding matrix.

5. The method of claim 4, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

1 , k = arg ⁢

 

⁢

max i , j ⁢

r k , i , j ,

where r_k,i,j is a received SNR of a kth terminal, i is an index of the precoding matrix, and j is an index of a column of the precoding matrix.

6. The method of claim 4, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

2 , k = arg ⁢

max i ⁢

å

j ⁢

 

⁢

c f ⁡

( r k , i , j ) ,

where C_f is feedback capacity, r_k,i,j is a received SNR of kth terminal, i is an index of the precoding matrix, and j is an index of a column of the precoding matrix.

7. The method of claim 1, wherein the feedback information includes a column vector of a precoding matrix selected by the terminal and the received SNR corresponding to the column vector.

8. The method of claim 7, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

1 , k = arg ⁢

 

⁢

max i , j ⁢

r k , i , j ,

where r_k,i,j is a received SNR of a kth terminal, i is an index of the precoding matrix, and j is an index of a column of the precoding matrix.

9. A method for feeding back information in multiuser Multiple-Input Multiple-Output (MIMO) system in which a base station determining at least one best terminal for each transmit antenna on the basis of feedback information, calculating a sum rate from the feedback information, deciding a precoding matrix and terminals for each transmit antenna, performing transmission with the decided precoding matrix and terminals, the method comprising:

measuring, at the terminal, received Signal to Noise Ratios (SNRs) for all transmit antennas;

selecting one of preceding matrixes, which has a best SNR;

retrieving an index mapped to the selected preceding matrix from a predetermined mapping table; and

transmitting the index with the SNRs of the selected preceding matrix.

10. The method of claim 9, wherein the preceding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

1 , k = arg ⁢

 

⁢

max i , j ⁢

r k , i , j ,

where r_k,i,j is a received SNR of a kth terminal, i is the index of the preceding matrix, and j is the index of a column of the precoding matrix.

11. The method of claim 9, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

2 , k = arg ⁢

max i ⁢

å

j ⁢

 

⁢

c f ⁡

( r k , i , j ) ,

where c_f is feedback capacity, r_k,i,j is a received SNR of a kth terminal, i is the index of the precoding matrix, and j is an index of a column of the preceding matrix.

12. A method for feeding back information of multiuser Multiple-Input Multiple-Output (MIMO) system in which a base station determining at least one best terminal for each transmit antenna on the basis of feedback information, calculating a sum rate from the feedback information, deciding a precoding matrix and terminals for each transmit antenna, performing transmission with the decided preceding matrix and terminals, the method comprising:

measuring, at the terminal, received Signal to Noise Ratios (SNRs) for all transmit antennas;

selecting one of precoding matrixes, which has best SNRs;

extracting one of column vectors constituting the selected preceding matrix;

retrieving an index mapped to the selected preceding matrix from a predetermined mapping table; and

transmitting the index with information on the retrieved column vector and the SNRs corresponding to the column vector to the base station.

13. The method of claim 12, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

1 , k = arg ⁢

 

⁢

max i , j ⁢

r k , i , j ,

where r_k,i,j is a received SNR of a kth terminal, i is the index of the preceding matrix, and j is an index of a column of the precoding matrix.

14. A method for feeding back information of multiuser Multiple-Input Multiple-Output (MIMO) system in which a base station determining at least one best terminal for each transmit antenna on the basis of feedback information, calculating a sum rate from the feedback information, deciding a precoding matrix and terminals for each transmit antenna, performing transmission with the decided precoding matrix and terminals, the method comprising:

measuring, at the terminal, received Signal to Noise Ratios (SNRs) for all transmit antennas;

selecting one of precoding matrixes having a best SNR;

extracting one of column vectors constituting the selected preceding matrix;

retrieving an index mapped to the selected precoding matrix, column vector, and SNR corresponding to the column vector of the selected precoding matrix from a predetermined mapping table; and

transmitting the index as the feedback information to the base station.

15. The method of claim 14, wherein the precoding matrix is selected by

$W_{\mathrm{CF}}$

 

⁢

1 , k = arg ⁢

 

⁢

max i , j ⁢

r k , i , j ,

where r_k,i,j is a received SNR of a kth terminal, i is the index of precoding matrix, and j is the index of a column of the preceding matrix.