SYSTEMS AND METHOD FOR COORDINATED MULTIPOINT DOWNLINK TRANSMISSIONS

• US 20100234053A1
• Filed: 03/16/2009
• Published: 09/16/2010
• Est. Priority Date: 03/16/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Krasny, Leonid, Zangi, Kambiz, Hui, Dennis
• Granted Patent: US 8,107,983 B2
• Time in Patent Office: Days
• US Class Current: 455/501
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems

Abstract

A method for determining antenna weights for use in transmitting data from a plurality of base stations to a user device is disclosed. The antenna weights are determined using an input covariance matrix (S), and the input covariance matrix is determined subject to a predetermined power constraint and a predetermined, non-zero interference constraint.

Claims

1. A method for transmitting data from a plurality of base stations to a user device, comprising:

determining antenna weights for each of the plurality of base stations that maximize the data rate that can be reliably transmitted to the user device subject to a predetermined power constraint and a predetermined, non-zero interference constraint; and

transmitting data the user device using the determined antenna weights.

2. The method of claim 1, wherein the step of determining the antenna weights comprises:

for the user device and each of a plurality of other user devices in communication with the plurality of base stations, determining a channel response matrix (H);

for the user device and each the plurality of other user devices, generating an interference constraint matrix (G);

using H and G for the user device, determining an input covariance matrix (S) for the user device subject to the power constraint and the interference constraint; and

using S to determine the antenna weights.

3. The method of claim 2, wherein the step of determining S subject to the power constraint and the interference constraint comprises:

selecting a variable (α

); and

using α

to compute S, wherein

the step of selecting a comprises;

(a) setting α

to an initial value;

(b) after step (a), using α

to determine a transmit power;

(c) after step (b), determining whether the determined transmit power is equal or about equal to predetermined power constraint value (P₀); and

(d) after step (c), increasing or decreasing α and

repeating steps (b) through (d) if the determined transmit power is not equal or about equal to P₀.

4. The method of claim 3, wherein the step of using α

to determine a transmit power comprises computing equation (81).

5. The method of claim 4, wherein the step of using α

to determine a transmit power further comprises computing equation (72)-(77) prior to computing equation (81).

6. The method of claim 2, wherein the step of determining S comprises:

(a) determining S subject only to the predetermined power constraint;

(b) after step (a), evaluating interference generated for the plurality of other user devices;

(c) based on the evaluated interference, determining whether the predetermined interference constraint is satisfied, wherein

steps (a)-(c) are performed prior to the step of determining S subject to the predetermined power constraint and the predetermined interference constraint.

7. The method of claim 6, wherein step (a) comprises computing equations (12) through (16).

8. The method of claim 6, wherein the step of determining S further comprises:

(d) determining whether an interference constraint matrix has a full rank in response to determining in step (c) that the predetermined interference constraint is not satisfied.

9. The method of claim 8, wherein the step of determining S subject to the predetermined power constraint and the predetermined interference constraint is performed in response to determining in step (d) that the interference constraint matrix does not have a full rank.

10. The method of claim 8, wherein the step of determining S further comprises:

(e) computing S subject only to the predetermined interference constraint; and

(f) after step (e), determining whether the power constraint is satisfied.

11. The method of claim 10, wherein the step of determining S subject to the predetermined power constraint and the predetermined interference constraint is performed in response to determining in step (f) that the power constraint is not satisfied.

12. A controller for determining antenna weights for use in transmitting data to a user device via a plurality of base stations in communication with the controller, comprising:

a transmitter and receiver for communicating with the plurality of base stations;

a data storage system; and

a data processing system, wherein the data processing system is configured to;

determine antenna weights for each of the plurality of base stations that maximize the data rate that can be reliably transmitted to the user device subject to a predetermined power constraint and a predetermined, non-zero interference constraint; and

cause the data to be transmitted to the user device using the determined antenna weights.

13. The controller of claim 12, wherein the data processing system is configured to determine the antenna weights by:

determining a channel response matrix (H) for the user device and each of a plurality of other user devices in communication with the plurality of base stations;

generating an interference constraint matrix (G) for the user device and each the plurality of other user devices;

determining an input covariance matrix (S) subject to the predetermined power constraint and the predetermined, non-zero interference constraint for the user device using H and G for the user device; and

using S to determine the antenna weights.

14. The controller of claim 13, wherein the data processing system is configured to determine S subject to the power constraint and the interference constraint by:

selecting a variable (α

); and

using α

to compute S, wherein

selecting α

comprises;

(a) setting α

to an initial value;

(b) after step (a), using α

to determine a transmit power;

(c) after step (b), determining whether the determined transmit power is equal or about equal to predetermined power constraint value (P₀); and

(d) after step (c), increasing or decreasing α and

repeating steps (b) through (d) if the determined transmit power is not equal or about equal to P₀.

15. The controller of claim 14, wherein the data processing system is configured to use α

to determine a transmit power by computing equation (81).

16. The controller of claim 15, wherein the data processing system is configured to use α

to determine a transmit power by computing equation (72)-(77) prior to computing equation (81).

17. The controller of claim 13, wherein the data processing system is configured to determine S by:

(a) determining S subject only to the predetermined power constraint;

(b) after (a), evaluating interference generated for the plurality of other user devices;

(c) based on the evaluated interference, determining whether the predetermined interference constraint is satisfied, wherein

the data processing system is configured to perform steps (a)-(c) prior to determining S subject to the predetermined power constraint and the predetermined interference constraint.

18. The controller of claim 17, wherein the data processing system is configured to perform step (a) by computing equations (12) through (16).

19. The controller of claim 17, wherein the data processing system is configured to determine S by:

(d) determining whether an interference constraint matrix has a full rank in response to determining in step (c) that the predetermined interference constraint is not satisfied.

20. The controller of claim 19, wherein the data processing system is configured to determine S subject to the predetermined power constraint and the predetermined interference constraint in response to determining that the interference constraint matrix does not have a full rank.

21. The controller of claim 19, wherein the data processing system is configured to determine S by further:

(e) computing S subject only to the predetermined interference constraint; and

(f) after (e), determining whether the power constraint is satisfied.

22. The controller of claim 21, wherein the data processing system is configured to determine S subject to the predetermined power constraint and the predetermined interference constraint in response to determining that the power constraint is not satisfied.