System and Method for Transparent Coordinated Beam-Forming

• US 20120202431A1
• Filed: 04/12/2012
• Published: 08/09/2012
• Est. Priority Date: 06/15/2010
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Jia, Ming, Ma, Jianglei, Hawryluck, Mark Andrew
• Granted Patent: US 9,077,413 B2
• Time in Patent Office: Days
• US Class Current: 455/63.4
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• 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
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04W 52/143 Downlink power control
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff

Abstract

A method for reducing interference at a first user equipment (UE) includes receiving, by a second communications controller, a request to reduce interference at the first UE, the first UE being served by a first communications controller. The method also includes determining, by the second communications controller, a beam adjustment in accordance with uplink transmission measurements of the first UE and a second UE, the beam adjustment to aim a transmission to the second UE away from the second UE and towards an angle orthogonal to a first direction of the first UE relative to the second communications controller, the second UE being served by the second communications controller. The method further includes pre-adjusting, by the second communications controller, the transmission with the beam adjustment, and transmitting, by the second communications controller, the pre-adjusted transmission to the second UE.

Claims

1. A method for reducing interference at a first user equipment (UE), the method comprising:

receiving, by a second communications controller, a request to reduce interference at the first UE, the first UE being served by a first communications controller;

determining, by the second communications controller, a beam adjustment in accordance with uplink transmission measurements of the first UE and a second UE, the beam adjustment to aim a transmission to the second UE away from the second UE and towards an angle orthogonal to a first direction of the first UE relative to the second communications controller, the second UE being served by the second communications controller;

pre-adjusting, by the second communications controller, the transmission with the beam adjustment; and

transmitting, by the second communications controller, the pre-adjusted transmission to the second UE.

2. The method of claim 1, wherein determining the beam adjustment comprises:

generating a first uplink channel characteristic of the first UE from the uplink transmission measurements of the first UE;

generating a second uplink channel characteristic of the second UE from the uplink transmission measurements of the second UE;

estimating the first direction of the first UE relative to the second communications controller according to the first uplink channel characteristic of the first UE;

estimating a second direction of the second UE relative to the second communications controller according to the second uplink channel characteristic of the second UE; and

determining the beam adjustment in accordance with the first direction of the first UE and the second direction of the second UE.

3. The method of claim 2, wherein pre-adjusting the transmission comprises adjusting a precoder of the transmission according to the beam adjustment.

4. The method of claim 1, wherein the beam adjustment comprises at least one of a rotation matrix, a scaled rotation matrix, a rotation matrix multiplied by a factor, a masked rotation matrix, a rotation matrix masked by an antenna selection mask, an approximation of a rotation matrix, and a combination thereof.

5. The method of claim 1, wherein the beam adjustment comprises a diagonal matrix.

6. The method of claim 5, wherein the first communications controller includes co-polarized antennas, and wherein determining the beam adjustment comprises:

evaluating φ

_2,ii=u_2,i,adj^UL/u_2,i^UL, with φ

_2,ii, u_2,i,adj^UL, and u_2,i^UL being i-th diagonal elements of Φ

₂, {right arrow over (f)}_2,adj^DL, and {right arrow over (f)}₂^DL respectively, and Φ

₂ being the beam adjustment applied to a precoder of the transmission, {right arrow over (f)}_2,adj^DL being a vector representing a beam adjusted direction of the transmission to the second UE, and {right arrow over (f)}₂^DL being a vector representing a direction of the transmission to the second UE prior to the beam adjustment.

7. The method of claim 6, further comprising approximating the beam adjustment with φ

_ii=u_i,adj/u_i, with {u_i} being elements of a dominant Eigen-vector, and {u_i,adj} being elements of the angle of the precoder after adjustment.

8. The method of claim 5, wherein the first communications controller includes cross-polarized antennas, and wherein determining the beam adjustment comprises:

evaluating φ

_2,ii=u_2,i,adj^UL/u_2,i^UL, with φ

_2,ii, u_2,i,adj^UL, and u_2,i^UL being i-th diagonal elements of Φ

₂, {right arrow over (f)}_2,i,adj^DL, and {right arrow over (f)}₂^DL, respectively, and Φ

₂ being the beam adjustment applied to a precoder of the transmission, {right arrow over (f)}_2,adj^DL being a vector representing a beam adjusted direction of the transmission to the second UE, and {right arrow over (f)}₂^DL being a vector representing a direction of transmission to the second UE prior to the beam adjustment.

9. The method of claim 1, wherein pre-adjusting the transmission further comprises adjusting a transmit power level of the transmission.

10. The method of claim 9, wherein adjusting the transmit power level comprises reducing the transmit power level.

11. The method of claim 1, wherein pre-adjusting the transmission changes a direction of the transmission to the second UE so that the changed direction of the transmission is orthogonal to the direction of the first UE.

12. The method of claim 1, wherein pre-adjusting the transmission changes a direction of the transmission to the second UE so that the changed direction of the transmission is orthogonal to the direction of the first UE and is bounded by a maximum performance degradation threshold.

13. The method of claim 12, wherein the changed direction of the transmission for the second UE is not orthogonal to the first UE.

14. The method of claim 1, further comprising prior to receiving the request to reduce the interference at the first UE:

receiving a prior request to assist the first UE;

generating a prior uplink channel characteristic of the first UE from prior uplink transmission measurements of the first UE; and

estimating a prior direction of the first UE relative to the second communications controller according to the prior uplink channel characteristic of the first UE.

15. A method for reducing interference at a first user equipment (UE) served by a first communications controller, the method comprising:

identifying, by the first communications controller, the first UE as vulnerable to interference from transmissions of a neighbor communications controller to a second UE;

requesting, by the first communications controller, that the neighbor communications controller reduce the interference at the first UE by adjusting a transmission intended for the second UE away from the second UE and towards an angle orthogonal to a direction of the first UE relative to the neighbor communications controller, wherein adjusting the transmission is according to uplink transmission measurements of the first UE and uplink transmission measurements of the second UE; and

transmitting, by the first communications controller, to the first UE after the neighbor communications controller has reduced interference to the first UE.

16. The method of claim 15, wherein identifying the first UE includes locating the first UE operating near an edge of a coverage area of the first communications controller and near the neighbor communications controller.

17. The method of claim 15, further comprising requesting that the neighbor communications controller determine channel characteristics for the first UE.

18. An assisting communications controller comprising:

a receiver configured to receive a request to reduce interference at a first UE, the first UE being served by a first communications controller;

a processor operatively coupled to the receiver, the processor configured to determine a beam adjustment in accordance with uplink transmission measurements of the first UE and a second UE, the beam adjustment to aim a transmission to the second UE away from the second UE and towards an angle orthogonal to a first direction of the first UE relative to the assisting communications controller, the second UE being served by the assisting communications controller, and to pre-adjust the transmission with the beam adjustment; and

a transmitter operatively coupled to the processor, the transmitter configured to transmit the pre-adjusted transmission to the second UE.

19. The assisting communications controller of claim 18, wherein the processor is configured to generate a first uplink channel characteristic of the first UE from the uplink transmission measurements of the first UE, to generate a second uplink channel characteristic of the second UE from the uplink transmission measurements of the second UE, to estimate the first direction of the first UE relative to the assisting communications controller according to the first uplink channel characteristic of the first UE, to estimate a second direction of the second UE relative to the assisting communications controller according to the second uplink channel characteristic of the second UE, and to determine the beam adjustment in accordance with the first direction of the first UE and the second direction of the second UE.

20. The assisting communications controller of claim 19, wherein the processor is configured to adjust a transmit power level of the transmission.

21. The assisting communications controller of claim 20, wherein the processor is configured to reduce a transmit power level of the transmission.

22. The assisting communications controller of claim 18, wherein the receiver is configured to receive a prior request to assist the first UE, and wherein the processor is configured to generate a prior uplink channel characteristic of the first UE from prior uplink transmission measurements of the first UE, and to estimate a prior direction of the first UE relative to the assisting communications controller according to the prior uplink channel characteristic of the first UE.