Method and apparatus for reverse link transmit beam-forming

• US 7,729,714 B2
• Filed: 12/20/2005
• Issued: 06/01/2010
• Est. Priority Date: 12/20/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Tokgoz, Yeliz, Black, Peter John, Fan, Mingxi
• Primary Examiner(s): SHARMA, SUJATHA R
• Application Number:
  US11/313,320
• Publication Number:
  US 20070142074A1
• Time in Patent Office: 1,624 Days
• Field of Search: 455/562.1, 455/561, 455/522, 455/442, 455/78, 455/101, 455/447, 455/450, 455/509, 455/67.16, 455/67.11, 455/126, 455/69, 455/13.4, 455/452.2, 455/422.1, 370/252, 370332-334, 370/328
• US Class Current: 455/522
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
• 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 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0404 the mobile station comprising multiple antennas, e.g. to provide uplink diversity
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0623 Auxiliary parameters, e.g. power control [PCB] or not acknowledged commands [NACK], used as feedback information
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A method and system for reverse link transmit beam-forming. One method comprises using a plurality of antennas at an access terminal to wirelessly transmit signals to one or more base stations; receiving an input indicating a reverse link signal quality at the one or more base stations; and adjusting at least one of a gain and a phase of a signal to be transmitted on one or more antennas. The input may be a reverse power control (RPC) value sent from one or more base stations or a measurement of the closed-loop pilot transmit power.

Claims

1. An access terminal comprising:

a plurality of antennas configured to wirelessly transmit signals to one or more base stations; and

a coefficient adaptation control unit configured to receive a reverse power control (RPC) value sent from one or more base stations and adjust at least one of a gain and a phase of a signal to be transmitted on one or more antennas until the RPC value is close to zero.

2. The access terminal of claim 1, wherein the access terminal further comprises a RPC filter function configured to receive RPC bits sent from multiple base stations and output a filtered RPC value to the coefficient adaptation control unit.

3. The access terminal of claim 2, wherein the RPC filter function determines the filtered RPC value as:

filtRPC(n)=(1−

α

)filtRPC(n−

1)+α

·

ƒ

(RPC₀(n),RPC₁(n), . . . , RPC_L(n))

where α

denotes a constant for an infinite impulse response filter, filtRPC(n−

1) denotes a filtered RPC of a previous time slot (n−

1), RPC_i(n) denotes a RPC bit received at current slot n from the ith cell in an active set of base stations, and ƒ

(RPC₀(n), . . . RPC_L(n)) denotes an effective RPC.

4. The access terminal of claim 3, wherein the effective RPC comprises a logical OR function of all RPC bits sent from base stations in the access terminal'"'"'s active set.

5. The access terminal of claim 3, wherein the effective RPC comprises a RPC bit sent from only a serving sector of the access terminal.

6. The access terminal of claim 2, wherein the RPC filter function determines the filtered RPC value as:

$\mathrm{filtRPC}<br><br><br><br>\left(n\right)=\underset{k=1}{\overset{\mathrm{UpdatePeriod}}{\sum <br><br>}}<br><br>\mathrm{AccumRPC}<br><br>\left(k,n\right)$

where

$\mathrm{AccumRPC}<br><br><br><br>\left(k,n\right)=\underset{i=1}{\overset{k}{\sum <br><br>}}<br><br>\mathrm{EffRPC}<br><br><br><br>\left(\left(n-1\right)·<br><br>\mathrm{UpdatePeriod}+i\right),<br><br>k\le <br><br>\mathrm{UpdatePeriod}.$

7. The access terminal of claim 1, wherein the input comprises a measurement of transmit pilot power.

8. The access terminal of claim 1, wherein the input comprises a transmit gain adjust value.

9. The access terminal of claim 1, wherein the coefficient adaptation control unit is configured to continuously adjust at least one of the gain and the phase of the signal to be transmitted on one or more antennas using a Least Means Square (LMS) algorithm.

10. The access terminal of claim 1, wherein the input comprises reverse power control (RPC) bits of active cells, the coefficient adaptation control unit being configured to adjust the phase of the signal to be transmitted on one or more antennas by:

θ

(n)=θ

(n−

1)+μ

·

z(n−

1), where μ

is the PhaseStep; and

{0, if filtRPC(n−

1)=filtRPC(n−

2)

z(n−

1)={−

sign(θ

(n−

1)−

θ

(n−

2)), if filtRPC(n−

1)>

filtRPC(n−

2)

{+sign(θ

(n−

1)−

θ

(n−

2)), if filtRPC(n−

1)<

filtRPC(n−

2).

11. The access terminal of claim 1, wherein the input comprises measured mean transmit pilot power, the coefficient adaptation control unit being configured to adjust the phase of the signal to be transmitted on one or more antennas by:

θ

(n)=θ

(n−

1)+μ

·

z(n−

1), where μ

is the PhaseStep; and

{0, if MeanTxPilotPower(n−

1)=MeanTxPilotPower(n−

2)

z(n−

1)={−

sign(θ

(n−

1)−

θ

(n−

2)), if MeanTxPilotPower(n−

1)>

MeanTxPilotPower(n−

2)

{+sign(θ

(n−

1)−

θ

(n−

2)), if MeanTxPilotPower(n−

1)<

MeanTxPilotPower(n−

2).

12. The access terminal of claim 1, wherein the coefficient adaptation control unit is configured to periodically adjust at least one of the gain and the phase of the signal to be transmitted on one or more antennas.

13. The access terminal of claim 12, wherein the coefficient adaptation control unit is configured to (a) for each time period, apply a phase difference between two or more antennas, (b) determine a mean transmit pilot power during each time period, and (c) after using a discrete set of phase differences, select the phase difference with a least mean transmit pilot power and use that phase difference.

14. The access terminal of claim 12, wherein the coefficient adaptation control unit is configured to (a) for each time period, apply a gain difference between two or more antennas, (b) determine a mean transmit pilot power during each time period, and (c) after using a discrete set of gain differences, select the gain difference with a least mean transmit pilot power and use that gain difference.

15. The access terminal of claim 1, further comprising a plurality of multipliers, each multiplier being coupled to the coefficient adaptation control unit and a designated signal path of one of the antennas, each multiplier being configured to multiply a complex gain coefficient from the coefficient adaptation control unit by a signal of the designated signal path.

16. A method comprising:

using a plurality of antennas at an access terminal to wirelessly transmit signals to one or more base stations;

receiving a reverse power control (RPC) value sent from one or more base stations; and

adjusting at least one of a gain and a phase of a signal to be transmitted on one or more antennas until the RPC value is close to zero.

17. The method of claim 16, further comprising:

receiving RPC bits sent from multiple base stations; and

generating a filtered RPC value based on the received RPC bits sent from multiple base stations.

18. A method of beam-forming using antennal selection, the method comprising:

wirelessly transmitting a signal on a first antenna for a first period of time;

wirelessly transmitting the signal on a second antenna for a subsequent period of time;

observing at least one of (a) reverse power control (RPC) bits sent from one or more base stations and (b) closed loop mean transmit pilot power measured during each period;

selecting the antenna that is associated with a lower closed loop mean transmit pilot power; and

using the selected antenna for a second period longer than the first period.

19. An access terminal comprising:

a plurality of antenna means configured to wirelessly transmit signals to one or more base stations; and

coefficient adaptation control means configured to receive a reverse power control (RPC) value sent from one or more base stations and adjust at least one of a gain and a phase of a signal to be transmitted on one or more antennas until the RPC value is close to zero.

20. A computer-readable storage medium having instructions thereon, the instructions comprising:

code for receiving a reverse power control (RPC) value sent from one or more base stations; and

code for adjusting at least one of a gain and a phase of a signal to be transmitted on one or more antennas until the RPC value is close to zero.