Transmit correlated array gain reduction

• US 9,112,555 B2
• Filed: 11/16/2012
• Issued: 08/18/2015
• Est. Priority Date: 11/16/2012
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Silverman, Matthew A., Stager, Paul J., Nicholson, James C.
• Primary Examiner(s): FILE, ERIN M
• Application Number:
  US13/678,849
• Publication Number:
  US 20140140438A1
• Time in Patent Office: 1,005 Days
• Field of Search: 375/299
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0426 Power distribution
• CPC Class Codes: H04B 7/0602 using antenna switching H04B7/0686 takes precedence; antenna beam directivity switching H01Q3/24
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Techniques are presented herein to achieve reduced array gain associated with a transmission made from multiple antennas of a wireless communication device. In accordance with one technique, a wireless communication device is provided having a plurality of transmitters each configured to transmit via a corresponding one of a plurality of antennas. Subcarriers of at least one transmit signal to be weighted across the plurality of transmitters are allocated power so that for each subcarrier, only one transmitter is allocated a maximum power.

Claims

1. A method comprising:

at a wireless communication device having a plurality of transmitters each configured to transmit via a corresponding one of a plurality of antennas;

dividing subcarriers of at least one transmit signal into groups;

allocating power to the groups of the subcarriers of the at least one transmit signal to be weighted across the plurality of transmitters for transmission; and

applying a precoding matrix for each subcarrier so that for each subcarrier, only one transmitter is allocated a maximum power and no beamforming occurs per subcarrier.

2. The method of claim 1, wherein for four antennas, allocating comprises applying a precoding matrix V_k for subcarrier k, where for any arbitrary four contiguous subcarriers,

V_k=

V_—

1=[1 0 0 0]^T

V_—

2=[0 1 0 0]^T

V_—

3=[0 0 1 0]^T

V_—

4=[0 0 0 1]T.

3. The method of claim 1, further comprising dividing the subcarriers of the at least one transmit signal into groups of subcarriers, and allocating power for groups of subcarriers to a corresponding one of the plurality of transmitters.

4. The method of claim 3, wherein allocating comprises applying a precoding matrix V_k for subcarrier k, where V_k=

V_(1:

numSc/4)=[1 0 0 0]^T

V_(numSc/4+1;

2*numSc/4)=[0 1 0 0]^T

V_(2*numSc/4+1;

3*numSc/4)=[0 0 1 0]^T

V_(3*numSc/4+1;

numSc)=[0 0 0 1]^T,

where numSc is the number of subcarriers of the at least one transmit signal.

5. A method comprising:

at a wireless communication device having a plurality of transmitters each configured to transmit via a corresponding one of a plurality of antennas;

dividing subcarriers of M plurality of transmit signals into groups;

allocating power to the groups of the subcarriers of the M plurality of the transmit signals for simultaneous transmission by the plurality of transmitters based on a number of subcarriers of the M plurality of transmit signals; and

applying precoding matrices for each subcarrier so that for each subcarrier, only M transmitters are allocated maximum power and no beamforming occurs per subcarrier.

6. The method of claim 5, wherein when M=2 and the number of antennas is four, allocating comprises applying precoding matrices:

V_—

1=[[1 1 0 0]^T [1 −

1 0 0]^T]

V_—

2=[[0 0 1 1]^T [0 0 1 −

1]T].

7. An apparatus comprising:

a plurality of transmitters and a corresponding plurality of antennas; and

a baseband processor configured to be coupled to the plurality of transmitters, wherein the baseband processor is configured to;

divide subcarriers of at least one transmit signal into groups;

allocate power to the groups of the subcarriers of the at least one transmit signal to be weighted across the plurality of transmitters for transmission; and

apply a precoding matrix for each subcarrier so that for each subcarrier, only one transmitter is allocated a maximum power and no beamforming occurs per subcarrier.

8. The apparatus of claim 7, wherein for four antennas, the baseband processor is configured to apply a precoding matrix V_k for subcarrier k, where for any arbitrary four contiguous subcarriers, V_k=

V_—

1=[1 0 0 0]^T

V_—

2=[0 1 0 0]^T

V_—

3=[0 0 1 0]^T

V_—

4=[0 0 0 1]^T.

9. The apparatus of claim 7, wherein the baseband processor is configured to divide the subcarriers of the at least one transmit signal into groups of subcarriers, and allocate power for groups of subcarriers to a corresponding one of the plurality of transmitters.

10. The apparatus of claim 9, wherein the baseband processor is configured to apply a precoding matrix V_k for subcarrier k, where V_k=

V_(1:

numSc/4)=[1 0 0 0]^T

V_(numSc/4+1;

2*numSc/4)=[0 1 0 0]^T

V_(2*numSc/4+1;

3*numSc/4)=[0 0 1 0]^T

V_(3*numSc/4+1;

numSc)=[0 0 0 1]^T,

where numSc is the number of subcarriers of the at least one transmit signal.

11. An apparatus comprising:

a plurality of transmitters and a corresponding plurality of antennas; and

a baseband processor configured to be coupled to the plurality of transmitters, wherein the baseband processor is configured to;

divide subcarriers of M plurality of transmit signals into groups;

allocate power to the groups of the subcarriers of the M plurality of transmit signals for simultaneous transmission by the plurality of transmitters; and

apply precoding matrices for each subcarrier so that for each subcarrier, only M transmitters are allocated maximum power and no beamforming occurs per subcarrier.

12. The apparatus of claim 11, wherein when M=2 and the number of antennas is 4, the baseband processor is configured to apply the precoding matrices:

V_—

1=[[1 1 0 0]^T [1 −

1 0 0]^T]

V_—

2=[[0 0 1 1]^T [0 0 1 −

1]T].

13. One or more non-transitory computer readable storage media encoded with software comprising computer executable instructions and when the software is executed operable to:

queue at least one transmit signal for transmission, the at least one transmit signal comprising a plurality of subcarriers;

divide subcarriers of at least one transmit signal into groups; and

allocate power to the groups of the subcarriers of the at least one transmit signal to be weighted across the plurality of transmitters for transmission; and

apply a precoding matrix for each subcarrier so that for each subcarrier, only one transmitter is allocated a maximum power and no beamforming occurs per subcarrier.

14. The non-transitory computer readable storage media of claim 13, wherein for four antennas, the instructions operable to allocate comprises instructions operable to apply a precoding matrix V_k for subcarrier k, where for any arbitrary four contiguous subcarriers,

V_k=

V_—

1=[1 0 0 0]^T

V_—

2=[0 1 0 0]^T

V_—

3=[0 0 1 0]^T

V_—

4=[0 0 0 1]^T.

15. The non-transitory computer readable storage media of claim 13, further comprising instructions operable to divide the subcarriers of the at least one transmit signal into groups of subcarriers, and wherein the instructions operable to allocate comprises instructions operable to allocate power for groups of subcarriers to a corresponding one of the plurality of transmitters.

16. The non-transitory computer readable storage media of claim 15, wherein the instructions operable to allocate comprises instructions operable to apply a precoding matrix V_k for subcarrier k, where V_k=

V_(1:

numSc/4)=[1 0 0 0]^T

V_(numSc/4+1;

2*numSc/4)=[0 1 0 0]^T

V_(2*numSc/4+1;

3*numSc/4)=[0 0 1 0]^T

V_(3*numSc/4+1;

numSc)=[0 0 0 1]^T,

where numSc is the number of subcarriers of the at least one transmit signal.

17. One or more non-transitory computer readable storage media encoded with software comprising computer executable instructions and when the software is executed operable to:

queue at least one transmit signal for transmission, the at least one transmit signal comprising a plurality of subcarriers;

divide subcarriers of M plurality of transmit signals into groups;

allocate power to the groups of the subcarriers of the M plurality of transmit signals for simultaneous transmission by a plurality of transmitters; and

apply a precoding matrix for each subcarrier so that for each subcarrier, only M transmitters are allocated maximum power and no beamforming occurs per subcarrier.

18. The non-transitory computer readable storage media of claim 17, wherein when M=2 and the number of antennas is four, the instructions operable to allocate comprise instructions operable to apply precoding matrices:

V_—

1=[[1 1 0 0]^T [1 −

1 0 0]^T]

V_—

2=[[0 0 1 1]^T [0 0 1 −

1]T].