Subcarrier power reallocation

• US 9,787,333 B2
• Filed: 09/13/2013
• Issued: 10/10/2017
• Est. Priority Date: 09/13/2013
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Sen, Souvik, Lee, Jung Gun, Hogan, Tom
• Primary Examiner(s): Perez, James M
• Application Number:
  US14/917,068
• Publication Number:
  US 20160218756A1
• Time in Patent Office: 1,488 Days
• Field of Search: 375259-285, 375295-315
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 2001/0416 having gain or transmission power control
• CPC Class Codes: H04B 7/0426 Power distribution
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

A first set of subcarriers having signal-to-noise ratio (SNR) values that exceed a target SNR value is identified at a transmitter. A second set of subcarriers having SNR values below the target SNR value is identified. Power is iteratively reallocated from the first and second set of subcarriers to a third set of subcarriers having SNR values below the target value but closer to the target SNR value than the second set of subcarriers.

Claims

1. A method comprising:

identifying, at a transmitter, a first set of subcarriers of a plurality of subcarriers having signal-to-noise ratio (SNR) values that exceed a target SNR value;

identifying a second set of subcarriers having SNR values below the target SNR value; and

iteratively reallocating power from the first and second set of subcarriers to a third set of subcarriers having SNR values below the target SNR value but closer to the target SNR value than the second set of subcarriers, wherein the third set of subcarriers receives the reallocated power.

2. The method of claim 1, comprising:

determining a minimum number of subcarriers to achieve the target SNR value for delivery of a signal from the transmitter to a receiver using a predetermined modulation and coding rate prior to iteratively reallocating power; and

iteratively reallocating power from the first and second set of subcarriers to the third set of subcarriers until at least the minimum number of subcarriers is reached.

3. The method of claim 2, wherein the predetermined modulation and coding rate is selected by iteratively increasing a modulation and coding rate until a highest modulation and coding rate is reached that supports the target SNR value.

4. The method of claim 2, wherein the iterative reallocation is performed such that the first set of subcarriers are left with SNR values that are at least equal to the target SNR value, and wherein the iterative reallocation is performed such that at least one of the third set of subcarriers achieves an SNR value that is at least equal to the target SNR value.

5. The method of claim 1, wherein one antenna of a plurality of antennas of the transmitter is allocated per subcarrier of the plurality of subcarriers.

6. The method of claim 1, wherein iteratively reallocating power includes iteratively reallocating power from the first set of subcarriers before reallocating power from the second set of subcarriers.

7. The method of claim 1, wherein identifying the second set of subcarriers includes determining subcarriers that cannot meet the target SNR value even when power is reallocated to such subcarriers.

8. The method of claim 1, wherein the iterative reallocation is performed until there are no more subcarriers in the first and second set of subcarriers to reallocate power from, and wherein the iterative reallocation is performed until there are no more subcarriers in the third set of subcarriers to reallocate power to.

9. A wireless transmitter comprising:

a plurality of antennas to transmit a signal from the transmitter to a receiver, wherein the signal is encoded on a plurality of subcarriers, and wherein at least one antenna is allocated to at least one subcarrier; and

a controller to;

determine a minimum number of subcarriers to achieve a target signal-to-noise ratio (SNR) value for delivery of the signal using a predetermined modulation and coding rate;

identify a first set of subcarriers of a plurality of subcarriers having SNR values that exceed the target SNR value;

identify a second set of subcarriers having SNR values that are below the target SNR value; and

iteratively reallocate power from the first and second set of subcarriers to a third set of subcarriers having SNR values that are below the target SNR value but closer to the target SNR value than the second set of subcarriers, until at least the minimum number is reached.

10. The wireless transmitter of claim 9, wherein power is iteratively reallocated from the first set of subcarriers before being iteratively reallocated from the second set of subcarriers, and wherein a total transmit power of the transmitter is fixed.

11. The wireless transmitter of claim 9, the controller to perform the iterative reallocation of power according to a maximization function:

maximize F(M,C) such that P_U>

Σ

_i=1^KP_i,j≧

0 and Σ

_i=1^KΣ

_j=1^NP_i,j≦

P_T,

wherein K is a number of the plurality of antennas,

wherein N is a number of total subcarriers,

wherein P_i,j is an amount of power allocated from antenna i of the plurality of antennas to subcarrier j of the plurality of subcarriers,

wherein P_T is the total allowed transmit power,

wherein P_U is a maximum amount of power that can be allocated to any subcarrier from the plurality of antennas, and

wherein M is the modulation and C is the coding rate of the function F.

12. The wireless transmitter of claim 11, wherein when one antenna of the plurality of antennas is to be allocated per subcarrier, the controller to perform the iterative reallocation according to a maximization solution of:

13. The wireless transmitter of claim 9, wherein the wireless transmitter utilizes orthogonal frequency division multiplexing (OFDM) transmission standard.

14. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processor of a wireless transmitter, causes the processor to:

determine a minimum number of subcarriers to achieve a target signal-to-noise ratio (SNR) value for delivery of a signal using a particular modulation and coding rate;

identify a first set of subcarriers of a plurality of subcarriers having SNR values that exceed the target SNR value;

identify a second set of subcarriers having SNR values that are below the target SNR value; and

iteratively reallocate power from the first and second set of subcarriers to a third set of subcarriers having SNR values that are below the target SNR value but closer to the target SNR value than the second set of subcarriers, until at least the minimum number of subcarriers is reached, wherein the third set of subcarriers receives the reallocated power.

15. The non-transitory computer-readable storage medium of claim 14, wherein power is iteratively reallocated from the first set of subcarriers before being iteratively reallocated from the second set of subcarriers, and wherein a total transmission power of the transmitter is fixed.

16. The non-transitory computer-readable storage medium of claim 14, wherein the predetermined modulation and coding rate is selected by iteratively increasing a modulation and coding rate until a highest modulation and coding rate is reached that supports the target SNR value.

17. The non-transitory computer-readable storage medium of claim 14, wherein the iterative reallocation is performed such that the first set of subcarriers are left with SNR values that are at least equal to the target SNR value, and wherein the iterative reallocation is performed such that at least one of the third set of subcarriers achieves an SNR value that is at least equal to the target SNR value.

18. The non-transitory computer-readable storage medium of claim 14, wherein one antenna of a plurality of antennas of the transmitter is allocated per subcarrier of the plurality of subcarriers.

19. The non-transitory computer-readable storage medium of claim 14, wherein identifying the second set of subcarriers includes determining subcarriers that cannot meet the target SNR value even when power is reallocated to such subcarriers.

20. The non-transitory computer-readable storage medium of claim 14, wherein the iterative reallocation is performed until there are no more subcarriers in the first and second set of subcarriers to reallocate power from, and wherein the iterative reallocation is performed until there are no more subcarriers in the third set of subcarriers to reallocate power to.