Method and apparatus for optimum selection of MIMO and interference cancellation

• US 20060285585A1
• Filed: 06/15/2006
• Published: 12/21/2006
• Est. Priority Date: 06/16/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sampath, Hemanth
• Granted Patent: US 8,064,837 B2
• Time in Patent Office: Days
• US Class Current: 375/227
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0817 with multiple receivers and antenna path selection
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 25/0204 of multiple channels

Abstract

Systems and methodologies are described that facilitate performing interference nulling and rank prediction in an access terminal. Multiple receiver demodulator types may be implemented at the access terminal, and an interference covariance matrix may be estimated thereat. SNRs may be calculated for the various receiver demodulator types, and an optimum rank and associated CQI information may be identified and generated, respectively, which information may then be transmitted to an access point. At least one of the receiver demodulator types may perform an interference nulling protocol. For example, the receiver demodulator types may comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator, along with and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

Claims

1. A method of performing interference nulling and rank prediction in an access terminal, comprising:

employing multiple receiver demodulator types at the access terminal;

estimating an interference covariance matrix;

calculating a signal-to-noise ratio (SNR) for a plurality of the multiple receiver demodulator types;

determining an optimum rank and associated channel quality index (CQI) information across all receiver demodulator types to optimize transmission capacity; and

transmitting the rank and CQI information to an access point;

wherein at least one of the receiver demodulator types performs an interference nulling technique.

2. The method of claim 1, wherein the receiver demodulator types comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

3. The method of claim 1, wherein determining an optimum rank and associated CQI information further comprises determining an effective SNR for one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNRs, selecting a rank that optimizes capacity based on the capacity numbers, and generating CQI information by quantizing the effective SNR corresponding to the selected rank.

4. The method of claim 3, further comprising estimating an average interference nulling gain, employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator, determining an optimum rank for and associated CQI information across the at least one MRC receiver demodulator and the at least one MMSE receiver demodulator, and transmitting the optimum rank and CQI information to an access point.

5. The method of claim 4, wherein estimating the average interference nulling gain further comprises determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types, determining a delta-effective SNR by computing a difference between effective SNRs for receiver demodulator types that employ interference nulling and receiver demodulator types that do not employ interference nulling, and determining the average interference nulling gain by averaging the delta-effective SNR over a plurality of time slots and tones.

6. The method of claim 5, wherein employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator further comprises determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types that do not incorporate interference nulling, adding the average interference nulling gains to the effective SNR values for the one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNR values, selecting a rank that optimizes capacity, and generating CQI information by quantizing the effective SNR corresponding to the selected rank.

7. An apparatus that facilitates performing interference nulling and rank prediction using hypothesis decoding in an access terminal, comprising:

a receiver with multiple receiver demodulators at the access terminal;

a processor that estimates an interference covariance matrix, calculates a signal-to-noise ratio (SNR) for a plurality of the multiple receiver demodulators, and determines an optimum rank and associated channel quality index (CQI) information across all receiver demodulators to optimize transmission capacity; and

a transmitter that transmits the rank and CQI information to an access point;

wherein at least one of the receiver demodulators employs an interference nulling technique.

8. The apparatus of claim 7, wherein the receiver demodulators comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

9. The apparatus of claim 7, wherein the processor determines an optimum rank and associated CQI information by determining an effective SNR for one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNRs, selecting a rank that optimizes capacity based on the capacity numbers, and generating CQI information by quantizing the effective SNR corresponding to the selected rank.

10. The apparatus of claim 9, wherein the processor estimates an average interference nulling gain, employs the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator, and determines an optimum rank for and associated CQI information across the at least one MRC receiver demodulator and the at least one MMSE receiver demodulator.

11. The apparatus of claim 10, wherein the processor estimates the average interference nulling gain by determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulators, determining a delta-effective SNR by computing a difference between effective SNRs for receiver demodulators that employ interference nulling and receiver demodulators that do not employ interference nulling, and calculating the average interference nulling gain by averaging the delta-effective SNR over a plurality of time slots and tones.

12. The apparatus of claim 11, wherein the processor employs the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator by determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types that do not incorporate interference nulling, adding the average interference nulling gains to the effective SNR values for the one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNR values, selecting a rank that optimizes capacity, and generating CQI information by quantizing the effective SNR corresponding to the selected rank.

13. An apparatus that facilitates performing interference nulling and rank prediction in an access terminal, comprising:

means for employing multiple receiver demodulator types at the access terminal;

means for estimating an interference covariance matrix;

means for calculating a signal-to-noise ratio (SNR) for a plurality of the multiple receiver demodulator types;

means for determining an optimum rank and associated channel quality index (CQI) information across all receiver demodulator types to optimize transmission capacity; and

means for transmitting the rank and CQI information to an access point;

wherein at least one of the receiver demodulator types performs an interference nulling technique.

14. The apparatus of claim 13, wherein the receiver demodulator types comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

15. The apparatus of claim 13, wherein the means for determining an optimum rank and associated CQI information determines an effective SNR for one or more candidate MIMO transmission ranks, generates capacity numbers corresponding to the effective SNRs, selects a rank that optimizes capacity based on the capacity numbers, and generates CQI information by quantizing the effective SNR corresponding to the selected rank.

16. The apparatus of claim 15, further comprising means for estimating an average interference nulling gain, means for employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator, and means for determining an optimum rank for and associated CQI information across the at least one MRC receiver demodulator and the at least one MMSE receiver demodulator.

17. The apparatus of claim 16, wherein the means for estimating the average interference nulling gain determines an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types, determines a delta-effective SNR by computing a difference between effective SNRs for receiver demodulator types that employ interference nulling and receiver demodulator types that do not employ interference nulling, and calculates the average interference nulling gain by averaging the delta-effective SNR over a plurality of time slots and tones.

18. The apparatus of claim 17, wherein the means for employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator determines an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types that do not incorporate interference nulling, adds the average interference nulling gains to the effective SNR values for the one or more candidate MIMO transmission ranks, generates capacity numbers corresponding to the effective SNR values, selects a rank that optimizes capacity, and generates CQI information by quantizing the effective SNR corresponding to the selected rank.

19. A computer-readable medium that stores computer-executable instructions for:

employing multiple receiver demodulator types at an access terminal;

estimating an interference covariance matrix;

calculating a signal-to-noise ratio (SNR) for a plurality of the multiple receiver demodulator types;

determining an optimum rank and associated channel quality index (CQI) information across all receiver demodulator types to optimize transmission capacity; and

transmitting the rank and CQI information to an access point;

wherein at least one of the receiver demodulator types performs an interference nulling technique.

20. The computer-readable medium of claim 19, wherein the receiver demodulator types comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

21. The computer-readable medium of claim 19, further comprising instructions for determining an effective SNR for one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNRs, selecting a rank that optimizes capacity based on the capacity numbers, and generating CQI information by quantizing the effective SNR corresponding to the selected rank, in order to determine the optimum rank and associated CQI information.

22. The computer-readable medium of claim 21, further comprising instructions for estimating an average interference nulling gain, employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator, and determining an optimum rank for and associated CQI information across the at least one MRC receiver demodulator and the at least one MMSE receiver demodulator.

23. The computer-readable medium of claim 22, further comprising instructions for determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types, determining a delta-effective SNR by computing a difference between effective SNRs for receiver demodulator types that employ interference nulling and receiver demodulator types that do not employ interference nulling, and determining the average interference nulling gain by averaging the delta-effective SNR over a plurality of time slots and tones, in order to estimate the average interference nulling gain.

24. The computer-readable medium of claim 23, further comprising instructions for determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types that do not incorporate interference nulling, adding the average interference nulling gains to the effective SNR values for the one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNR values, selecting a rank that optimizes capacity, and generating CQI information by quantizing the effective SNR corresponding to the selected rank, in order to employ the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator.

29. The processor of claim 22, the instructions further comprising determining an effective SNR for the one or 28 candidate MIMO transmission ranks for one or more receiver demodulator types, determining a delta-effective SNR by computing a difference between effective SNRs for receiver demodulator types that employ interference nulling and receiver demodulator types that do not employ interference nulling, and determining the average interference nulling gain by averaging the delta-effective SNR over a plurality of time slots and tones, in order to estimate the average interference nulling gain.

30. The processor of claim 29, the instructions further comprising determining an effective SNR for the one or more candidate MIMO transmission ranks for one or more receiver demodulator types that do not incorporate interference nulling, adding the average interference nulling gains to the effective SNR values for the one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNR values, selecting a rank that optimizes capacity, and generating CQI information by quantizing the effective SNR corresponding to the selected rank, in order to employ the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator.

25. A processor that executes computer-executable instructions for performing rank prediction with interference nulling, the instructions comprising:

employing multiple receiver demodulator types at an access terminal;

estimating an interference covariance matrix;

calculating a signal-to-noise ratio (SNR) for a plurality of the multiple receiver demodulator types;

determining an optimum rank and associated channel quality index (CQI) information across all receiver demodulator types to optimize transmission capacity; and

transmitting the rank and CQI information to an access point;

wherein at least one of the receiver demodulator types performs an interference nulling technique.

26. The processor of claim 25, wherein the receiver demodulator types comprise at least one minimum mean-squared error interference-nulling (MMSE-IN) demodulator and one or more of a maximal ratio combining (MRC) demodulator and a minimum mean-squared error (MMSE) demodulator.

27. The processor of claim 25, the instructions further comprising determining an effective SNR for one or more candidate MIMO transmission ranks, generating capacity numbers corresponding to the effective SNRs, selecting a rank that optimizes capacity based on the capacity numbers, and generating CQI information by quantizing the effective SNR corresponding to the selected rank, in order to determine the optimum rank and associated CQI information.

28. The processor of claim 27, the instructions further comprising estimating an average interference nulling gain, employing the estimated average nulling gain to calculate an SNR for at least one MRC receiver demodulator and at least one MMSE receiver demodulator, and determining an optimum rank for and associated CQI information across the at least one MRC receiver demodulator and the at least one MMSE receiver demodulator.