UPLINK NOISE ESTIMATION FOR VIRTUAL MIMO

• US 20140064391A1
• Filed: 10/11/2010
• Published: 03/06/2014
• Est. Priority Date: 10/11/2010
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Xu, Changlong, Yang, Xuebin, Zhou, Feng, Gao, Yang, Cheng, Peng
• Granted Patent: US 9,008,207 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 17/345 Interference values signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] H04B17/336
• 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 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04L 25/03197 methods of calculation involving metrics

Abstract

A system and methods for estimating a noise power level in an uplink signal for a virtual MIMO system is disclosed. The system comprises a demodulation reference signal (DMRS) module configured to obtain a DMRS receive symbol from the uplink signal and determine a DMRS sequence for a first UE in the virtual MIMO system. An autocorrelation module is configured to calculate an average autocorrelation value for the subcarriers in the uplink signal. A cross-correlation module is configured to calculate first and second cross-correlation values of the uplink signal R_z (l) for values of l selected such that the sum of the received power from the first UE and the second UE can be accurately estimated. A noise power level module is configured to determine the noise power level for the uplink signal using the average autocorrelation value and the first and second cross correlation values.

Claims

1. A method for estimating noise power in an uplink signal for a virtual multiple input multiple output (MIMO) system including a first user equipment (UE) and a second UE, comprising:

obtaining a demodulation reference signal (DMRS) receive symbol in the uplink signal;

determining a DMRS sequence for the first user equipment (UE) in the virtual MIMO system using a correlation calculation;

calculating an average autocorrelation value for N subcarriers in the uplink signal, wherein N is a total number of subcarriers in the uplink signal;

calculating a first cross-correlation value R_z (l) of the uplink signal for a first value of l using the DMRS sequence for the first UE;

calculating a second cross-correlation value R_z (l) of the uplink signal for a second value of l using the DMRS sequence for the first UE, wherein the first and second values of l are selected such that the sum of the two UEs'"'"' received power can be accurately estimated; and

determining the noise power level for the uplink signal in the virtual MIMO system using the average autocorrelation value and the first and second cross correlation values.

2. The method of claim 1, wherein obtaining the DMRS receive symbol further comprises obtaining the DRMS receive symbol at the m^th symbol on the n^th subcarrier, where m is a positive integer and n is an integer value between 1 and N.

3. The method of claim 1, further comprising selecting the first value of l as 12 and selecting the second value of l as 24.

4. The method of claim 1, further comprising selecting the first value of l and the second value of l such that the ratio of

5. The method of claim 1, wherein calculating the average autocorrelation value for the N subcarriers further comprises calculating the average autocorrelation value R_Y(0) using:

6. The method of claim 5, wherein calculating the first cross-correlation value further comprises calculating the cross correlation value multiplied by an autocorrelation of the DMRS sequence using:

7. The method of claim 6, wherein calculating the second cross correlation value further comprises calculating the cross correlation value multiplied by the autocorrelation of the DMRS sequence using:

8. The method of claim 7, further comprising determining noise power W for the uplink signal in the virtual MIMO system using:

9. A method for estimating noise power in an uplink signal for a virtual multiple input multiple output (MIMO) system including a first user equipment (UE) and a second UE, comprising:

obtaining a demodulation reference signal (DMRS) receive symbol in the uplink signal at an m^th symbol on an n^th subcarrier, where m is a positive integer and n is an integer value between 1 and N and N is a total number of subcarriers in the uplink signal;

determining a DMRS sequence for the first UE in the virtual MIMO system using a correlation calculation;

calculating an average autocorrelation value for the N subcarriers;

calculating a first cross-correlation value R_Z (12) for every 12^th subcarrier in the uplink signal using the DMRS sequence for the first UE;

calculating a second cross-correlation value R_Z (24) for every 24^th subcarrier in the uplink signal using the DMRS sequence for the first UE; and

determining the noise power for the uplink signal in the virtual MIMO system using the average autocorrelation value and the first and second cross correlation values.

10. The method of claim 9, further comprising determining a signal power of the uplink signal for the first UE and the second UE in the virtual MIMO system using the first and second cross-correlation values.

11. The method of claim 9, wherein calculating the average autocorrelation value for the N subcarriers further comprises calculating the average autocorrelation value R_Y(0) using:

12. The method of claim 11, wherein calculating the first cross-correlation value further comprises calculating the cross correlation value multiplied by an autocorrelation of the DMRS sequence using:

13. The method of claim 12, wherein calculating the second cross correlation value further comprises calculating the cross correlation value multiplied by the autocorrelation of the DMRS sequence using:

14. The method of claim 13, further comprising determining a signal power S₁P₁+S₂P₂ of the uplink signal using:

15. The method of claim 14, further comprising determining noise power W for the uplink signal in the virtual MIMO system using:

W=R_Y(0)−

(S₁P₁+S₂P₂).

16. The method of claim 13, further comprising determining noise power W for the uplink signal in the virtual MIMO system using:

17. A system for estimating a noise power level in an uplink signal for a virtual MIMO system including a first user equipment (UE) and a second UE, comprising:

a demodulation reference signal (DMRS) module configured to obtain a DMRS receive symbol from the uplink signal and determine a DMRS sequence for the first UE in the virtual MIMO system using a correlation calculation;

an autocorrelation module configured to calculate an average autocorrelation value for N subcarriers in the uplink signal, wherein N is a total number of subcarriers in the uplink signal;

a cross-correlation module configured to calculate first and second cross-correlation values R_z (l) of the uplink signal for a first value of l and a second value of l, respectively, using the DMRS sequence for the first UE, wherein the first and second values of l are selected such that the sum of the received power from the first UE and the second UE can be accurately estimated; and

a noise power level module configured to determine the noise power level for the uplink signal in the virtual MIMO system using the average autocorrelation value and the first and second cross correlation values.

18. The system of claim 17, wherein the autocorrelation module is further configured to calculate the average autocorrelation value R_Y(0) using:

19. The system of claim 17, wherein the cross-correlation module is further configured to select the first value of l and the second value of l such that the ratio of

20. The system of claim 18, wherein the cross-correlation module is further configured to calculate the first cross correlation value for l=12 as a cross correlation multiplied by an autocorrelation of the DMRS sequence for every 12^th subcarrier using:

21. The system of claim 20, wherein the cross-correlation module is further configured to calculate the second cross correlation value for l=24 as a cross correlation multiplied by the autocorrelation of the DMRS sequence using:

22. The system of claim 21, wherein the noise power level module is further configured to determine noise power W for the uplink signal in the virtual MIMO system using: