COMPUTATION OF MEASUREMENT METRICS FOR WIRELESS NETWORKS

• US 20130121187A1
• Filed: 11/07/2012
• Published: 05/16/2013
• Est. Priority Date: 11/10/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Das, Sibasish, Srinivasan, Shivratna Giri, Bhattacharjee, Supratik, Banister, Brian Clarke
• Granted Patent: US 9,185,614 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04W 24/10 Scheduling measurement reports ; Arrangements for measurement reports
• CPC Class Codes: H04W 36/0085 Hand-off measurements
• CPC Class Codes: H04W 36/0088 Scheduling hand-off measurements

Abstract

Methods and apparatus for computing measurement metrics in a wireless communications network are provided. One example method generally includes obtaining a channel impulse response (CIR) from one or more reference signals (RSs) transmitted from one or more antennas of a base station (BS); calculating an absolute square per element of the CIR to generate channel energy response (CER) elements; calculating a threshold value based on a noise variance estimated from a portion of the CER elements; selecting CER elements that exceed the threshold value; and computing a reference signal received power (RSRP) value based on the selected CER elements.

Claims

1. A method for wireless communications, comprising:

obtaining a channel impulse response (CIR) from one or more reference signals (RSs) transmitted from one or more antennas of a base station;

calculating an absolute square per element of the CIR to generate channel energy response (CER) elements;

calculating a threshold value based on a noise variance estimated from a portion of the CER elements;

selecting CER elements that exceed the threshold value; and

computing a reference signal received power (RSRP) value based on the selected CER elements.

2. The method of claim 1, wherein the base station comprises a serving base station.

3. The method of claim 2, wherein obtaining the CER elements comprises utilizing absolute square values of taps of a wideband coherently-filtered channel impulse response (CIR).

4. The method of claim 2, wherein:

the RSs are received on a plurality of receive antennas; and

obtaining the CER elements comprises summing values across transmit antennas for different receive antennas.

5. The method of claim 2, wherein the RSRP is calculated in a linear scale by accumulating selected CER elements, and further calculating the RSRP in units of dBm from the linear scale by converting to a logarithmic scale and applying appropriate normalizations.

6. The method of claim 5 wherein the RSRP is calculated by normalization based, at least in part, on a number of RS tones.

7. The method of claim 6, wherein the RSRP is calculated by normalization based, at least in part, on a number of transmit antennas and the number of RS tones.

8. The method of claim 1, further comprising:

computing a reference signal receive quality (RSRQ) value based on the computed RSRP.

9. The method of claim 8, wherein the RSRQ value is computed based, at least in part, on at least one of:

a number of resource blocks (RBs) in a downlink if the base station comprises a serving base station, and a number of RBs used for neighbor measurements if the base station comprises a neighbor base station.

10. The method of claim 1, wherein the base station comprises a neighbor base station.

11. The method of claim 10, wherein obtaining the CER elements comprises utilizing absolute square values of taps of a narrowband filtered channel impulse response (CIR).

12. The method of claim 11, wherein:

a noise variance estimate is calculated for each neighbor CER for each combination of transmit and receive antenna used to yield a threshold; and

neighbor CER elements above the threshold are selected.

13. The method of claim 12, further comprising:

averaging thresholded neighbor CER elements across a plurality of transmit antennas if present.

14. The method of claim 13, wherein:

the RSRP is calculated in a linear scale by accumulating averaged and thresholded CER elements, and further calculating the RSRP in units of dBm from the linear scale by converting to a logarithmic scale and applying appropriate normalizations.

15. The method of claim 14, wherein the RSRP is calculated by normalization based, at least in part, on a number of RS tones used for neighbor CER computation.

16. An apparatus for wireless communications, comprising:

means for obtaining a channel impulse response (CIR) from one or more reference signals (RSs) transmitted from one or more antennas of a base station;

means for calculating an absolute square per element of the CIR to generate channel energy response (CER) elements;

means for calculating a threshold value based on a noise variance estimated from a portion of the CER elements;

means for selecting CER elements that exceed the threshold value; and

means for computing a reference signal received power (RSRP) value based on the selected CER elements.

17. The apparatus of claim 16, wherein the base station comprises a serving base station.

18. The apparatus of claim 17, wherein the means for obtaining the CER elements is configured to utilize absolute square values of taps of a wideband coherently-filtered channel impulse response (CIR).

19. The apparatus of claim 17, wherein:

the RSs are received on a plurality of receive antennas; and

the means for obtaining the CER elements is configured to sum values across transmit antennas for different receive antennas.

20. The apparatus of claim 17, wherein the RSRP is calculated in a linear scale by accumulating selected CER elements, and further calculating RSRP in units of dBm from the linear scale by converting to a logarithmic scale and applying appropriate normalizations.

21. The apparatus of claim 20, wherein the RSRP is calculated by normalization based, at least in part, on a number of RS tones.

22. The apparatus of claim 21, wherein the RSRP is calculated by normalization based, at least in part, on a number of transmit antennas and the number of RS tones.

23. The apparatus of claim 16, further comprising:

means for computing a reference signal receive quality (RSRQ) value based on the computed RSRP.

24. The apparatus of claim 23, wherein the RSRQ value is computed based, at least in part, on at least one of:

a number of resource blocks (RBs) in a downlink if the base station comprises a serving base station, and a number of RBs used for neighbor measurements if the base station comprises a neighbor base station.

25. The apparatus of claim 16, wherein the base station comprises a neighbor base station.

26. The apparatus of claim 25, wherein the means for obtaining the CER elements is configured to utilize absolute square values of taps of a narrowband filtered channel impulse response (CIR).

27. The apparatus of claim 26, wherein:

a noise variance estimate is calculated for each neighbor CER for each combination of transmit and receive antenna used to yield a threshold; and

neighbor CER elements above the threshold are selected.

28. The apparatus of claim 27, further comprising:

means for averaging thresholded neighbor CER elements across a plurality of transmit antennas if present.

29. The apparatus of claim 28, wherein:

the RSRP is calculated in a linear scale by accumulating averaged and thresholded CER elements, and further calculating the RSRP in units of dBm from the linear scale by converting to a logarithmic scale and applying appropriate normalizations.

30. The apparatus of claim 29, wherein the RSRP is calculated by normalization based, at least in part, on a number of RS tones used for neighbor CER computation.

31. An apparatus for wireless communications, comprising:

at least one processor configured to;

obtain a channel impulse response (CIR) from one or more reference signals (RSs) transmitted from one or more antennas of a base station;

calculate an absolute square per element of the CIR to generate channel energy response (CER) elements;

calculate a threshold value based on a noise variance estimated from a portion of the CER elements;

select CER elements that exceed the threshold value; and

compute a reference signal received power (RSRP) value based on the selected CER elements; and

a memory coupled to the at least one processor.

32. A computer program product comprising a computer-readable medium having instructions stored thereon, the instructions executable by one or more processors for:

obtaining a channel impulse response (CIR) from one or more reference signals (RSs) transmitted from one or more antennas of a base station;

calculating an absolute square per element of the CIR to generate channel energy response (CER) elements;

calculating a threshold value based on a noise variance estimated from a portion of the CER elements;

selecting CER elements that exceed the threshold value; and

computing a reference signal received power (RSRP) value based on the selected CER elements.