REFERENCE SIGNAL DETECTION

• US 20140334434A1
• Filed: 08/01/2014
• Published: 11/13/2014
• Est. Priority Date: 11/07/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: BHATTAD, Kapil, HUANG, Yi, LUO, Tao, YOO, Taesang
• Granted Patent: US 9,742,515 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04J 11/005 of intercell interference

Abstract

Aspects of the disclosure are related to identifying whether an apparatus (e.g., base station, access point, etc.) is transmitting using a CRS based transmission scheme or a UE-RS based transmission scheme. Such detection may be necessary for PDSCH interference cancellation (IC) of a neighboring cell since a UE may not know which transmission scheme is used by the neighboring cell. For instance, the UE may know the transmission scheme of the serving cell, but the UE may not know the transmission scheme of a neighboring non-serving cell. As such, aspects of the disclosure provide for a blind detection algorithm to identify or determine a transmission mode or transmission scheme of a neighboring cell to then apply interference cancellation (IC) to an interfering signal received from the neighboring cell.

Claims

1. A method for signal processing in wireless communications, comprising:

receiving a signal, the signal including at least a first cell signal from a first cell;

calculating a power metric of the received signal;

determining a transmission scheme associated with the received signal, the transmission scheme determined to include a common reference signal (CRS) based transmission scheme or a user equipment reference signal (UE-RS) based transmission scheme based, at least in part, on the power metric; and

processing the received signal based, at least in part, on the determined transmission scheme.

2. The method of claim 1, wherein the processing the received signal comprises canceling interference from the received signal due to a second cell signal from a second cell based, at least in part, on the determined transmission scheme.

3. The method of claim 1, wherein the determining the transmission scheme comprises:

determining that the transmission scheme includes the UE-RS based transmission scheme if the power metric is greater than a threshold; and

determining that the transmission scheme includes the CRS based transmission scheme if the power metric is less than or equal to the threshold.

4. The method of claim 1, further comprising calculating a signal-to-noise ratio (SNR) metric using the calculated power metric,

wherein the determining the transmission scheme comprises:

determining that the transmission scheme includes the UE-RS based transmission scheme if the SNR metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the SNR metric is less than or equal to the threshold.

5. The method of claim 1, further comprising detecting a rank associated with the received signal by at least measuring a covariance on a data portion of the received signal, wherein the power metric is calculated using the rank,

wherein the determining the transmission scheme comprises:

determining that the transmission scheme includes the UE-RS based transmission scheme if the power metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the power metric is less than or equal to the threshold.

6. The method of claim 1, further comprising:

detecting a rank associated with the received signal by at least measuring a covariance on a data portion of the received signal, wherein the power metric is calculated using the rank; and

calculating a signal-to-noise ratio (SNR) metric using the calculated power metric,

wherein the determining the transmission scheme comprises;

determining that the transmission scheme includes the UE-RS based transmission scheme if the SNR metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the SNR metric is less than or equal to the threshold.

7. A method for signal processing in wireless communications, comprising:

receiving a signal, the signal including at least a first cell signal from a first cell;

deciding whether to use a rank associated with the received signal to determine a transmission scheme associated with the received signal;

determining the transmission scheme; and

processing the received signal based, at least in part, on the determined transmission scheme,

wherein when the rank is used to determine the transmission scheme, the method further comprises;

detecting one or more ranks associated with the received signal; and

determining a number of common reference signal (CRS) ports,

wherein the transmission scheme is determined to include a CRS based transmission scheme or a user equipment reference signal (UE-RS) based transmission scheme based, at least in part, on the one or more ranks associated with the received signal and the number of CRS ports.

8. The method of claim 7, wherein the processing the received signal comprises canceling interference from the received signal due to a second cell signal from a second cell based, at least in part, on the determined transmission scheme.

9. The method of claim 7,

wherein the one or more ranks associated with the received signal comprises a rank observed on data tones of the received signal and a rank observed on UE-RS tones of the received signal, and

wherein the determining the transmission scheme comprises:

determining that the transmission scheme includes the UE-RS based transmission scheme if the rank observed on the data tones is larger than the number of the CRS ports,

determining that the transmission scheme includes the UE-RS based transmission scheme if the rank observed on the data tones does not exceed the number of the CRS ports, and no CRS precoding leads to an observed covariance matrix on the data tones, and

determining that the transmission scheme includes the CRS based transmission scheme if the rank observed on the data tones is larger than 2 and the rank observed on the UE-RS tones is not equal to the rank observed on the data tones.

10. The method of claim 7, wherein when the rank is not used to determine the transmission scheme, the method further comprises detecting at least one of:

whether the signal is received in a multimedia broadcast over a single frequency network (MBSFN) subframe,

a transmit diversity scheme of the received signal,

a modulation order on UE-RS tones of the received signal,

a data symbol power on UE-RS tones of the received signal,

data tones of the received signal, or

a physical downlink control channel (PDCCH) of the second cell.

11. The method of claim 10, wherein when the signal is detected as being received in the MBSFN subframe, the determining the transmission scheme includes identifying the transmission scheme as the UE-RS based transmission scheme.

12. The method of claim 10, wherein when the transmit diversity scheme of the received signal is detected, the method further comprises detecting a rate-matching pattern of the received signal;

and

the determining the transmission scheme includes identifying that the transmission scheme is the UE-RS based transmission scheme based on an appearance of the transmit diversity scheme and the rate-matching pattern.

13. The method of claim 10, wherein when the modulation order on UE-RS tones of the received signal is detected, the determining the transmission scheme includes identifying that the transmission scheme is the CRS based transmission scheme if the modulation order is not quadrature phase shift keying (QPSK).

14. The method of claim 10, wherein when the data symbol power on UE-RS tones of the received signal is detected, the determining the transmission scheme includes identifying that the transmission scheme is the CRS based transmission scheme if the data symbol power varies across the UE-RS tones.

15. The method of claim 10, wherein when the data tones of the received signal are detected, the method further comprises estimating covariance on the data tones of the received signal;

and

the determining the transmission scheme includes identifying that the transmission scheme is the UE-RS based transmission scheme if the estimated covariance does not correspond to at least one of a CRS based channel codebook, a CRS based channel and transmit diversity scheme, or a CRS based channel and cyclic delay diversity scheme.

16. The method of claim 10, wherein when the PDCCH of the second cell is detected, the method further comprises decoding the PDCCH of the second cell;

and

the determining the transmission scheme includes identifying the transmission scheme based on the decoded PDCCH of the second cell.

17. An apparatus for signal processing in wireless communications, comprising:

a memory; and

at least one processor configured to;

receive a signal, the signal including at least a first cell signal from a first cell,

calculate a power metric of the received signal,

determine a transmission scheme associated with the received signal, the transmission scheme determined to include a common reference signal (CRS) based transmission scheme or a user equipment reference signal (UE-RS) based transmission scheme based, at least in part, on the power metric, and

process the received signal based, at least in part, on the determined transmission scheme.

18. The apparatus of claim 17, wherein the at least one processor is configured to determine the transmission scheme by:

determining that the transmission scheme includes the UE-RS based transmission scheme if the power metric is greater than a threshold; and

determining that the transmission scheme includes the CRS based transmission scheme if the power metric is less than or equal to the threshold.

19. The apparatus of claim 17, wherein the at least one processor is further configured to calculate a signal-to-noise ratio (SNR) metric using the calculated power metric,

wherein the at least one processor is configured to determine the transmission scheme by:

determining that the transmission scheme includes the UE-RS based transmission scheme if the SNR metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the SNR metric is less than or equal to the threshold.

20. The apparatus of claim 17, wherein the at least one processor is further configured to detect a rank associated with the received signal by at least measuring a covariance on a data portion of the received signal, wherein the power metric is calculated using the rank,

wherein the at least one processor is configured to determine the transmission scheme by:

determining that the transmission scheme includes the UE-RS based transmission scheme if the power metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the power metric is less than or equal to the threshold.

21. The apparatus of claim 17, wherein the at least one processor is further configured to:

detect a rank associated with the received signal by at least measuring a covariance on a data portion of the received signal, wherein the power metric is calculated using the rank; and

calculate a signal-to-noise ratio (SNR) metric using the calculated power metric,

wherein the at least one processor is configured to determine the transmission scheme by;

determining that the transmission scheme includes the UE-RS based transmission scheme if the SNR metric is greater than a threshold, and

determining that the transmission scheme includes the CRS based transmission scheme if the SNR metric is less than or equal to the threshold.

22. An apparatus for signal processing in wireless communications, comprising:

a memory; and

at least one processor configured to;

receive a signal, the signal including at least a first cell signal from a first cell,

decide whether to use a rank associated with the received signal to determine a transmission scheme associated with the received signal,

determine the transmission scheme, and

process the received signal based, at least in part, on the determined transmission scheme,

wherein when the rank is used to determine the transmission scheme, the at least one processor is further configured to;

detect one or more ranks associated with the received signal, and

determine a number of common reference signal (CRS) ports,

wherein the transmission scheme is determined to include a CRS based transmission scheme or a user equipment reference signal (UE-RS) based transmission scheme based, at least in part, on the one or more ranks associated with the received signal and the number of CRS ports.

23. The apparatus of claim 22,

wherein the one or more ranks associated with the received signal comprises a rank observed on data tones of the received signal and a rank observed on UE-RS tones of the received signal, and

wherein the at least one processor is configured to determine the transmission scheme by:

determining that the transmission scheme includes the UE-RS based transmission scheme if the rank observed on the data tones is larger than the number of the CRS ports,

determining that the transmission scheme includes the UE-RS based transmission scheme if the rank observed on the data tones does not exceed the number of the CRS ports, and no CRS precoding leads to an observed covariance matrix on the data tones, and

determining that the transmission scheme includes the CRS based transmission scheme if the rank observed on the data tones is larger than 2 and the rank observed on the UE-RS tones is not equal to the rank observed on the data tones.

24. The apparatus of claim 22, wherein when the rank is not used to determine the transmission scheme, the at least one processor is further configured to detect at least one of:

whether the signal is received in a multimedia broadcast over a single frequency network (MBSFN) subframe,

a transmit diversity scheme of the received signal,

a modulation order on UE-RS tones of the received signal,

a data symbol power on UE-RS tones of the received signal,

data tones of the received signal, or

a physical downlink control channel (PDCCH) of the second cell.

25. The apparatus of claim 24, wherein when the signal is detected as being received in the MBSFN subframe, the at least one processor is configured to determine the transmission scheme by identifying the transmission scheme as the UE-RS based transmission scheme.

26. The apparatus of claim 24, wherein when the transmit diversity scheme of the received signal is detected, the at least one processor is further configured to detect a rate-matching pattern of the received signal;

and

the at least one processor is configured to determine the transmission scheme by identifying that the transmission scheme is the UE-RS based transmission scheme based on an appearance of the transmit diversity scheme and the rate-matching pattern.

27. The apparatus of claim 24, wherein when the modulation order on UE-RS tones of the received signal is detected, the at least one processor is configured to determine the transmission scheme by identifying that the transmission scheme is the CRS based transmission scheme if the modulation order is not quadrature phase shift keying (QPSK).

28. The apparatus of claim 24, wherein when the data symbol power on UE-RS tones of the received signal is detected, the at least one processor is configured to determine the transmission scheme by identifying that the transmission scheme is the CRS based transmission scheme if the data symbol power varies across the UE-RS tones.

29. The apparatus of claim 24, wherein when the data tones of the received signal are detected, the at least one processor is further configured to estimate covariance on the data tones of the received signal;

and

the at least one processor is configured to determine the transmission scheme by identifying that the transmission scheme is the UE-RS based transmission scheme if the estimated covariance does not correspond to at least one of a CRS based channel codebook, a CRS based channel and transmit diversity scheme, or a CRS based channel and cyclic delay diversity scheme.

30. The apparatus of claim 24, wherein when the PDCCH of the second cell is detected, the at least one processor is further configured to decode the PDCCH of the second cell;

and

the at least one processor is configured to determine the transmission scheme by identifying the transmission scheme based on the decoded PDCCH of the second cell.