SPATIAL LISTEN BEFORE TALK

• US 20190021092A1
• Filed: 07/10/2018
• Published: 01/17/2019
• Est. Priority Date: 07/12/2017
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Fakoorian, Seyed Ali Akbar, Zhang, Xiaoxia, Yoo, Taesang, Fan, Zhifei
• Granted Patent: US 10,609,714 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 72/541 using the level of interference

Abstract

Methods, systems, and devices for wireless communication are described. A user equipment (UE) may transmit a precoded reference signal to prevent interference with an incoming signal from a base station. The UE may determine a precoder for the reference signal based at least in part on a whitening matrix. In some examples, the UE may determine the precoder based at least in part on the whitening matrix and an effective channel between the base station and the UE. The precoded reference signal may be used by devices in other wireless communications systems to avoid interfering with a signal being received by the UE. In some examples, the UE may alternatively or additionally transmit an indication of the number of additional layers of the link between the UE and the base station that may be nulled out for a second link.

Claims

1. A method for wireless communication, comprising:

determining, by a user equipment (UE), a noise covariance matrix;

selecting a subset of eigen directions based at least in part on the noise covariance matrix;

determining a precoder based at least in part on the subset of eigen directions; and

transmitting a reference signal precoded by the precoder.

2. The method of claim 1, wherein:

selecting the subset of eigen directions of the noise covariance matrix comprises;

selecting a set number of largest eigen directions of the noise covariance matrix.

3. The method of claim 1, wherein:

the reference signal comprises a sounding reference signal.

4. The method of claim 1, further comprising:

determining a whitening matrix based at least in part on the noise covariance matrix; and

selecting the subset of eigen directions from a set of non-zero eigen directions of the whitening.

5. The method of claim 1, further comprising:

performing a signal measurement at the UE; and

determining the covariance matrix based at least in part on the signal measurement.

6. A method for wireless communication, comprising:

receiving, from a serving base station, an indication of the channel between the serving base station and a user equipment (UE);

determining, by the UE, an effective channel between the serving base station and the UE based at least in part on the indication of the channel between the serving base station and the UE;

determining a precoder based at least in part on the effective channel the serving base station and the UE; and

transmitting a reference signal precoded by the precoder.

7. The method of claim 6, further comprising:

receiving the indication of the channel between the serving base station and the UE comprises receiving a second precoded reference signal from the serving base station.

8. The method of claim 7, further comprising:

determining the effective channel between the UE and the serving base station based at least in part on the second precoded reference signal.

9. The method of claim 7, further comprising:

transmitting a third precoded reference signal to the serving base station; and

receiving the second precoded reference signal in response to the third precoded reference signal.

10. The method of claim 9, further comprising:

determining a whitening matrix based at least in part on a noise covariance matrix; and

precoding the third precoded reference signal based at least in part on the whitening matrix.

11. The method of claim 6, further comprising:

determining the precoder based at least in part on maximal-ratio combining (MRC) filtering.

12. The method of claim 6, further comprising:

determining the precoder based at least in part on minimum mean square error (MMSE) filtering.

13. The method of claim 6, further comprising:

determining a serving base station precoder based at least in part on the indication of the channel between the serving base station and the UE; and

determining the precoder based at least in part on the serving base station precoder.

14. The method of claim 13, further comprising:

determining a whitening matrix based at least in part on a noise covariance matrix; and

determining the precoder based at least in part on the whitening matrix.

15. A method for wireless communication, comprising:

receiving, at a wireless device in a first wireless communications system, scheduling information for a data transmission intended for the wireless device; and

transmitting a response to the scheduling information, wherein at least one of the scheduling information and the response to the scheduling information comprises an indication of a number of layers that can be nulled out for communications in a second wireless communications system.

16. The method of claim 15, further comprising:

measuring a downlink channel from a user equipment (UE) in the second wireless communications system; and

determining precoding weights based at least in part on the measuring.

17. An apparatus for wireless communication, comprising:

a processor;

memory in electronic communication with the processor; and

instructions stored in the memory and operable, when executed by the processor, to cause the apparatus to;

receive, from a serving base station, an indication of the channel between the serving base station and a user equipment (UE);

determine, by the UE, an effective channel between the serving base station and the UE based at least in part on the indication of the channel between the serving base station and the UE;

determine a precoder based at least in part on the effective channel the serving base station and the UE; and

transmit a reference signal precoded by the precoder.

18. The apparatus of claim 17, wherein the instructions are further executable by the processor to:

receive the indication of the channel between the serving base station and the UE comprises receiving a second precoded reference signal from the serving base station.

19. The apparatus of claim 18, wherein the instructions are further executable by the processor to:

determine the effective channel between the UE and the serving base station based at least in part on the second precoded reference signal.

20. The apparatus of claim 18, wherein the instructions are further executable by the processor to:

transmit a third precoded reference signal to the serving base station; and

receive the second precoded reference signal in response to the third precoded reference signal.

21. The apparatus of claim 20, wherein the instructions are further executable by the processor to:

determine a whitening matrix based at least in part on a noise covariance matrix; and

precode the third precoded reference signal based at least in part on the whitening matrix.

22. The apparatus of claim 17, wherein the instructions are further executable by the processor to:

determine the precoder based at least in part on maximal-ratio combining (MRC) filtering.

23. The apparatus of claim 17, wherein the instructions are further executable by the processor to:

determine the precoder based at least in part on minimum mean square error (MMSE) filtering.

24. The apparatus of claim 17, wherein the instructions are further executable by the processor to:

determine a serving base station precoder based at least in part on the indication of the channel between the serving base station and the UE; and

determine the precoder based at least in part on the serving base station precoder.

25. The apparatus of claim 24, wherein the instructions are further executable by the processor to:

determine a whitening matrix based at least in part on a noise covariance matrix; and

determine the precoder based at least in part on the whitening matrix.