INTERFERENCE MITIGATION FOR DOWNLINK IN A WIRELESS COMMUNICATION SYSTEM

• US 20100309861A1
• Filed: 04/20/2010
• Published: 12/09/2010
• Est. Priority Date: 06/04/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Gorokhov, Alexei Y.
• Granted Patent: US 9,264,097 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects

Abstract

Techniques for mitigating interference in a wireless communication system are described. In an aspect, pertinent transmission parameters for a served UE may be sent to at least one interfered UE to support interference mitigation. In one design, information for at least one transmission parameter for a data transmission sent by a first cell to a first UE may be transmitted to at least one UE served by a second cell to enable the at least one UE to perform interference mitigation for the data transmission sent by the first cell to the first UE. The information may be transmitted by either the first cell or the second cell. In another aspect, a cell may send transmission parameters for a UE via a pilot. In yet another aspect, scrambling may be performed by a cell at symbol level to enable an interfered UE to distinguish between modulation symbols of desired and interfering transmissions.

Claims

1. A method for wireless communication, comprising:

obtaining at a first user equipment (UE) a received signal comprising a first data transmission sent by a first cell to the first UE and a second data transmission sent by a second cell to a second UE;

obtaining information for at least one transmission parameter for the second data transmission; and

performing interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

2. The method of claim 1, wherein the performing interference mitigation comprises performing interference mitigation for the second data transmission at symbol level, without decoding the second data transmission to recover any packet sent by the second cell to the second UE.

3. The method of claim 1, wherein the performing interference mitigation comprises performing interference mitigation for the second data transmission at packet level by decoding the second data transmission to recover at least one packet sent by the second cell to the second UE and estimating interference due to the second data transmission based on the at least one packet.

4. The method of claim 1, wherein the performing interference mitigation comprises

demodulating the received signal based on the information for the at least one transmission parameter to obtain demodulated symbols for the second data transmission,

estimating interference due to the second data transmission based on the demodulated symbols for the second data transmission,

subtracting the estimated interference from the received signal to obtain an interference-canceled signal, and

demodulating the interference-canceled signal to obtain demodulated symbols for the first data transmission.

5. The method of claim 1, wherein the performing interference mitigation comprises performing joint demodulation on the received signal based on the information for the at least one transmission parameter to obtain demodulated symbols for the first and second data transmissions.

6. The method of claim 1, wherein the performing interference mitigation comprises performing demodulation with interference mitigation and decoding for a plurality of iterations, wherein an output of demodulation in each iteration is used for decoding in the iteration, and wherein an output of decoding in each iteration except for a final iteration is used for demodulation in next iteration.

7. The method of claim 1, wherein the performing interference mitigation comprises performing demodulation with interference mitigation for a plurality of hypotheses, each hypothesis corresponding to a different set of one or more values for one or more of the at least one transmission parameter.

8. The method of claim 1, wherein the performing interference mitigation comprises

obtaining a channel estimate for a wireless channel from the second cell to the first UE based on information for one or more of the at least one transmission parameter, and

performing demodulation with interference mitigation based further on the channel estimate to obtain demodulated symbols for the first data transmission.

9. The method of claim 1, wherein the information for the at least one transmission parameter comprises a modulation order, or a modulation and coding scheme (MCS), or a traffic-to-pilot ratio (T2P), or precoding information, or a transmission rank, or assigned resources for the second data transmission, or a combination thereof.

10. The method of claim 1, wherein the obtaining the information for the at least one transmission parameter comprises obtaining actual value of the at least one transmission parameter used by the second cell for the second data transmission.

11. The method of claim 1, wherein the obtaining the information for the at least one transmission parameter comprises obtaining default value of the at least one transmission parameter likely to be used by the second cell for the second data transmission.

12. The method of claim 1, wherein the obtaining the information for the at least one transmission parameter comprises obtaining the information for the at least one transmission parameter from signaling transmitted by the first cell or the second cell.

13. The method of claim 1, wherein the obtaining the information for the at least one transmission parameter comprises obtaining the information for the at least one transmission parameter from a pilot transmitted by the second cell to the second UE.

14. An apparatus for wireless communication, comprising:

means for obtaining at a first user equipment (UE) a received signal comprising a first data transmission sent by a first cell to the first UE and a second data transmission sent by a second cell to a second UE;

means for obtaining information for at least one transmission parameter for the second data transmission; and

means for performing interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

15. The apparatus of claim 14, wherein the means for performing interference mitigation comprises means for performing interference mitigation for the second data transmission at symbol level, without decoding the second data transmission to recover any packet sent by the second cell to the second UE.

16. The apparatus of claim 14, wherein the means for performing interference mitigation comprises means for performing interference mitigation for the second data transmission at packet level by decoding the second data transmission to recover at least one packet sent by the second cell to the second UE and estimating interference due to the second data transmission based on the at least one packet.

17. The apparatus of claim 14, wherein the means for performing interference mitigation comprises

means for demodulating the received signal based on the information for the at least one transmission parameter to obtain demodulated symbols for the second data transmission,

means for estimating interference due to the second data transmission based on the demodulated symbols for the second data transmission,

means for subtracting the estimated interference from the received signal to obtain an interference-canceled signal, and

means for demodulating the interference-canceled signal to obtain demodulated symbols for the first data transmission.

18. The apparatus of claim 14, wherein the means for performing interference mitigation comprises means for performing joint demodulation on the received signal based on the information for the at least one transmission parameter to obtain demodulated symbols for the first and second data transmissions.

19. An apparatus for wireless communication, comprising:

at least one processor configured to obtain at a first user equipment (UE) a received signal comprising a first data transmission sent by a first cell to the first UE and a second data transmission sent by a second cell to a second UE, to obtain information for at least one transmission parameter for the second data transmission, and to perform interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

20. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to obtain at a first user equipment (UE) a received signal comprising a first data transmission sent by a first cell to the first UE and a second data transmission sent by a second cell to a second UE,

code for causing the at least one computer to obtain information for at least one transmission parameter for the second data transmission, and

code for causing the at least one computer to perform interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

21. A method for wireless communication, comprising:

obtaining information for at least one transmission parameter for a data transmission sent by a first cell to a user equipment (UE); and

transmitting the information for the at least one transmission parameter to at least one UE served by a second cell to enable the at least one UE to perform interference mitigation for the data transmission sent by the first cell to the UE.

22. The method of claim 21, wherein the information for the at least one transmission parameter comprises a modulation order, or a modulation and coding scheme (MCS), or a traffic-to-pilot ratio (T2P), or precoding information, or a transmission rank, or assigned resources for the data transmission, or a combination thereof.

23. The method of claim 21, wherein the obtaining the information and the transmitting the information are performed by the first cell.

24. The method of claim 21, wherein the obtaining the information and the transmitting the information are performed by the second cell, and wherein the obtaining the information comprises receiving the information for the at least one transmission parameter from the first cell by the second cell via backhaul.

25. The method of claim 21, further comprising:

identifying the UE or the first cell as potential interferer to the at least one UE based on pilot measurement from the UE, or location of the UE, or pilot measurements from the at least one UE, or location of the at least one UE, or a combination thereof.

26. An apparatus for wireless communication, comprising:

means for obtaining information for at least one transmission parameter for a data transmission sent by a first cell to a user equipment (UE); and

means for transmitting the information for the at least one transmission parameter to at least one UE served by a second cell to enable the at least one UE to perform interference mitigation for the data transmission sent by the first cell to the UE.

27. The apparatus of claim 26, wherein the information for the at least one transmission parameter comprises a modulation order, or a modulation and coding scheme (MCS), or a traffic-to-pilot ratio (T2P), or precoding information, or a transmission rank, or assigned resources for the data transmission, or a combination thereof.

28. An apparatus for wireless communication, comprising:

at least one processor configured to obtain information for at least one transmission parameter for a data transmission sent by a first cell to a user equipment (UE), and to transmit the information for the at least one transmission parameter to at least one UE served by a second cell to enable the at least one UE to perform interference mitigation for the data transmission sent by the first cell to the UE.

29. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to obtain information for at least one transmission parameter for a data transmission sent by a first cell to a user equipment (UE), and

code for causing the at least one computer to transmit the information for the at least one transmission parameter to at least one UE served by a second cell to enable the at least one UE to perform interference mitigation for the data transmission sent by the first cell to the UE.

30. A method for wireless communication, comprising:

generating a data transmission based on at least one transmission parameter;

generating a pilot comprising information for the at least one transmission parameter; and

transmitting the pilot and the data transmission.

31. The method of claim 30, wherein the information for the at least one transmission parameter comprises a modulation order, or a modulation and coding scheme (MCS), or a traffic-to-pilot ratio (T2P), or precoding information, or a transmission rank, or assigned resources for the data transmission, or a combination thereof.

32. The method of claim 30, wherein the generating the pilot comprises

generating a pseudo-random number (PN) sequence based on the information for the at least one transmission parameter, and

generating modulation symbols for the pilot based on the PN sequence.

33. An apparatus for wireless communication, comprising:

means for generating a data transmission based on at least one transmission parameter;

means for generating a pilot comprising information for the at least one transmission parameter; and

means for transmitting the pilot and the data transmission.

34. The apparatus of claim 33, wherein the means for generating the pilot comprises

means for generating a pseudo-random number (PN) sequence based on the information for the at least one transmission parameter, and

means for generating modulation symbols for the pilot based on the PN sequence.

35. An apparatus for wireless communication, comprising:

at least one processor configured to generate a data transmission based on at least one transmission parameter, to generate a pilot comprising information for the at least one transmission parameter, and to transmit the pilot and the data transmission.

36. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to generate a data transmission based on at least one transmission parameter,

code for causing the at least one computer to generate a pilot comprising information for the at least one transmission parameter, and

code for causing the at least one computer to transmit the pilot and the data transmission.

37. A method for wireless communication, comprising:

generating modulation symbols for a data transmission;

scrambling the modulation symbols based on a scrambling sequence to obtain scrambled symbols; and

transmitting the scrambled symbols for the data transmission.

38. The method of claim 37, further comprising:

generating the scrambling sequence based on a cell identity (ID), or a user equipment identity (UE ID), or both.

39. The method of claim 37, further comprising:

generating the scrambling sequence based on a modulation order not used for the data transmission.

40. The method of claim 37, further comprising:

generating the scrambling sequence based on a modulation order that does not map the scrambled symbols of the data transmission from a cell to valid scrambled symbols from another cell.

41. The method of claim 37, further comprising:

generating the scrambling sequence based on 8-ary phase shift keying (8-PSK).

42. An apparatus for wireless communication, comprising:

means for generating modulation symbols for a data transmission;

means for scrambling the modulation symbols based on a scrambling sequence to obtain scrambled symbols; and

means for transmitting the scrambled symbols for the data transmission.

43. The apparatus of claim 42, further comprising:

means for generating the scrambling sequence based on a cell identity (ID), or a user equipment identity (UE ID), or both.

44. The apparatus of claim 42, further comprising:

means for generating the scrambling sequence based on a modulation order not used for the data transmission.

45. An apparatus for wireless communication, comprising:

at least one processor configured to generate modulation symbols for a data transmission, to scramble the modulation symbols based on a scrambling sequence to obtain scrambled symbols, and to transmit the scrambled symbols for the data transmission.

46. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to generate modulation symbols for a data transmission,

code for causing the at least one computer to scramble the modulation symbols based on a scrambling sequence to obtain scrambled symbols, and

code for causing the at least one computer to transmit the scrambled symbols for the data transmission.

47. A method for wireless communication, comprising:

descrambling received symbols based on a scrambling sequence to obtain descrambled symbols; and

demodulating the descrambled symbols to obtain demodulated symbols.

48. The method of claim 47, further comprising:

generating the scrambling sequence based on a cell identity (ID), or a user equipment identity (UE ID), or both.

49. The method of claim 47, further comprising:

obtaining the received symbols comprising a first data transmission sent by a first cell to a first user equipment (UE) and a second data transmission sent by a second cell to a second UE; and

obtaining information for at least one transmission parameter for the second data transmission, and wherein the demodulating the descrambled symbols comprises

demodulating the descrambled symbols with interference mitigation based on the information for the at least one transmission parameter to recover the first data transmission sent to the first UE.

50. An apparatus for wireless communication, comprising:

means for descrambling received symbols based on a scrambling sequence to obtain descrambled symbols; and

means for demodulating the descrambled symbols to obtain demodulated symbols.

51. The apparatus of claim 50, further comprising:

means for generating the scrambling sequence based on a cell identity (ID), or a user equipment identity (UE ID), or both.

52. The apparatus of claim 50, further comprising:

means for obtaining the received symbols comprising a first data transmission sent by a first cell to a first user equipment (UE) and a second data transmission sent by a second cell to a second UE; and

means for obtaining information for at least one transmission parameter for the second data transmission, and wherein the means for demodulating the descrambled symbols comprises

means for demodulating the descrambled symbols with interference mitigation based on the information for the at least one transmission parameter to recover the first data transmission sent to the first UE.

53. An apparatus for wireless communication, comprising:

at least one processor configured to descramble received symbols based on a scrambling sequence to obtain descrambled symbols, and to demodulate the descrambled symbols to obtain demodulated symbols.

54. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to descramble received symbols based on a scrambling sequence to obtain descrambled symbols, and

code for causing the at least one computer to demodulate the descrambled symbols to obtain demodulated symbols.

55. A method for wireless communication, comprising:

receiving at a first user equipment (UE) a multi-user multiple-input multiple-output (MU-MIMO) transmission comprising a first data transmission sent by a cell to the first UE and a second data transmission sent by the cell to a second UE;

obtaining information for at least one transmission parameter for the second data transmission; and

performing interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

56. The method of claim 55, wherein the performing interference mitigation comprises performing interference mitigation for the second data transmission at symbol level, without decoding the second data transmission to recover any packet sent by the cell to the second UE.

57. An apparatus for wireless communication, comprising:

means for receiving at a first user equipment (UE) a multi-user multiple-input multiple-output (MU-MIMO) transmission comprising a first data transmission sent by a cell to the first UE and a second data transmission sent by the cell to a second UE;

means for obtaining information for at least one transmission parameter for the second data transmission; and

means for performing interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

58. The apparatus of claim 57, wherein the means for performing interference mitigation comprises means for performing interference mitigation for the second data transmission at symbol level, without decoding the second data transmission to recover any packet sent by the cell to the second UE.

59. An apparatus for wireless communication, comprising:

at least one processor configured to receive at a first user equipment (UE) a multi-user multiple-input multiple-output (MU-MIMO) transmission comprising a first data transmission sent by a cell to the first UE and a second data transmission sent by the cell to a second UE, to obtain information for at least one transmission parameter for the second data transmission, and to perform interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.

60. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to receive at a first user equipment (UE) a multi-user multiple-input multiple-output (MU-MIMO) transmission comprising a first data transmission sent by a cell to the first UE and a second data transmission sent by the cell to a second UE,

code for causing the at least one computer to obtain information for at least one transmission parameter for the second data transmission, and

code for causing the at least one computer to perform interference mitigation for the second data transmission, based on the information for the at least one transmission parameter, to recover the first data transmission sent to the first UE.