Reverse link interference cancellation

• US 20070040704A1
• Filed: 01/18/2006
• Published: 02/22/2007
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Hou, Jilei, Padovani, Roberto, Black, Peter, Smee, John, Easton, Kenneth
• Granted Patent: US 9,071,344 B2
• Time in Patent Office: Days
• US Class Current: 340/981
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04W 52/12 Outer and inner loops

Abstract

A method and system for reverse link interference cancellation. One method comprises demodulating and decoding at least one signal sent from at least one access terminal and received by a first base station, sending demodulated, decoded information of the signal to a second base station, reconstructing the signal at the second base station, and subtracting the reconstructed signal from a buffer at the second base station.

Claims

1. A method to reduce interference, the method comprising:

demodulating and decoding at least one signal sent from at least one access terminal and received by a first base station;

sending demodulated, decoded information of the signal to a second base station;

reconstructing the signal at the second base station; and

subtracting the reconstructed signal from a buffer at the second base station.

2. The method of claim 1, further comprising receiving at least a portion of the signal from the access terminal at the second base station.

3. The method of claim 1, wherein the second base station is within a communication range of the access terminal.

4. The method of claim 1, wherein the signal comprises at least one of a pilot, an overhead channel and a traffic channel.

5. The method of claim 1, wherein the demodulated, decoded information comprises at least one of decoded data bits, re-encoded data bits, modulated symbols, and modulated/interleaved symbols.

6. The method of claim 1, further comprising using the demodulated, decoded information to estimate channel parameters at the second base station.

7. The method of claim 6, wherein the channel parameters comprise at least one of multipath delays and channel coefficients.

8. The method of claim 6, wherein the channel parameters comprise at least one of amplitude and phase of an orthogonal frequency division multiplexing (OFDM) tone.

9. The method of claim 1, wherein reconstructing the signal at the second base station comprises coding, modulation and filtering.

10. The method of claim 1, wherein reconstructing the signal at the second base station comprises coding, modulation and a Fourier transform.

11. The method of claim 1, wherein sending the demodulated information from the signal to a second base station uses a direct link between the first and second base stations.

12. The method of claim 1, wherein sending the demodulated information from the signal to a second base station uses a base station controller in communication with the first and second base stations.

13. The method of claim 1, wherein the signal comprises an interlace of time-separated subpackets corresponding to a packet.

14. The method of claim 13, further comprising:

attempting to decode the packet corresponding to one or more subpackets;

sending an acknowledgement signal for a successfully decoded packet; and

sending a negative acknowledgement signal for a non-successfully decoded packet.

15. The method of claim 13, wherein sending demodulated, decoded information of the signal to the second base station occurs between receiving two subpackets of a same interlace.

16. The method of claim 13, wherein demodulating and decoding the signal comprises demodulating the subpackets and attempting to decode packets from subpackets sent from a plurality of access terminals and received by the first base station in a same time frame.

17. The method of claim 1, wherein the signal is a code division multiple access signal.

18. The method of claim 1, wherein the signal is an orthogonal frequency division multiplexing signal.

19. A base station comprising:

a receiver configured to demodulate and decode at least one signal sent from at least one access terminal; and

a transmitter configured to send demodulated, decoded information of the signal directly to a second base station.

20. A system comprising:

a first base station comprising;

a receiver configured to demodulate and decode at least one signal sent from at least one access terminal; and

a transmitter configured to send demodulated, decoded information of the signal to a second base station; and

the second base station comprising;

a signal reconstruction unit configured to reconstruct the signal at the second base station; and

a subtractor configured to subtract the reconstructed signal from a buffer at the second base station.

21. The system of claim 20, wherein the second base station further comprises a receiver to receive at least a portion of the signal from the access terminal.

22. The system of claim 20, wherein the second base station is within a communication range of the access terminal.

23. The system of claim 20, wherein the signal comprises at least one of a pilot, an overhead channel and a traffic channel.

24. The system of claim 20, wherein the demodulated, decoded information comprises at least one of decoded data bits, re-encoded data bits, modulated symbols, and modulated/interleaved symbols.

25. The system of claim 20, wherein the second base station is configured to use the demodulated, decoded information to estimate channel parameters.

26. The system of claim 25, wherein the channel parameters comprise at least one of multipath delays and channel coefficients.

27. The system of claim 25, wherein the channel parameters comprise at least one of amplitude and phase of an orthogonal frequency division multiplexing (OFDM) tone.

28. The system of claim 20, wherein reconstructing the signal at the second base station comprises coding, modulation and filtering.

29. The system of claim 20, wherein reconstructing the signal at the second base station comprises coding, modulation and a Fourier transform.

30. The system of claim 20, wherein sending the demodulated information from the signal to a second base station uses a direct link between the first and second base stations.

31. The system of claim 20, wherein sending the demodulated information from the signal to a second base station uses a base station controller in communication with the first and second base stations.

32. The system of claim 20, wherein the signal comprises an interlace of time-separated subpackets corresponding to a packet.

33. The system of claim 32, wherein the first base station is configured to:

attempt to decode the packet corresponding to one or more subpackets;

send an acknowledgement signal for a successfully decoded packet; and

send a negative acknowledgement signal for a non-successfully decoded packet.

34. The system of claim 32, wherein the transmitter is configured to send demodulated, decoded information of the signal to the second base station between receiving two subpackets of a same interlace.

35. The system of claim 32, wherein the receiver is configured to demodulate the subpackets and attempt to decode packets from subpackets sent from a plurality of access terminals and received by the first base station in a same time frame.

36. The system of claim 20, wherein the signal is a code division multiple access signal.

37. The system of claim 20, wherein the signal is an orthogonal frequency division multiplexing signal.

38. A method to reduce interference, the method comprising:

at a first processing unit of a base station, demodulating and decoding a signal sent from an access terminal;

sending demodulated, decoded information of the signal to a second processing unit of the base station;

reconstructing the signal at the second processing unit; and

subtracting the reconstructed signal from a buffer of the second processing unit.

39. A base station comprising:

a first processing unit configured to;

demodulate and decode a signal sent from an access terminal; and

a second processing unit configured to;

receive demodulated, decoded information of the signal from the first processing unit;

reconstruct the signal at the second processing unit; and

subtract the reconstructed signal from a buffer of the second processing unit.

40. The base station of claim 39, wherein the processing units comprise channel cards.

41. A system comprising:

a plurality of stationary units configured to receive signals from at least one access terminal and transmit the signals to a central processor; and

the central processor comprising a buffer configured to store samples of the signals from the plurality of units, the central processor being configured to demodulate and decode samples from the buffer, reconstruct the demodulated, decoded samples, and subtract the reconstructed samples from samples stored in the buffer.

42. The system of claim 41, wherein the stationary units are spatially distributed over a geographical area such that each unit receives signals from a cell that is substantially distinct from other cells of other units.

43. The system of claim 41, wherein the signals transmitted by the units to the central processor are modulated, coded signals.

44. The system of claim 41, further comprising one or more optical fibers coupled to the plurality of units and the central processor.

45. The system of claim 41, wherein each unit comprises an antenna, an amplifier, a filter and a sampler.

46. The system of claim 41, wherein the buffer comprises a plurality of sub-buffers, each sub-buffer being configured to store samples of signals from a specific unit.

47. The system of claim 41, wherein the central processor is configured to combine multipath signals from two or more units.

48. The system of claim 41, wherein the central processor is configured to subtract the reconstructed samples from samples received by a unit that did not receive signals above a power threshold from the access terminal.

49. The system of claim 41, wherein the central processor is configured perform channel estimation for a unit that did not receive signals above a power threshold from the access terminal.

50. The system of claim 41, wherein the signals comprise at least one of a pilot, an overhead channel and a traffic channel.

51. The system of claim 41, wherein reconstructing the signals at the central processor comprises coding, modulation and filtering.

52. The system of claim 41, wherein reconstructing the signal at the central processor comprises coding, modulation and a Fourier transform.

53. The system of claim 41, wherein the signals comprises an interlace of time-separated subpackets corresponding to a packet.

54. The system of claim 41, wherein the central processor is configured to:

attempt to decode the packet corresponding to one or more subpackets;

send an acknowledgement signal for a successfully decoded packet; and

send a negative acknowledgement signal for a non-successfully decoded packet.

55. The system of claim 41, wherein demodulating and decoding the samples comprises demodulating the subpackets and attempting to decode packets from subpackets sent from the at least one access terminal.

56. The system of claim 41, wherein the signals are code division multiple access signals.

57. The system of claim 41, wherein the signals are an orthogonal frequency division multiplexing signals.

58. A method to reduce interference, the method comprising:

at a plurality of stationary receiving units, receiving signals transmitted by at least one access terminal and transferring the received signals to a central processor;

at the central processor, storing samples of the received signals;

at the central processor, demodulating and decoding the samples;

at the central processor, reconstructing the demodulated, decoded samples; and

at the central processor, subtracting the reconstructed samples from the stored samples.

59. The method of claim 58, wherein the signals transferred by the units to the central processor are modulated, coded signals.

60. The method of claim 58, further comprising combining multipath signals from two or more units.

61. The method of claim 58, further comprising subtracting the reconstructed samples from samples received by a unit that did not receive signals above a power threshold from the access terminal.

62. The method of claim 58, further comprising performing channel estimation for a unit that did not receive signals above a power threshold from the access terminal.

63. The method of claim 58, wherein the signals comprise at least one of a pilot, an overhead channel and a traffic channel.

64. The method of claim 58, wherein reconstructing the signals at the central processor comprises coding, modulation and filtering.

65. The method of claim 58, wherein reconstructing the signal at the central processor comprises coding, modulation and a Fourier transform.

66. The method of claim 58, wherein the signals comprises an interlace of time-separated subpackets corresponding to a packet.

67. The method of claim 58, further comprising:

at the central processor, attempting to decode the packet corresponding to one or more subpackets;

sending an acknowledgement signal for a successfully decoded packet; and

sending a negative acknowledgement signal for a non-successfully decoded packet.

68. The method of claim 58, wherein demodulating and decoding the samples comprises demodulating the subpackets and attempting to decode packets from subpackets sent from the at least one access terminal.

69. The method of claim 58, wherein the signals are code division multiple access signals.

70. The method of claim 58, wherein the signals are an orthogonal frequency division multiplexing signals.