Interference cancellation in wireless communication

• US 20070121554A1
• Filed: 07/24/2006
• Published: 05/31/2007
• Est. Priority Date: 08/01/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Luo, Tao, Younis, Waleed, Sambhwani, Sharad, Malladi, Durga
• Granted Patent: US 8,493,942 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 25/0236 using estimation of the other symbols

Abstract

Techniques for recovering transmissions on data and control channels with interference cancellation are described. A receiver derives a first interference estimate for a first channel based on a first channel estimate and cancels the first interference estimate from an input signal. The receiver thereafter derives a second interference estimate for the first channel based on a second channel estimate and cancels the second interference estimate in place of the first interference estimate from the input signal. The receiver may derive the first channel estimate based on pilot symbols and may derive the second channel estimate based on a correctly decoded packet. The second channel estimate may be of higher quality than the first channel estimate.

Claims

1. An apparatus comprising:

at least one processor to derive a first interference estimate for a first channel based on a first channel estimate, to cancel the first interference estimate from an input signal, to derive a second interference estimate for the first channel based on a second channel estimate, and to cancel the second interference estimate in place of the first interference estimate from the input signal; and

a memory in communication with the at least one processor.

2. The apparatus of claim 1, wherein the at least one processor derives the first channel estimate based on pilot symbols and derives the second channel estimate based on data symbols.

3. The apparatus of claim 1, wherein the at least one processor derives the second channel estimate based on a correctly decoded packet from a second channel.

4. The apparatus of claim 3, wherein the at least one processor processes the input signal after canceling the first interference estimate to obtain the correctly decoded packet from the second channel.

5. The apparatus of claim 3, wherein the at least one processor derives a third interference estimate for the second channel based on the second channel estimate and the correctly decoded packet, and cancels the third interference estimate from the input signal.

6. The apparatus of claim 3, wherein the at least one processor derives the second channel estimate for multiple time intervals in which the correctly decoded packet is sent, and derives the second interference estimate for the multiple time intervals.

7. The apparatus of claim 3, wherein the at least one processor reconstructs data sent on the first channel in multiple time intervals in which the correctly decoded packet is sent, and derives the second interference estimate for the first channel based on the second channel estimate and the reconstructed data for the first channel.

8. The apparatus of claim 1, wherein the at least one processor derives and cancels the first and second interference estimates for a first terminal and processes the input signal after canceling the second interference estimate to recover signaling and data for a second terminal.

9. The apparatus of claim 3, wherein the first channel is a control channel and the second channel is a data channel.

10. The apparatus of claim 9, wherein the first channel carries signaling for the second channel.

11. The apparatus of claim 3, wherein the first channel is sent without hybrid automatic retransmission (HARQ) and the second channel is sent with HARQ.

12. The apparatus of claim 1, wherein the at least one processor derives the first channel estimate based on pilot symbols from a Dedicated Physical Control Channel (DPCCH), and derives the second channel estimate based on data symbols from an E-DCH Dedicated Physical Data Channel (E-DPDCH)

13. The apparatus of claim 12, wherein the first channel is the DPCCH or an E-DCH Dedicated Physical Control Channel (E-DPCCH).

14. A method comprising:

deriving a first interference estimate for a first channel based on a first channel estimate;

canceling the first interference estimate from an input signal;

deriving a second interference estimate for the first channel based on a second channel estimate; and

canceling the second interference estimate in place of the first interference estimate from the input signal.

15. The method of claim 14, further comprising:

deriving the first channel estimate based on pilot symbols; and

deriving the second channel estimate based on data symbols.

16. The method of claim 14, further comprising:

processing the input signal after canceling the first interference estimate to obtain a correctly decoded packet from the second channel; and

deriving the second channel estimate based on the correctly decoded packet.

17. The method of claim 16, further comprising:

deriving the second channel estimate for multiple time intervals in which the correctly decoded packet is sent, and wherein the second interference estimate is derived for the multiple time intervals.

18. The method of claim 14, wherein the first and second interference estimates are derived and canceled for a first terminal, the method further comprising:

processing the input signal after canceling the second interference estimate to recover signaling and data for a second terminal.

19. An apparatus comprising:

means for deriving a first interference estimate for a first channel based on a first channel estimate;

means for canceling the first interference estimate from an input signal;

means for deriving a second interference estimate for the first channel based on a second channel estimate; and

means for canceling the second interference estimate in place of the first interference estimate from the input signal.

20. The apparatus of claim 19, further comprising:

means for deriving the first channel estimate based on pilot symbols; and

means for deriving the second channel estimate based on data symbols.

21. The apparatus of claim 19, further comprising:

means for processing the input signal after canceling the first interference estimate to obtain a correctly decoded packet from the second channel; and

means for deriving the second channel estimate based on the correctly decoded packet.

22. The apparatus of claim 21, further comprising:

means for deriving the second channel estimate for multiple time intervals in which the correctly decoded packet is sent, and wherein the second interference estimate is derived for the multiple time intervals.

23. The apparatus of claim 19, wherein the first and second interference estimates are derived and canceled for a first terminal, the apparatus further comprising:

means for processing the input signal after canceling the second interference estimate to recover signaling and data for a second terminal.

24. An apparatus comprising:

at least one processor to derive a channel estimate based on a data channel, to derive at least one interference estimate for at least one control channel based on the channel estimate, and to cancel the at least one interference estimate from an input signal; and

a memory in communication with the at least one processor.

25. The apparatus of claim 24, wherein the at least one processor processes the input signal to obtain a correctly decoded packet for the data channel, and derives the channel estimate based on the correctly decoded packet.

26. The apparatus of claim 24, wherein the at least one processor receives multiple transmissions in multiple time intervals for the data channel, processes the multiple transmissions to obtain a correctly decoded packet, derives the channel estimate for the multiple time intervals based on the correctly decoded packet, and derives the at least one interference estimate for the multiple time intervals.

27. The apparatus of claim 24, wherein the at least one processor receives a retransmission for a correctly decoded packet and cancels interference due to the retransmission without decoding the retransmission.

28. The apparatus of claim 26, wherein the at least one control channel comprises a control channel associated with the data channel, and wherein the at least one processor recovers signaling sent on the control channel in a last time interval among the multiple time intervals, reconstructs signaling sent on the control channel in remaining ones of the multiple time intervals based on the recovered signaling for the last time interval, and derives an interference estimate for the control channel for the multiple time intervals based on the channel estimate, the recovered signaling for the last time interval, and the reconstructed signaling for the remaining time intervals.

29. The apparatus of claim 28, wherein the signaling sent on the control channel in each time interval comprises format information and redundancy version information for the data channel, the format information being unchanged for the multiple time intervals, and the redundancy version information changing in a deterministic manner across the multiple time intervals.

30. The apparatus of claim 24, wherein the at least one processor derives the channel estimate and the at least one interference estimate for a first terminal, and processes the input signal after canceling the at least one interference estimate for the first terminal to recover signaling and data for a second terminal.

31. A method comprising:

deriving a channel estimate based on a data channel;

deriving at least one interference estimate for at least one control channel based on the channel estimate; and

canceling the at least one interference estimate from an input signal.

32. The method of claim 31, wherein the deriving the channel estimate based on the data channel comprises

processing the input signal to obtain a correctly decoded packet for the data channel, and

deriving the channel estimate based on the correctly decoded packet.

33. The method of claim 31, wherein the deriving the channel estimate based on the data channel comprises

receiving multiple transmissions in multiple time intervals for the data channel,

processing the multiple transmissions to obtain a correctly decoded packet, and

deriving the channel estimate for the multiple time intervals based on the correctly decoded packet, and wherein the at least one interference estimate is derived for the multiple time intervals.

34. The method of claim 31, wherein the at least one interference estimate is derived and canceled for a first terminal, the method further comprising:

processing the input signal after canceling the at least one interference estimate for the first terminal to recover signaling and data for a second terminal.

35. An apparatus comprising:

means for deriving a channel estimate based on a data channel;

means for deriving at least one interference estimate for at least one control channel based on the channel estimate; and

means for canceling the at least one interference estimate from an input signal.

36. The apparatus of claim 35, wherein the means for deriving the channel estimate based on the data channel comprises

means for processing the input signal to obtain a correctly decoded packet for the data channel, and

means for deriving the channel estimate based on the correctly decoded packet.

37. The apparatus of claim 35, wherein the means for deriving the channel estimate based on the data channel comprises

means for receiving multiple transmissions in multiple time intervals for the data channel,

means for processing the multiple transmissions to obtain a correctly decoded packet, and

means for deriving the channel estimate for the multiple time intervals based on the correctly decoded packet, and wherein the at least one interference estimate is derived for the multiple time intervals.

38. The apparatus of claim 35, wherein the at least one interference estimate is derived and canceled for a first terminal, the apparatus further comprising:

means for processing the input signal after canceling the at least one interference estimate for the first terminal to recover signaling and data for a second terminal.