Co-channel interference canceller

• US 6,842,476 B2
• Filed: 02/09/2001
• Issued: 01/11/2005
• Est. Priority Date: 02/09/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lindoff, Bengt, Stenström, Niklas
• Primary Examiner(s): Ha, Dac V.
• Application Number:
  US09/779,553
• Publication Number:
  US 20020159547A1
• Time in Patent Office: 1,432 Days
• Field of Search: 375/144, 375/148, 375/346, 370/319, 370/442, 370/465, 370/466, 455/63, 455/222, 455/226.1, 455/226.3, 455/278.1, 455/283, 455/276, 455/307
• US Class Current: 375/144
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 25/03331 Arrangements for the joint estimation of multiple sequences

Abstract

A method and apparatus for processing a received signal containing a desired burst and a co-channel interferer burst are disclosed. The invention includes receiving the received signal from a front end receiver. A time offset between the desired burst and the co-channel interferer burst is detected. A detection procedure is then selected based on the time offset between the desired burst and the co-channel interferer burst. Preferably, one of three detection procedures is selected based on the time offset detected and optionally the signal strength of the co-channel interferer burst. If a first or second time offset is detected, then a joint detection or an iterative detection procedure is selected and performed, respectively. Finally, if a third time offset is detected or if the co-channel interferer has a low signal strength, then a conventional detection procedure is selected and performed.

Claims

1. A method of processing a received signal containing a desired burst and a desired burst and co-channel interferer burst, the method comprising:

receiving the received signal from a front end receiver;

detecting a time offset between the desired burst and the co-channel interferer burst; and

selecting a detection procedure based on the time offset between the desired burst and the co-channel interferer burst.

2. The method of claim 1 further comprising:

selecting a joint detection procedure when a training sequence of the desired burst and a training sequence of the co-channel interferer burst overlap by at least a first predetermined amount;

if the training sequence of the desired burst and the training sequence of the co-channel interferer do not overlap each other by at least the first predetermined amount, then selecting an iterative detection procedure when the training sequence of the co-channel interferer burst overlaps the desired burst by a second predetermined amount; and

selecting a conventional detection procedure when the training sequence of the co-channel interferer burst does not overlap the desired burst by at least the second predetermined amount.

3. The method of claim 2, wherein the first predetermined amount is about 50%.

4. The method of claim 2, wherein the second predetermined amount is about 50%.

5. The method of claim 2, wherein the joint detection procedure comprises:

finding a synchronization position by correlating the training sequences of the desired burst and the co-channel interferer burst with the received burst;

estimating a first channel and a second channel jointly, thereby generating a first channel estimate and a second channel estimate; and

providing the received signal, the first channel estimate, the second channel estimate and the synchronization position to an equalizer, wherein the equalizer jointly detects both desired and co-channel interferer symbols.

6. The method of claim 5 further comprising:

rejecting the co-channel interferer symbols.

7. The method of claim 2, wherein the iterative detection procedure procedure comprises:

estimating a first channel from the received signal, thereby generating a first channel estimate and a first synchronization position;

providing the received signal, the first channel estimate and the first synchronization position to an equalizer, wherein the equalizer performs a first equalization and generates a first estimate of transmitted signals and residuals;

estimating a second channel using the residuals from the first equalization, a synchronization position of the co-channel interferer and a training sequence of the co-channel interferer, thereby generating a second channel estimate;

providing the second channel estimate to the equalizer, wherein the equalizer performs a second equalization over a first part of the desired burst disturbed by the co-channel interferer burst using joint detection based on the first and second channel estimates;

performing a conventional equalization on a second part of the desired burst not disturbed by the co-channel interferer burst; and

generating a second estimate of transmitted symbols from the equalization of the first and second parts of the desired burst.

8. The method of claim 1 further comprising:

selecting a conventional detection procedure when the co-channel interferer has a low signal strength compared to a signal strength of the desired burst.

9. The method of claim 1, wherein the time offset is a difference between a coarse synchronization position for the desired burst and a synchronization position for the co-channel interferer.

10. The method of claim 9, wherein the synchronization position for the co-channel interferer is based on a time of arrival.

11. The method of claim 9, wherein the synchronization position for the co-channel interferer is based on a long time correlation.

12. The method of claim 1 further comprising:

detecting a modulation for the desired burst; and

detecting a modulation for the co-channel interferer.

13. The method of claim 1 further comprising:

detecting a time offset between the desired burst and at least one additional co-channel interferer burst contained in the received signal; and

selecting a detection procedure for the at least one additional co-channel interferer burst based on the time offset between the desired burst and the at least one additional co-channel interferer burst.

14. A receiver comprising:

a front end receiver that outputs a received signal that contains a desired burst and a co-channel interferer burst;

logic that detects a time offset between the desired burst and the co-channel interferer burst; and

logic that selects a detection procedure based on the time offset between the desired burst and the co-channel interferer burst.

15. The receiver of claim 14 further comprising:

logic that selects a joint detection procedure when a training sequence of the desired burst and a training sequence of the co-channel interferer burst overlap each other by at least a first predetermined amount;

if the training sequence of the desired burst and the training sequence of the co-channel interferer do not overlap each other by at least the first predetermined amount, then logic that selects an iterative detection procedure when the training sequence of the co-channel interferer burst overlaps the desired burst by a second predetermined amount; and

logic that selects a conventional detection procedure when the training sequence of the co-channel interferer burst does not overlap the desired burst by at least the second predetermined amount.

16. The receiver of claim 15, wherein the first predetermined amount is about 50%.

17. The receiver of claim 15, wherein the second predetermined amount is about 50%.

18. The receiver of claim 15, wherein the joint detection section comprises:

logic that finds a synchronization position by correlating the training sequences of the desired burst and the co-channel interferer burst with the received burst;

logic that estimates a first channel and a second channel jointly, thereby generating a first channel estimate and a second channel estimate; and

logic that provides the received signal, the first channel estimate, the second channel estimate and the synchronization position to an equalizer, wherein the equalizer jointly detects both desired and co-channel interferer symbols.

19. The receiver of claim 18 further comprising:

logic that rejects the co-channel interferer symbols.

20. The receiver of claim 15, wherein the iterative detection section comprises:

logic that estimates a first channel from the received signal, thereby generating a first channel estimate and a synchronization position;

logic that provides the received burst, the first channel estimate and the synchronization position to an equalizer, wherein the equalizer performs a first equalization and generates a first estimate of desired symbols and residuals;

logic that estimates a second channel using the residuals from the first equalization, a synchronization position of the co-channel interferer and the training sequence of the co-channel interferer, thereby generating a second channel estimate;

logic that provides the second channel estimate to the equalizer, wherein the equalizer performs a second equalization over a first part of the desired burst disturbed by the co-channel interferer burst using joint detection based on the first and second channel estimates;

logic that performs a conventional equalization on a second part of the desired burst not disturbed by the co-channel interferer burst; and

logic that generates a second estimate of desired symbols from the equalization of the first and second parts of the desired burst.

21. The receiver of claim 14 further comprising:

logic that selects a conventional detection section when the co-channel interferer has a low signal strength compared to a signal strength of the desired burst.

22. The receiver of claim 14, wherein the time offset is a difference between a coarse synchronization position for the desired burst and a synchronization position for the co-channel interferer.

23. The receiver of claim 22, wherein the synchronization position for the co-channel interferer is based on a time of arrival.

24. The receiver of claim 22, wherein the synchronization position for the co-channel interferer is based on a long time correlation.

25. The receiver of claim 14 further comprising:

logic that detects a modulation for the desired burst; and

logic that detects a modulation for the co-channel interferer.

26. The receiver of claim 14, wherein the receiver is a base station receiver.

27. The receiver of claim 14, wherein the receiver is a mobile terminal receiver.

28. The receiver of claim 14 further comprising:

logic that detects a time offset between the desired burst and at least one additional co-channel interferer burst contained in the received signal; and

logic that selects a detection procedure for the at least one additional co-channel interferer burst based on the time offset between the desired burst and the at least one additional co-channel interferer burst.