Method for iterative interference cancellation for co-channel multi-carrier and narrowband systems

• US 8,155,595 B2
• Filed: 01/05/2010
• Issued: 04/10/2012
• Est. Priority Date: 03/06/2009
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Sahin, Mustafa E., Guvenc, Ismail, Arslan, Huseyin
• Primary Examiner(s): Hoang, Thai
• Application Number:
  US12/652,337
• Publication Number:
  US 20100226356A1
• Time in Patent Office: 826 Days
• Field of Search: 455501-506, 455 631- 634, 455/65, 455/67.13, 4551142-1143, 455/296, 455298-312, 375/144, 375/148, 375260-264
• US Class Current: 455/63.2
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04J 11/0066 of narrowband interference narrowband interference reduction H04B1/1036
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/03821 Inter-carrier interference cancellation [ICI]
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT

Abstract

In a co-channel deployment of narrowband and multi-carrier technologies (e.g., a femtocell and a macrocell), a method provides cancelling of interference which treats the co-channel signals as desired signals and enhances each of them iteratively. At each iteration, each signal is demodulated and regenerated based on symbol decisions already made and a predetermined channel impulse response. To estimate the other (interfering) co-channel signal, the regenerated signal is subtracted from the aggregate signal. Simulations have shown that a method of the present invention can provide fundamental improvement in the performances of both interfering systems in as few as two iterations. The fundamental performance gain that can be obtained outweigh the required computational burden.

Claims

1. A method for canceling interference between a multicarrier signal and a narrowband signal from a received signal, comprising:

(a) from an estimate of a narrowband signal, obtaining a regenerated narrowband signal by eliminating random noise from the estimate of the narrowband signal;

(b) obtaining the spectrum of the regenerated narrowband signal;

(c) obtaining an estimate of the spectrum of the multicarrier signal by subtracting a spectrum of the regenerated narrowband signal from a spectrum of the received signal;

(d) from the estimates of multicarrier signals, obtaining a regenerated spectrum of the multicarrier signal;

(e) obtaining a refined estimate of the narrowband signal by subtracting a time domain representation of the regenerated spectrum of the multicarrier signal from the received signal;

(f) using the refined estimate of the narrowband signal to be the estimate of the narrowband signal of step (a), repeat steps (a) to (e) for a predetermined number of iterations; and

(g) after completing the predetermined number of iterations, recovering the data from the latest regenerated spectrum of the multicarrier signal or the narrowb and signal.

2. A method as in claim 1, wherein the multicarrier signal comprises a signal of an OFDMA system.

3. A method as in claim 2, wherein the OFDMA system is an LTE system.

4. A method as in claim 2, wherein the OFDMA system comprises a multi-carrier ultrawideband system.

5. A method as in claim 1, wherein the narrowband signal comprises a signal of a W-CDMA system.

6. A method as in claim 1, wherein obtaining the regenerated narrowband signal comprises demodulating the estimate of the narrowband signal and making symbol decisions from results of the demodulation.

7. A method as in claim 1, wherein obtaining the regenerated spectrum of the multicarrier signal comprises making symbol decisions from the subcarriers of the estimate of the spectrum of the multicarrier signal.

8. A method as in claim 1, wherein the spectrum of the received signal is obtained using a fast fourier transform of the received signal.

9. A method as in claim 1, wherein the spectrum of the regenerated narrowband signal is obtained using a fast fourier transform of the regenerated narrow band signal.

10. A method as in claim 1, wherein the time domain representation of the regenerated spectrum of the multicarrier signal is obtained using an inverse fast fourier transform of the regenerated spectrum of the multicarrier signal.

11. A method as in claim 1, wherein the multicarrier signal comprises a signal of a single-carrier FDMA system.

12. A method as in claim 1, wherein the narrowband signal is one of multiple narrowband signals.

13. A method as in claim 12, where the receiver iteratively cancels each narrowband user signal in the time domain.

14. A method as in claim 12, where the iteration subtracts the strongest remaining narrowband interferer from the total signal at each iteration.

15. A method as in claim 1, further comprising synchronizing to the multi-carrier symbols.

16. A method as in claim 1, where the regenerated spectrum of the multicarrier signal spans is obtained by processing the estimated spectrum of the multicarrier signal.

17. A method as in claim 1, further comprising processing only an overlap in frequency between the narrowband signal and the multicarrier signal.

18. A mobile station, comprising:

a receiver which carries out a method for canceling interference between a multicarrier signal and a narrowband signal from a received signal, the method comprising;

(a) from an estimate of a narrowband signal, obtaining a regenerated narrowband signal by eliminating random noise from the estimate of the narrowband signal;

(c) obtaining an estimate of the spectrum of the multicarrier signal by subtracting a spectrum of the regenerated narrowband signal from a spectrum of the received signal;

(d) obtaining a regenerated spectrum of the multicarrier signal;

(e) obtaining a refined estimate of the narrowband signal by subtracting a time domain representation of the regenerated spectrum of the multicarrier signal from the received signal;

(f) using the refined estimate of the narrowband signal to be the estimate of the narrowband signal of step (a), repeat steps (a) to (e) for a predetermined number of iterations; and

(g) after completing the predetermined number of iterations, recovering the data from the latest regenerated spectrum of the multicarrier signal.

19. A mobile station as in claim 18, wherein the multicarrier signal comprises a signal of an OFDMA system.

20. A mobile station as in claim 19, wherein the OFDMA system is an LTE system.

21. A mobile station as in claim 18, wherein the narrowband signal comprises a signal of a W-CDMA system.

22. A mobile station as in claim 18, wherein obtaining the regenerated narrowband signal comprises demodulating the estimate of the narrowband signal and making symbol decisions from results of the demodulation.

23. A mobile station as in claim 18, wherein obtaining the regenerated spectrum of the multicarrier signal comprises making symbol decisions from the subcarriers of the estimate of the spectrum of the multicarrier signal.

24. A mobile station as in claim 18, wherein the spectrum of the received signal is obtained using a fast fourier transform of the received signal.

25. A mobile station as in claim 18, wherein the spectrum of the regenerated narrowband signal is obtained using a fast fourier transform of the regenerated narrow band signal.

26. A mobile station as in claim 18, wherein the time domain representation of the regenerated spectrum of the multicarrier signal is obtained using an inverse fast fourier transform of the regenerated spectrum of the multicarrier signal.