Acquisition of spreading factors (SFS) of multiple transmitted signals in code division multiple access system

• US 20090060000A1
• Filed: 01/24/2008
• Published: 03/05/2009
• Est. Priority Date: 05/01/2007
• Status: Abandoned Application

• Current Assignee: Broadcom Corporation (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Molev-Shteiman, Arkady, Heiman, Arie
• Application Number:
  US12/019,170
• Publication Number:
  US 20090060000A1
• Time in Patent Office: Days
• US Class Current: 375/130
• CPC Class Codes: H04B 1/71072 Successive interference cancellation
• CPC Class Codes: H04B 2201/70705 Rate detection

Abstract

A method for successive interference cancellation in code division multiple access (CDMA) systems is provided that uses variable interferer weights. This method allows interfering signals to be cancelled in order to recover a transmitted data signal. This method involves receiving the data signal subject to interference from at least one interfering signal. A first interfering signal is identified. Then an interferer weight coefficient associated with the first interfering signal is generated based on its signal strength and SF upon acquisition of the SF. This SF may be monitored such that the Interferer weight may be adjusted when the SF changes based on the detected changes. This allows the first interfering signal to be cancelled from the received data signal using the interferer weight coefficient. These processes may then be reiterated for other interfering signals. It is then possible to recover the transmitted data signal from the received data signal.

Claims

1. A method to acquire spreading factors (SFs) of multiple transmitted signals in code division multiple access system, the method comprising:

receiving a data signal subject to interference from at least one interfering signal;

identifying a first interfering signal;

generating an interferer weight coefficient associated with the first interfering signal based on its signal strength and SF upon acquisition of the SF;

monitoring the SF such that the Interferer weight may be adjusted when the SF changes based on the detected changes;

canceling the first interfering signal from the received data signal using the interferer weight coefficient; and

recovering the transmitted data signal from the received data signal.

2. The method of claim 1, further comprising:

comparing a quality condition associated with the received data signal to a predetermined threshold;

identifying an additional interfering signal;

generating an additional interferer signal weight associated with the additional interfering signal;

canceling the additional interfering signal from the received data signal using the additional interferer signal weight.

3. The method of claim 2, further comprising:

continuing to identify and cancel additional interfering signals from the received data signal until the quality condition compares favorably to the predetermined threshold.

4. The method of claim 1, further comprising:

generating an additional interferer signal weight associated with the additional interfering signal; and

canceling the additional interfering signal from the received data signal using the additional interferer signal weight.

5. The method of claim 1, wherein the interferer weight coefficient may be determined based on the probability that interferer will affect a signal of interest within the received data signal.

6. The method of claim 1, wherein the interferer weight coefficient may be determined based on a signal strength associated with the interfering signal.

7. The method of claim 1, wherein interferer weights of previously determined interfering signals may be adjusted based on a determination of subsequent interfering signal weights coefficients.

8. The method of claim 1, wherein:

the steps of;

identifying an interfering signal;

generating an interferer weight coefficient associated with the interfering signal; and

canceling the first interfering signal from the received data signal using the interferer weight coefficient;

are repeated until predetermined criteria are met.

9. The method of claim 8, wherein the predetermined criteria comprise at least one criteria selected from the group consisting of:

the probability (P_er) that interferer will affect a signal of interest within the received data signal falls below a predetermined threshold;

growth of additive noise power; and

a predetermined number of iterations have been completed.

10. The method of claim 9, wherein the probability (P_er) may be reduced by applying spreading factors associated with the interfering signal.

11. An iterative method to acquire spreading factors (SFs) of multiple transmitted signals in code division multiple access system, the method comprising:

receiving a data signal subject to interference from multiple interfering signals;

identifying an interfering signal having a largest probability (P_er) that the interfering signal will affect a signal of interest within the received data signal;

generating an interferer weight coefficient associated with the interfering signal based on its signal strength and SF upon acquisition of the SF;

monitoring the SF such that the Interferer weight may be adjusted when the SF changes based on the detected changes;

canceling the interfering signal from the received data signal using the interferer weight coefficient;

iteratively repeating the above steps for successive interfering signals until predetermined criteria are met; and

recovering the transmitted data signal from the received data signal.

12. The method of claim 11, wherein the predetermined criteria comprises a favorable comparison between the received data signal'"'"'s quality condition compares favorably to a predetermined threshold.

13. The method of claim 11, wherein the interferer weight coefficient may be determined based on the P_er.

14. The method of claim 11, wherein the interferer weight coefficient may be determined based on a signal strength associated with the interfering signal.

15. The method of claim 11, wherein interferer weights of previously determined interfering signals may be adjusted based on a determination of subsequent interfering signal weights coefficients.

16. The method of claim 11, wherein the predetermined criteria comprise at least one criteria selected from the group consisting of:

the probability (P_er) that interferer will affect a signal of interest within the received data signal falls below a predetermined threshold;

growth of additive noise power; and

a predetermined number of iterations have been completed.

17. The method of claim 11, wherein the probability (P_er) may be reduced by applying spreading factors associated with the interfering signal.

18. The method of claim 11, wherein the transmitted data signal conforms to a wireless communication standard or variant of the wireless communication standard selected from the group consisting of:

Code Division Multiple Access (CDMA);

Global System for Mobile communications (GSM);

Time Division Multiple Access (TDMA); and

Orthogonal Frequency Division Multiplexing (OFDM).

19. A receiver operable to recover a transmitted data signal subject to interfering signal(s), the receiver comprising:

an antenna element operable to receive a data signal subject to the interfering signal(s);

a processing module coupled to the antenna element, the processing module operable to;

identify a first interfering signal within the received data signal;

generate an interferer weight coefficient associated with the first interfering signal based on its signal strength and SF upon acquisition of the SF;

monitor the SF such that the Interferer weight may be adjusted when the SF changes based on the detected changes;

cancel the first interfering signal from the received data signal using the interferer weight coefficient; and

recover the transmitted data signal from the received data signal.

20. The receiver of claim 19, the processing module is further operable to:

compare a quality condition associated with the received data signal to a predetermined threshold;

identify an additional interfering signal;

generate an additional interferer signal weight associated with the additional interfering signal; and

cancel the additional interfering signal from the received data signal using the additional interferer signal weight.

21. The receiver of claim 19, the processing module is further operable to:

continue to identify and cancel additional interfering signals from the received data signal until the quality condition compares favorably to the predetermined threshold.

22. The receiver of claim 19, the processing module is further operable to:

generate an additional interferer signal weight associated with the additional interfering signal; and

cancel the additional interfering signal from the received data signal using the additional interferer signal weight.

23. The receiver of claim 19, wherein the interferer weight coefficient may be determined based on the probability that interferer will affect a signal of interest within the received data signal.

24. The receiver of claim 19, wherein the interferer weight coefficient may be determined based on a signal strength associated with the interfering signal.

25. The receiver of claim 19, wherein interferer weights of previously determined interfering signals may be adjusted based on a determination of subsequent interfering signal weights coefficients.