Method and apparatus for canceling spread-spectrum noise

• US 5,325,394 A
• Filed: 03/03/1993
• Issued: 06/28/1994
• Est. Priority Date: 06/29/1992
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Bruckert, Eugene
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/025,705
• Time in Patent Office: 482 Days
• Field of Search: 375/1, 375/58, 375/102, 455/65, 342/384
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 2001/71077 Partial interference cancellation

Abstract

A spread-spectrum noise canceller (182) is provided. A received phase and a received amplitude for a first (216) and a second (236) component of a received spread-spectrum signal (200) is determined. The second component (236) is structurally similar to [a replica of] the first component (216), but differs by being received at a different time, being transmitted along a different path, or having a different phase [which was received at a different time]. In addition, the spread-spectrum signal (200) includes a first and a second known signal. A portion of a spread-spectrum noise signal in the received signal (200) is canceled by generating an estimated signal (270) by spreading (260) the second known signal at the second component received phase (204) with the first known signal at the first component received phase (224) and adjusting a gain (268) of an integrated form of the spread second known signal as a function of the received amplitudes of the first (216) and the second (236) components. Subsequently, the second known signal is processed out of the received spread-spectrum signal (200) by subtracting (166) the estimated signal (270) from a demodulated form (216, 236) of the received spread-spectrum signal (200).

Claims

1. An apparatus comprising a spread-spectrum noise canceller, the spread-spectrum noise canceller comprising:

(a) determining means for determining a received phase and a received amplitude for a first and a second component of a received spread-spectrum signal, the first component being different from the second component, the spread-spectrum signal including a first and a second known signal; and

(b) noise cancelling means, operatively coupled to the determining means, for cancelling a portion of a spread-spectrum noise signal in the received spread-spectrum signal by;

(i) generating an estimated signal by spreading the second known signal at the second component received phase with the first known signal at the first component received phase and adjusting a gain of an integrated form of the spread second known signal as a function of the received amplitudes of the first and the second components; and

(ii) processing the second known signal out of the received spread-spectrum signal by subtracting the estimated signal from a demodulated form of the received spread-spectrum signal.

2. The apparatus of claim 1 wherein the spread-spectrum noise canceller cancelling means processes the second known signal out of the received spread-spectrum signal only if the adjusted gain of the integrated form of the spread second known signal is greater than a predetermined threshold.

3. The apparatus of claim 1 wherein the spread-spectrum noise canceller cancelling means generates the estimated signal by further spreading the second known signal at the second component received phase with a channel selecting spreading code at the first component received phase.

4. The apparatus of claim 1 further comprising:

(a) descrambling means, operatively coupled to the spread-spectrum noise canceller, for descrambling the processed demodulated form of the received spread-spectrum signal by utilizing a known spreading code;

(b) deinterleaving means, operatively coupled to the descrambling means, for deinterleaving the descrambled received spread-spectrum signal within a predetermined size block; and

(c) decoding means, operatively coupled to the deinterleaving means, for generating at least one estimated data bit by utilizing maximum likelihood decoding techniques to derive the at least one estimated data bit from the deinterleaved received spread-spectrum signal.

5. The apparatus of claim 4 wherein the decoding means comprises means for generating at least one estimated data bit by utilizing maximum likelihood decoding techniques which are substantially similar to the Viterbi decoding algorithm.

6. An apparatus comprising a spread-spectrum noise canceller, the spread-spectrum noise canceller comprising:

(a) receiving means for receiving a spread-spectrum signal having a first and a second component from over a communication channel, the first component being different from the second component, the spread-spectrum signal including a first and a second known signal;

(b) determining means, operatively coupled to the receiving means, for determining a received phase and a received amplitude for the first and the second components of a received spread-spectrum signal;

(c) demodulating means, operatively coupled to the receiving means, for demodulating the received spread-spectrum signal; and

(d) noise cancelling means, operatively coupled to the determining means and the demodulating means, for cancelling a portion of a spread-spectrum noise signal in the received spread-spectrum signal by;

(i) generating an estimated signal by spreading the second known signal at the second component received phase with the first known signal at the first component received phase, integrating the spread second known signal over a predetermined time, and adjusting a gain of the integrated spread second known signal as a function of the received amplitudes of the first and the second components; and

(ii) processing the second known signal out of the received spread-spectrum signal by subtracting the estimated signal from the demodulated received spread-spectrum signal.

7. The apparatus of claim 6 wherein the spread-spectrum noise canceller canceling means processes the second known signal out of the received spread-spectrum signal only if the adjusted gain of the integrated form of the spread second known signal is greater than a predetermined threshold.

8. The apparatus of claim 6 wherein the spread-spectrum noise canceller canceling means generates an estimated signal by further spreading the second known signal at the second component received phase with a channel selecting spreading code at the first component received phase.

9. The apparatus of claim 6 further comprising:

(a) descrambling means, operatively coupled to the spread-spectrum noise canceller, for descrambling the processed demodulated form of the received spread-spectrum signal by utilizing a known spreading code;

(b) deinterleaving means, operatively coupled to the descrambling means, for deinterleaving the descrambled received spread-spectrum signal within a predetermined size block; and

(c) decoding means, operatively coupled to the deinterleaving means, for generating at least one estimated data bit by utilizing maximum likelihood decoding techniques to derive the at least one estimated data bit from the deinterleaved received spread-spectrum signal.

10. The apparatus of claim 6 wherein the communication channel is selected from the group consisting essentially of an electronic data bus, radio communication link, wireline and optical fiber link.

11. A spread-spectrum signal processing method, comprising:

(a) determining a received phase and a received amplitude for a first and a second component of a received spread-spectrum signal, the first component being different from the second component, the spread-spectrum signal including a first and a second known signal; and

(b) canceling a portion of a spread-spectrum noise signal in the received spread-spectrum signal by;

(i) generating an estimated signal by spreading the second known signal at the second component received phase with the first known signal at the first component received phase and adjusting a gain of an integrated form of the spread second known signal as a function of the received amplitudes of the first and the second components; and

(ii) processing the second known signal out of the received spread-spectrum signal by subtracting the estimated signal from a demodulated form of the received spread-spectrum signal.

12. The method of claim 11 wherein the step of canceling comprises processing the second known signal out of the received spread-spectrum signal only if the adjusted gain of the integrated form of the spread second known signal is greater than a predetermined threshold.

13. The method of claim 11 wherein the step of canceling comprises generating the estimated signal by further spreading the second known signal at the second component received phase with a channel selecting spreading code at the first component received phase.

14. The method of claim 11 further comprising:

(a) descrambling the processed demodulated form of the received spread-spectrum signal by utilizing a known spreading code;

(b) deinterleaving the descrambled received spread-spectrum signal within a predetermined size block; and

(c) generating at least one estimated data bit by utilizing maximum likelihood decoding techniques to derive the at least one estimated data bit from the deinterleaved received spread-spectrum signal.

15. The method of claim 14 wherein the step of generating at least one estimated data bit comprises utilizing maximum likelihood decoding techniques which are substantially similar to the Viterbi decoding algorithm.

16. A spread-spectrum signal processing method, comprising:

(a) receiving a spread-spectrum signal having a first and a second component from over a communication channel, the first component being different from the second component, the spread-spectrum signal including a first and a second known signal;

(b) determining a received phase and a received amplitude for the first and the second components of a received spread-spectrum signal;

(c) demodulating the received spread-spectrum signal; and

(d) canceling a portion of a spread-spectrum noise signal in the received spread-spectrum signal by;

(i) generating an estimated signal by spreading the second known signal at the second component received phase with the first known signal at the first component received phase, integrating the spread second known signal over a predetermined time, and adjusting a gain of the integrated spread second known signal as a function of the received amplitudes of the first and the second components; and

(ii) processing the second known signal out of the received spread-spectrum signal by subtracting the estimated signal from the demodulated received spread-spectrum signal.

17. The method of claim 16 wherein the step of canceling comprises processing the second known signal out of the received spread-spectrum signal only if the adjusted gain of the integrated form of the spread second known signal is greater than a predetermined threshold.

18. The method of claim 16 wherein the step of canceling comprises generating the estimated signal by further spreading the spread known signal at the second component received phase with a channel selecting spreading code at the first component received phase.

19. The method of claim 16 further comprising:

(a) descrambling the processed demodulated form of the received spread-spectrum signal by utilizing a known spreading code;

(b) deinterleaving the descrambled received spread-spectrum signal within a predetermined size block; and

(c) generating at least one estimated data bit by utilizing maximum likelihood decoding techniques to derive the at least one estimated data bit from the deinterleaved received spread-spectrum signal.

20. The method of claim 19 wherein the communication channel is selected from the group consisting essentially of an electronic data bus, radio communication link, wireline and optical fiber link.