Remote terminal spread spectrum CDMA subtractive interference canceller

• US 7,242,675 B2
• Filed: 07/24/2002
• Issued: 07/10/2007
• Est. Priority Date: 04/22/1993
• Status: Expired due to Fees

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Schilling, Donald L., Kowalski, John
• Primary Examiner(s): Pham; Chi
• Assistant Examiner(s): Boakye; Alexander O.
• Application Number:
  US10/201,797
• Publication Number:
  US 20020186673A1
• Time in Patent Office: 1,812 Days
• Field of Search: 370/342, 370/335, 370/310, 370/479, 370/331, 370/332, 370/441, 375/343, 375/347, 375/346, 375/206, 375/207
• US Class Current: 370/335
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/71075 Parallel interference cancellation

Abstract

A spread-spectrum code division multiple access interference canceller employed by a remote terminal for reducing interference in a direct sequence CDMA receiver having N chip-code channels. The interference canceller includes a plurality of correlators or matched filters, a plurality of spread-spectrum-processing circuits, subtracting circuits, and channel correlators or channel-matched filters. Using a plurality of chip-code signals, the correlators despread the spread-spectrum CDMA signal as despread signals, respectively. The spread-spectrum-processing circuits use a timed version of the chip-code signals, for spread-spectrum processing the despread signals, respectively, with a chip-code-signal corresponding to a respective despread signal. For recovering a code channel using an i^th chip-code-signal, the subtracting circuits subtracts from the spread-spectrum CDMA signal, each of the N-1 spread-spectrum-processed-despread signals thereby generating a subtracted signal. The N-1 spread-spectrum-processed-despread signals do not include the spread-spectrum-processed-despread signal of the i^th channel. The channel correlator or channel-matched filter despreads the subtracted signal.

Claims

1. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA signal having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of means for generating a plurality of chip-code signals;

a plurality of despreading means, with each of said despreading means responsive to the respective distinct chip-code signal identifying a corresponding one of the N channels, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of delay means providing proper timing for the plurality of chip-code signals;

a plurality of means, responsive to the plurality of delayed chip-code signals, for simultaneously spread-spectrum processing the plurality of despread signals, respectively, with a chip-code-signal corresponding to a respective despread signal;

means, for an i^th chip-code signal, for simultaneously subtracting from the spread-spectrum CDMA signal, each of N-1 spread-spectrum-processed-despread signals, with the N-1 spread-spectrum-processed-despread signals excluding a spread-spectrum processed-despread signal of the i^th despread signal, thereby generating a subtracted signal; and

channel means for despreading the subtracted signal with the i^th chip-code signal as an i^th channel.

2. The remote terminal canceller of claim 1 wherein each of said plurality of despreading means includes:

a filter;

a chip-code generator for generating a chip-code signal from a respective chip codeword; and

a mixer coupled between said filter and said chip-code generator.

3. The remote terminal canceller of claim 2 wherein said channel means includes:

a filter;

a chip-code generator for generating a chip-code signal from a chip codeword corresponding to the i^th channel; and

a mixer coupled between said filter and said chip-code generator.

4. The remote terminal canceller of claim 1 wherein each of said plurality of despreading means includes a matched filter having an impulse response matched to a respective chip code-word.

5. The remote terminal canceller of claim 4 wherein said channel means includes:

a filter;

a chip-code generator for generating a chip-code signal from a chip codeword corresponding to the i^th channel; and

a mixer coupled between said filter and said chip-code generator.

6. The remote terminal canceller of claim 4 wherein said channel-despreading means includes a matched filter having an impulse response matched to a chip codeword corresponding to the i^th channel.

7. The remote terminal canceller of claim 1 wherein said channel means includes:

a filter;

a chip-code generator for generating a chip-code signal from a chip codeword corresponding to the i^th channel; and

a mixer coupled between said filter and said chip-code generator.

8. The remote terminal canceller of claim 1 wherein each of said despreading means includes a digital signal processor with a digital filter having an impulse response matched to a respective chip codeword.

9. The remote terminal canceller of claim 8 wherein said channel-despreading means includes a matched filter having an impulse response matched to a chip codeword corresponding to the i^th channel.

10. The remote terminal canceller of claim 8 wherein said channel-despreading means includes a surface acoustic wave (SAW) device having an impulse response matched to a chip codeword corresponding to the i^th channel.

11. The remote terminal canceller of claim 1 wherein said channel-despreading means includes a digital signal processor with digital matched filter having an impulse response matched to a chip codeword corresponding to the i^th channel.

12. The remote terminal canceller of claim 1 wherein each of said plurality of despreading means includes a surface acoustic wave (SAW) device having an impulse response matched to a chip codeword corresponding to the i^th channel.

13. The remote terminal canceller of claim 12 wherein said channel despreading means includes a matched filter having an impulse response matched to a chip codeword corresponding to the i^th channel.

14. The remote terminal canceller of claim 12 wherein said channel despreading means includes a chip-code generator for generating a chip-code signal from a digital matched filter having an impulse response matched to a chip codeword corresponding to the i^th channel.

15. The remote terminal canceller of claim 12 wherein said channel despreading means includes a surface acoustic wave (SAW) device having an impulse response matched to a chip codeword corresponding to the i^th channel.

16. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA signal having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of chip-code-signal generators for generating, simultaneously, a plurality of chip-code signals;

a plurality of correlators, responsive to a plurality of distinct chip-code signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of delay devices coupled to said plurality of chip-code signal generators to provide proper timing for the plurality of chip-code signals as a timed plurality of chip-code signals, respectively;

a plurality of mixers, responsive to the timed plurality of chip-code signals, for simultaneously spread-spectrum processing, the plurality of despread signals, respectively, with a chip-code-signal corresponding to a respective despread signal;

a subtractor, for an i^th chip-code signal, for simultaneously subtracting from the spread-spectrum CDMA signal, each of the N-1 spread-spectrum-processed-despread signals, with the N-1 spread-spectrum-processed-despread signals, excluding a spread-spectrum processed despread signal of the i^th despread signal, thereby generating a subtracted signal; and

a channel correlator for despreading the subtracted signal with the i^th chip-code signal as an i^th channel.

17. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA signal having N chip-code channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of matched filters, responsive to a plurality of distinct chip-code signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of chip-code-signal generators, responsive to a plurality of despread signals from the plurality of matched filters, for generating a timed plurality of chip-code signals, respectively;

a plurality of mixers, responsive to the plurality of despread signals from the plurality of matched filters and the timed plurality of chip-code signals from the plurality of chip-code-signal generators, respectively, for spread-spectrum processing, simultaneously, the plurality of despread signals, respectively, with a timed chip-code signal corresponding to a respective despread signal;

a subtractor, for an i^th chip-code signal, for subtracting from the spread-spectrum CDMA signal, simultaneously, each of the N-1 spread-spectrum-processed-despread signals, with the N-1 spread-spectrum-processed-despread signals not including a spread-spectrum processed despread signal of the i^th despread signal, thereby generating a subtracted signal; and

a channel matched filter for despreading the subtracted signal with the i^th chip-code signal as an i^th channel.

18. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA signal having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of chip-code-signal generators for generating, simultaneously, a plurality of chip-code signals;

a plurality of correlators, responsive to a plurality of distinct chip-code-signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of delay devices coupled to said plurality of chip-code signal generators to provide proper timing for the plurality of chip-code signals as a timed plurality of chip-code signals, respectively;

a plurality of mixers, responsive to the timed plurality of chip-code signals, for simultaneously spread-spectrum processing the plurality of despread signals, respectively, with a chip-code-signal corresponding to a respective despread signal, producing N spread-spectrum-processed-despread signals;

a plurality of subtractors, each of said plurality of subtractors for subtracting from the spread-spectrum CDMA signal all but a particular one of the N spread-spectrum-processed-despread signals, with the particular one of the N spread-spectrum-processed-despread signals being different for each of said plurality of subtractors, thereby generating a plurality of subtracted signals; and

a plurality of channel correlators for despreading the plurality of subtracted signals with a particular one of the plurality of chip-code signals, respectively, as a plurality of channels.

19. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA signal having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of chip-code-signal generators for generating, simultaneously, a plurality of chip-code signals;

a plurality of correlators, responsive to a plurality of distinct chip-code-signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of delay devices coupled to said plurality of chip-code-signal generators to provide proper timing for the plurality of chip-code signals as a timed plurality of chip-code signals, respectively;

a plurality of mixers, responsive to the timed plurality of chip-code signals, for simultaneously spread-spectrum processing the plurality of despread signals, respectively, with a chip-code signal corresponding to a respective despread signal, producing N spread-spectrum-processed-despread signals;

a first subtractor, for subtracting from the spread-spectrum CDMA signal, all but a first one of the N spread-spectrum-processed-despread signals,

a plurality of chip-code-signal generators, responsive to a plurality of despread signals from the plurality of matched filters, for generating, simultaneously, a timed plurality of chip-code signals, respectively;

a plurality of mixers, responsive to the plurality of despread signals from the plurality of matched filters and the timed plurality of chip-code signals from the plurality of chip-code signal generators, respectively, for simultaneously spread-spectrum processing the plurality of despread signals, respectively, with a timed chip-code signal corresponding to a respective despread signal, producing N spread-spectrum-processed-despread signals;

a plurality of subtractors, each of said plurality of subtractors for subtracting from the spread-spectrum CDMA signal all but a particular one of the N spread-spectrum-processed-despread signals, with the particular one of the N spread-spectrum-processed-despread signals being different for each of said plurality of subtractors, thereby generating a plurality of subtracted signals; and

a plurality of channel-matched filters for despreading the plurality of subtracted signals with a particular one of the plurality of distinct chip-code signals, respectively, as a plurality of channels.

20. A remote terminal spread-spectrum code division multiple access (CDMA) interference canceller for reducing interference in a received spread-spectrum CDMA receiver signal having N channels, with each of the N channels identified by a distinct chip-code signal, comprising:

a plurality of matched filters, responsive to a plurality of distinct chip-code-signals, for simultaneously despreading a plurality of spread-spectrum channels of a spread-spectrum CDMA signal as a plurality of despread signals, respectively;

a plurality of chip-code signal generators, responsive to a plurality of despread signals from the plurality of matched filters, for simultaneously generating a timed plurality of chip-code-signals generators, respectively;

a plurality of mixers, responsive to the plurality of despread signals from the plurality of matched filters and the timed plurality of chip-code signals from the plurality of chip-code-signal generators, respectively, for simultaneously spread-spectrum processing the plurality of despread signals, respectively, with a timed chip-code signal corresponding to a respective despread signal, producing N spread-spectrum-processed-despread signals;

a first subtractor, for subtracting from the spread-spectrum CDMA signal, all but a first one of the N spread-spectrum-processed-despread signals, thereby generating a first subtracted signal;

a second subtractor, for subtracting from the spread-spectrum CDMA signal, all but a second one of the N spread-spectrum-processed-despread signals, thereby generating a second subtracted signal; and

an n^th subtractor, for subtracting from the spread-spectrum CDMA signal, all but an n^th one of the N spread-spectrum-processed-despread signals, thereby generating an n^th subtracted signal;

a first channel-matched filter for despreading the first subtracted signal with a first chip-code signal as an estimate of a first channel;

a second channel-matched filter for despreading the second subtracted signal with a second chip-code signal as an estimate of a second channel; and

an n^th channel-matched filter for despreading the n^th subtracted signal with an n^th chip-code signal as an estimate of an n^th channel;

espread channels other than that channel.