Cancellation of interference in a communication system with application to S-CDMA
First Claim
1. An apparatus, comprising:
- a vector de-spreader that is operable to employ a first plurality of codes and a second plurality of codes to de-spread a spread signal that is received from a communication channel; and
a linear combiner that includes a plurality of feed-forward equalizers; and
wherein;
each feed-forward equalizer of the plurality of feed-forward equalizers includes a tapped delay line and a plurality of combining weights;
each feed-forward equalizer of the plurality of feed-forward equalizers is operable to sum its corresponding de-spread signal portion with delayed and scaled versions of its corresponding de-spread signal portion using the tapped delay line and the plurality of combining weights; and
the linear combiner is operable to sum outputs from each feed-forward equalizer of the plurality of feed-forward equalizers and a signal portion that is de-spread from the spread signal using a code of the second plurality of codes to perform interference cancellation on the signal portion that is de-spread from the spread signal using the code of the second plurality of codes.
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Abstract
Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes is selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.
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Citations
20 Claims
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1. An apparatus, comprising:
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a vector de-spreader that is operable to employ a first plurality of codes and a second plurality of codes to de-spread a spread signal that is received from a communication channel; and
a linear combiner that includes a plurality of feed-forward equalizers; and
wherein;
each feed-forward equalizer of the plurality of feed-forward equalizers includes a tapped delay line and a plurality of combining weights;
each feed-forward equalizer of the plurality of feed-forward equalizers is operable to sum its corresponding de-spread signal portion with delayed and scaled versions of its corresponding de-spread signal portion using the tapped delay line and the plurality of combining weights; and
the linear combiner is operable to sum outputs from each feed-forward equalizer of the plurality of feed-forward equalizers and a signal portion that is de-spread from the spread signal using a code of the second plurality of codes to perform interference cancellation on the signal portion that is de-spread from the spread signal using the code of the second plurality of codes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus, comprising:
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a vector de-spreader that is operable to employ a first plurality of codes and a second plurality of codes to de-spread a spread signal that is received from a communication channel; and
a plurality of feed-forward equalizers such that such that there is a one to one correspondence between each code of the first plurality of codes and each feed-forward equalizer of the plurality of feed-forward equalizers; and
wherein;
each feed-forward equalizer of the plurality of feed-forward equalizers includes a tapped delay line and a plurality of combining weights;
each feed-forward equalizer of the plurality of feed-forward equalizers is operable to sum its corresponding de-spread signal portion with delayed and scaled versions of its corresponding de-spread signal portion using the tapped delay line and the plurality of combining weights; and
an adder that is operable to sum outputs from each feed-forward equalizer of the plurality of feed-forward equalizers and a signal portion that is de-spread from the spread signal using a code of the second plurality of codes to perform interference cancellation on the signal portion that is de-spread from the spread signal using the code of the second plurality of codes. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method, comprising:
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employing a first plurality of codes and a second plurality of codes to de-spread a spread signal that is received from a communication channel; and
feed-forward equalizing a first plurality of de-spread signal portions that is de-spread from the spread signal using the first plurality of codes;
summing each de-spread signal portion of the first plurality of de-spread signal portions, after undergoing feed-forward equalizing, and a de-spread signal portion that is de-spread from the spread signal using a code of the second plurality of codes to perform interference cancellation on the de-spread signal portion that is de-spread from the spread signal using the code of the second plurality of codes. - View Dependent Claims (18, 19, 20)
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Specification