Cancellation of interference in a communication system with application to S-CDMA
First Claim
1. An apparatus, comprising:
- a transmitter that produces a spread signal that includes a numerically constant-valued symbol spread across a first plurality of codes and data spread across a second plurality of codes and transmits the spread signal across a communication link;
a receiver that receives the spread signal after being transmitted across the communication link, the spread signal comprising interference, the receiver includes;
a vector de-spreader that employs the first plurality of codes and the second plurality of codes to de-spread the spread signal;
a weight computation functional block that calculates a plurality of complex-valued combining weights using the spread signal and the interference of the spread signal; and
a linear combiner that scales the de-spread signal portions, that are de-spread using the first plurality of codes, using the plurality of complex-valued combining weights and combines the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal.
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Accused Products
Abstract
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 are 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
82 Claims
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1. An apparatus, comprising:
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a transmitter that produces a spread signal that includes a numerically constant-valued symbol spread across a first plurality of codes and data spread across a second plurality of codes and transmits the spread signal across a communication link; a receiver that receives the spread signal after being transmitted across the communication link, the spread signal comprising interference, the receiver includes; a vector de-spreader that employs the first plurality of codes and the second plurality of codes to de-spread the spread signal; a weight computation functional block that calculates a plurality of complex-valued combining weights using the spread signal and the interference of the spread signal; and a linear combiner that scales the de-spread signal portions, that are de-spread using the first plurality of codes, using the plurality of complex-valued combining weights and combines the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal. - 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 employs a first plurality of codes and a second plurality of codes to de-spread a spread signal, the spread signal includes interference; a weight computation functional block that calculates a plurality of complex-valued combining weights using the spread signal and the interference of the spread signal; and a linear combiner that scales the de-spread signal portions, that are de-spread using the first plurality of codes, using the plurality of complex-valued combining weights and combines the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An apparatus, comprising:
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a vector de-spreader that employs a first plurality of codes and a second plurality of codes to de-spread a spread signal; a weight computation functional block that calculates a plurality of complex-valued combining weights using the spread signal and interference contained within the spread signal; a linear combiner that scales the de-spread signal portions, that are de-spread using the first plurality of codes, using the plurality of complex-valued combining weights and selectively sums the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal; and an iterative adaptive weight functional block that is operable to perform error calculation of a hard decision corresponding to the at least one signal portion of the spread signal; and wherein the iterative adaptive weight functional block updates the plurality of complex-valued combining weights using the calculated error. - View Dependent Claims (22, 23, 24, 25)
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26. An apparatus, comprising:
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a transmitter that is operable to produce a spread signal that includes a first symbol spread across a first plurality of codes and a second symbol spread across a second plurality of codes and that is operable to transmit the spread signal across a communication link; wherein the first symbol has a first modulation type and the second symbol has a second modulation type such that the first modulation type is of a lower-order modulation type than the second modulation type; a receiver that is operable to receive the spread signal after being transmitted across the communication link, the spread signal received at the receiver including interference, the receiver comprising; a vector de-spreader that is operable to employ the first plurality of codes and the second plurality of codes to de-spread the spread signal; and a linear combiner that is operable to scale the de-spread signal portions, that are de-spread using the first plurality of codes, using a plurality of complex-valued combining weights and that is operable to combine the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. An apparatus, comprising:
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a transmitter that is operable to produce a spread signal that includes a first symbol spread across a first plurality of codes and a second symbol spread across a second plurality of codes and that is operable to transmit the spread signal across a communication link; wherein the first plurality of codes and the second plurality of codes are arranged into a code matrix; wherein, within the transmitter, the code matrix is reordered from its original order to a modified order according to a predetermined reordering pattern before the predetermined symbol is spread across a first plurality of codes and the data symbol is spread across a second plurality of codes; a receiver, communicatively coupled to the transmitter via the communication link, that receives the spread signal after being transmitted across the communication link, the spread signal comprising interference, the receiver comprising; a vector de-spreader that is operable to employ the first plurality of codes and the second plurality of codes to de-spread the spread signal; wherein, within the receiver, the code matrix is reverse reordered from its modified order to the original order according to the predetermined reordering pattern before the vector de-spreader employs the first plurality of codes and the second plurality of codes to de-spread the spread signal; and a linear combiner that is operable to scale the de-spread signal portions, that are de-spread using the first plurality of codes, using the plurality of complex-valued combining weights and that is operable to combine the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61)
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62. 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 includes a first symbol that has been spread across the first plurality of codes and a second symbol that has been spread across the second plurality of codes; a memory that includes a plurality of pre-computed complex-valued combining weights; and a linear combiner that is operable to scale the de-spread signal portions, that are de-spread using the first plurality of codes;
using the plurality of pre-computed complex-valued combining weights and that is operable to combine the scaled, de-spread signal portions that are de-spread using the first plurality of codes and one signal portion that is de-spread using one code selected from the second plurality of codes to perform interference cancellation on at least one additional signal portion that is de-spread from the spread signal. - View Dependent Claims (63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82)
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Specification