Method and apparatus for channel amplitude estimation and interference vector construction
First Claim
1. A method for signal processing comprising:
- performing a first fast Walsh transform on a first set of magnitudes to obtain a result;
modifying the said result to obtain a first modified result;
performing at least a second fast Walsh transform on the said first modified result to obtain a second modified result;
where modifying the said result comprises;
storing a result of said performing a first fast Walsh transform in a first register;
comparing each magnitude comprising said result of performing said at least a first fast Walsh transform to a threshold value; and
replacing each magnitude of said stored result of performing said first fast Walsh transform that is greater than said threshold value with a zero to obtain the first modified result.
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Abstract
The present invention is directed to an efficient method and apparatus for channel determination and interference vector construction in accordance with spread spectrum systems. Channel determination is performed using a first series of fast Walsh transform steps. The results of the first set of fast Walsh transform steps corresponding to valid communication system channels are compared to a threshold value. Results derived from the first set of fast Walsh transform steps are then passed through a second set of fast Walsh transform steps with the number of steps performed for a set of results determined by the symbol length associated with the channels from which the amplitude information was derived. The interference vectors thus obtained for each valid symbol length may then be combined to form a composite interference vector. The fast Walsh transform steps and other steps may be performed using shared hardware components or software modules.
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Citations
21 Claims
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1. A method for signal processing comprising:
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performing a first fast Walsh transform on a first set of magnitudes to obtain a result; modifying the said result to obtain a first modified result; performing at least a second fast Walsh transform on the said first modified result to obtain a second modified result; where modifying the said result comprises; storing a result of said performing a first fast Walsh transform in a first register; comparing each magnitude comprising said result of performing said at least a first fast Walsh transform to a threshold value; and replacing each magnitude of said stored result of performing said first fast Walsh transform that is greater than said threshold value with a zero to obtain the first modified result.
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2. An apparatus for interference cancellation, comprising:
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means for receiving a signal; means for despreading the received signal; means for performing carrier phase recovery on the despread signal; means for performing at least a first fast Walsh transform on the despread carrier phase recovered signal to obtain a first set of transformed values; means for modifying the said first set of transformed values to create a first modified set of values; and means for performing at least a second fast Walsh transform on said first modified set of values to create a second modified set of values, further comprising; means for storing an interference vector precursor, wherein said interference vector precursor includes an element amplitude for an element having an amplitude that exceeds a threshold and a zero for an element having an amplitude that does not exceed said threshold. - View Dependent Claims (3, 4, 5, 6)
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7. A receiver device, comprising:
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a despreader operable to despread a received signal to produce a despread signal; a carrier phase recovery module coupled to the despreader; a fast Walsh transform module operable to perform a selected fast Walsh transform stage on the output of the carrier phase recovery module; a comparator operable to compare each value output from said fast Walsh transform module to a threshold; a first memory register operable to store element values output from said comparator as having a value less than said threshold; and a second memory register operable to store element values output from said comparator as having a value not less than said threshold. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method implemented in a logic circuit configured for:
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performing carrier phase recovery on and despreading a received signal to obtain a first set of magnitudes; performing at least a first fast Walsh transform on said first set of magnitudes, wherein said set of magnitudes contains a number of magnitudes that is equal to a number of chips in a longest valid symbol; storing a result of said performing at least a first fast Walsh transform in a first register; comparing each magnitude comprising said result of performing said at least a first fast Walsh transform to a threshold value; and storing each magnitude of said stored result of performing said first fast Walsh transform that is greater than said threshold value to obtain a first modified result, further configured for; storing each magnitude comprising said result of performing an nth fast Walsh transform having a magnitude that is not less than said threshold value in a second register; and storing a zero for magnitudes comprising said result of performing said nth fast Walsh transform having a magnitude that is less than said threshold value in said second register, wherein said second register comprises a number of magnitudes that is equal to said number of chips in a longest valid symbol, and wherein n is a number of fast Walsh transforms performed. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
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Specification