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Abstract

The invention concerns methods and apparatus for performing channel equalization in a direct-sequence spread spectrum communications system. The methods and apparatus of the present invention are particularly applicable in situations where communication occurs over a channel experiencing multipath interference associated with paths having significantly different lengths. The impulse response-delay profile of such a channel is typically sparse, that is, dominated by a relatively few and widely spaced taps or clusters of closely spaced taps. In one aspect, equalization filter coefficients are calculated based on a channel estimate derived from a single cluster of closely-spaced channel taps collectively having the greatest percentage of energy as indicated by the impulse response-delay profile. In another aspect, equalization filter coefficients are calculated for each of two clusters of closely-spaced channel taps, where the two clusters of closely-spaced channel taps are separated by a delay spread indicative of a sparse channel. In a further aspect where channel equalization coefficients are calculated for each of two clusters of closely-spaced channel taps, the equalization coefficients are jointly optimized during the calculation process.

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First Claim