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Abstract

A fast correlator transform (FCT) algorithm and methods and systems for implementing same, correlate an encoded data word (X.sub.0-X.sub.M-1) with encoding coefficients (C.sub.0-C.sub.M-1), wherein each of (X.sub.0-X.sub.M-1) is represented by one or more bits and each said coefficient is represented by one or more bits, wherein each coefficient has k possible states, and wherein M is greater than 1. In accordance with the invention, X.sub.0 is multiplied by each state (C.sub.0(0)through C.sub.0(k-1)) of the coefficient C.sub.0, thereby generating results X.sub.0C.sub.0(0) through X.sub.0C.sub.0(k-1). This is repeating for data bits (X.sub.1-X.sub.M-1) and corresponding coefficients (C.sub.1-C.sub.M-1), respectively. The results are grouped into N groups. Members of each of the N groups are added to one another, thereby generating a first layer of correlation results. The first layer of results is grouped and the members of each group are summed with one another to generate a second layer of results. This process is repeated as necessary until a final layer of results is generated. The final layer of results includes a separate correlation output for each possible state of the complete set of coefficients (C.sub.0-C.sub.M-1). The final layer of results is compared to identify a most likely code encoded on said data word. In an embodiment, the summations are pruned to exclude summations that would result in invalid combinations of the encoding coefficients (C.sub.0-C.sub.M-1). In an embodiment, substantially the same hardware is utilized for processing in-phase and quadrature phase components of the data word (X.sub.0-X.sub.M-1). In an embodiment, the coefficients (C.sub.0-C.sub.M-1) represent real numbers. In an alternative embodiment, the coefficients (C.sub.0-C.sub.M-1) represent complex numbers. In an embodiment, the coefficients (C.sub.0-C.sub.M-1) are represented with a single bit. Alternatively, the coefficients (C.sub.0-C.sub.M-1) are represented with multiple bits (e.g., magnitude). In an embodiment, the coefficients (C.sub.0-C.sub.M-1) represent a cyclic code keying ('CCK') code set substantially in accordance with IEEE 802.11 WLAN standard.

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First Claim