National Semiconductor Corporation

Philips Electronics North America Corporation

Hari Thirumoorthy

Samir N Hulyalkar

Sreen A Raghavan

Karl R Wittig

A Nearest Neighbors Look-Ahead Maximum Likelihood Estimation Sequence (LA-MLSE) algorithm for decoding data in a digital communications system forms the following three vectors to decode data: (1) a vector of the encoder input bit signals A&equals;A&lcub;k, k&plus;1, k&plus;2&rcub;, (2) a vector of the noise-free encoder channel output signals Y&equals;Y&lcub;A(k), A(k&plus;1), A(k&plus;2)&rcub;; and (3) a vector of the received signals R&equals;R(A(k), A(k&plus;1), A(k&plus;2)). If the distance between the received signal R and at least one of the channel output vectors which are of the form Y&lcub;1, A(k&plus;1), A(k&plus;2)&rcub; is shorter than the distance between the received signal R and the Nearest Neighbor of the signal Y&lcub;1, A(k&plus;1), A(k&plus;2)&rcub;, then A(k) is decoded as 1. In an All Neighbors Look-Ahead MLSE algorithm, A(k) is decoded as 1 only if the distance between the received signal R and at least one of the channel output vectors which are of the form Y&lcub;1, A(k&plus;1), A(k&plus;2)&rcub; is shorter than all the distances between signal R and each of the channel output vectors which are of the form Y&lcub;0, A(k&plus;1), A(k&plus;2)&rcub;. In a Nearest Neighbor Adjusted Depth Look-Ahead MLSE algorithm, if the distance obtained using the first two time indices, i.e. k and k&plus;1, is greater than a minimum distance, the time index k&plus;2 is omitted from the calculations, thereby reducing the amount of computations necessary to estimate the value of the encoder input data.

Look-ahead maximum likelihood sequence estimation decoder

An error computation processor for use in a Reed Solomon decoder for computing the error locations and magnitudes of a large data block having a maximum of t errors over a desired Galois field. The processor can compute the error-locator polynomial, the error-evaluator polynomial, and the values of the errors whose location was determined to be in error with only two polynomial storage registers, two element storage registers, one multiplier for performing selected multiplication and division, one adder for performing selected addition and subtraction, one error locator stack, one error value stack, and a syndrome register for storing the syndromes of the large data block.

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Hari Thirumoorthy