Enhanced turbo product code decorder system

Abstract

A method and apparatus for decoding a linear block encoded string of information bits comprising: converting the string into a plurality of codewords. Performing hard and soft decisions on each codeword to generate a hard and soft decision vector. Computing the syndrome and finding the location of the two minimum values by Galois Field Arithmetic. Designating these values LOW 1 and LOW 2 and xoring with a Nc 1, thus generating Nc 2. Swapping Nc 1 with Nc 2 and determining the lowest soft decision value, Min 1 and a next lowest value, Min 2. The two bit locations creating Min 1 are designated as MinA and MinB. MinA being replaced with Min 2 minus the value MinA. MinB being replaced with Min 2 minus the value at MinB. Generating an output codeword by subtracting Min 1 from all other bit locations values and 2's complementing all soft values with 0 in their location. Creating the new soft value vector.

What is claimed is:  
     
         1 . A method for decoding a linear block encoded string of information bits comprising the steps of: 
 a. converting the string of information bits into a plurality of codewords, wherein each codewords has a length N;    b. performing hard and soft decisions on each codeword in order to generate a hard decision vector h of length N and a soft decision vector c of length N;    c. computing the syndrome of the hard decision vector h by using Galois Field Arithmetic;    d. finding the location of the two minimum values in the soft decision vector by the Galois Field Arithmetic and designating these locations as LOW 1  and LOW 2 ,    e. xoring the LOW 1  and LOW 2  with a Nc 1  bit locations, wherein a Nc 2  bit location is generated    f. swapping the soft decision value at location Nc 1  with the soft decision value at location Nc 2  for each nearby valid codewords computed;    g. determining which soft decision value sum is the lowest and designate this as Min 1 ;    h. designating two bit locations which created Min 1  as MinA and MinB;    i. designating the next lowest soft value sum as Min 2 ;    j. replacing the value at bit location MinA with the value of min 2  minus the current value at bit location MinA,    k. replacing the value at bit location MinB in the soft decision vector with the value of min 2  minus the current value at bit location MinB;    l. subtracting the value of mini from the values in all other bit locations in the soft decision vector in order to generate an output codeword; and    m. 2's complementing all soft values in the output codeword at bit locations which correspond with bit locations in the hard decision vector having a 0 in their location and creating the new signed soft value vector.