LINEAR BLOCK DECODER USING ROM

 LINEAR BLOCK DECODER USING ROM

A block diagram of a method for decoding a received signal is shown in Fig.2.3 Since H is fixed and known, the syndrome corresponding to any R can be stored in a ROM, the syndrome calculator. This syndrome is stored at a memory location whose address is arranged to be R itself. Hence when R appears at the address inputs of the ROM the syndrome is read out. The syndrome has n-k bits. Corresponding to each syndrome we shall have to determine the most likely error pattern. The error pattern, so determined for each syndrome, will he stored in the error-pattern generator ROM at an address which is arranged to be the same as the syndrome. If there is an error in a bit, say R_i , the corresponding error bit E_i will be E_i =1 and the output will be R_i* (where * denotes the complement) as required. The complexity of a decoder grows with increasing codeword size n.