Multiple codeword interleaver method and apparatus

Abstract

An interleaver which allows the use of consecutive groups of codewords within a frame, where the maximum size of each codeword is constrained to be equal to or less than a certain maximum size. In accordance with required performance standards, i.e., the specification of a maximum number of data errors that the system is supposed to withstand, the interleaver is capable of limiting the number of errors which occur within a specific codeword to be less than the maximum number of errors that can be corrected by the particular coding scheme. The interleaver is able to achieve this result even for codewords of uneven length. The interleaver attempts to divide the total number of symbols to be transmitted in a frame into equal size codewords. If the codeword size cannot be made equal, then unequal size codewords are used, however, the difference in size between codewords cannot be greater than one symbol. The R dimension of the interleaver memory is then generally determined based on the largest codeword size, except with certain modifications. Based on whether the codeword lengths are even, odd or a mix of even odd, a variable number of 'dummy' symbols is inserted into the codewords to maintain the R and C dimensions of the interleaver memory such that R and C do not have any common multiple factors. A de-interleaver may also be realized by essentially performing the reverse process as the interleaver.