Decoding apparatus and method

A method of decoding data represented in a sequence of received symbols, wherein the sequence of received symbols comprises a source sequence of symbols and a first and a second sequence of codewords comprising:

• (a) receiving the sequence of received symbols from a medium;
• (b) grouping each of the source sequence of symbols, the first sequence of codewords and the second sequence of codewords into a number of blocks;
• (c) interleaving the source sequence of symbols using intra-block permutations on the source sequence of symbols and inter-block permutations on each intra-block permuted block across a predetermined number of the intra-block permuted blocks to produce a sequence of decoder interleaved symbols;
• (d) decoding the first sequence of codewords in combination with the source sequence of symbols to produce a sequence of primary decoded symbols;
• (e) interleaving the sequence of primary decoded symbols using intra-block permutations on the sequence of primary decoded symbols and inter-block permutations on each intra-block permuted block across a predetermined number of the intra-block permuted blocks to produce a sequence of intermediate symbols;
• (f) decoding the second sequence of codewords in combination with the sequence of decoder interleaved symbols and the sequence of intermediate symbols to produce a sequence of secondary decoded symbols;
• (g) de-interleaving the sequence of the secondary decoded symbols to produce a sequence of estimated symbols, and
• repeating steps (d), (e), (f) and (g) a total of N times, wherein
• the sequence of estimated symbols from step (g) is combined with the first sequence of codewords and the source sequence of symbols in step (d) on each successive repetition of the steps (d), (e), (f) and (g), the sequence of estimated symbols following the Nth repetition being the decoder output symbols, the output symbols not being combined with the first sequence of codewords and the source sequence of symbols.