Decoder for iterative decoding of binary cyclic codes

A decoder for decoding a data stream transmitted across a noisy channel into estimated bits, the data stream being encoded according to a cyclic code into a plurality of code words in sequence, the decoder comprising:

• input means for receiving input of a vector of noisy received values r(i) (where 0≦i≦n−1) of the data stream, a code length n of the code words, and a parity-check polynomial h(x) corresponding to the cyclic code, the parity-check polynomial h(x) having J-number of nonzero coefficients;
• a scaler for multiplying each noisy received value r(i) by a constant, and outputting each product as a log-likelihood ratio LLR(i);
• a Z processor for:
• receiving n-sets of πz(i,j) metrics (where 0≦j≦J−1), each set including J-number of πz(i,j) metrics;
• and
• calculating n-sets of λz(i,j) metrics based on the πz(i,j) metrics, each set including J-number of λz(i,j) metrics;
• an X processor for:
• receiving n-sets of λx(i,j) metrics, each set including J-number of λx(i,j) metrics,
• calculating n-number of a-posteriori values q(i) based on the λx(i,j) metrics and the log-likelihood ratios LLR(i);
• calculating n-sets of πx(i,j) metrics based on the λx(i,j) metrics and the a-posteriori values q(i), each set including J-number of πx(i,j) metrics;
• and
• determining n-number of estimated code bits i based on the a-posteriori values q(i);
• and
• an information exchange control unit for:
• distributing the πx(i,j) metrics based on a cyclic shift of the parity-check polynomial h(x) to produce the πz(i,j) metrics;
• and
• distributing the λz(i,j) metrics based on a reverse order of the cyclic shift of the parity-check polynomial h(x) to produce the λx(i,j) metrics.