Cyclic decoding for cascaded forward error-correction FEC codes
A computer implemented method for a cyclic (forward-backward) decoding for a forward error-correction FEC scheme includes decoding a given k−1 th codeword in a block code of length N in an optical communication system, forwarding M symbols' enhanced log likelihood ratios LLRs produced by decoding the k−1 th codeword, decoding the kth codeword together with forwarded M symbols' enhanced LLRS, and feeding backward, to the initial step i) decoding, corresponding overlapped M symbols' enhanced LLRs for decoding of the k−1th codeword again.
1. A computer implemented method for decoding cascaded forward error-correction FEC codes in an optical communication system, the method comprising the steps of:
i) decoding a given k−1 th codeword in a block code of length N in an optical communication system, k−1 th representing a sequence of a plurality of the codeword, N representing a length of the codeword;
ii) forwarding M symbols' enhanced log likelihood ratios LLRs produced by decoding the k−1 th codeword, M representing a number of the symbols produced by decoding a k−1 th codeword;
iii) decoding the kth codeword together with forwarded M symbols' enhanced LLRS, kth representing a particular codeword in the sequence of a plurality of the codeword; and
iv) feeding backward, to the initial step i) decoding, corresponding overlapped M symbols' enhanced LLRs for decoding of the k−1th codeword again.
2. The method of claim 1 , wherein the feeding backward step iv) enables decoding to be performed cyclically between two neighboring codes.
3. The method of claim 1 , wherein the cyclic decoding steps i)-iv) are carried out responsive to a cascaded soft-decision FEC decoding in parallel with a cascaded hard decision FEC decoding.
4. The method of claim 1 , wherein the cyclic decoding steps i)-iv) are carried out responsive to a cascaded hard decision FEC decoding.
5. The method of claim 1 , wherein the cyclic decoding steps i)-iv) utilize sharing of common decoding information LLRS between two continuous codewords.
6. The method of claim 1 , wherein the decoding steps i)-iv) enable a forward decoding process and a backward decoding process.
7. A system for a computer implemented method for decoding cascaded forward error-correction FEC codes in an optical communication system, the method comprising the steps of:
a first decoder for decoding a given k−1 th codeword in a block code of length N in an optical communication system, k−1 th representing a sequence of a plurality of the codeword, N representing a length of the codeword;
a feed forward processor for forwarding M symbols' enhanced log likelihood ratios LLRs produced by decoding the k−1 th codeword, M representing a number of the symbols produced by decoding a k−1 th codeword;
a second decoder for decoding the kth codeword together with forwarded M symbols' enhanced LLRS, kth representing a particular codeword in the plurality of the codeword; and
a feedback path for feeding backward, to the initial step i) decoding, corresponding overlapped M symbols' enhanced LLRs for decoding of the k−1th codeword again.
8. The system of claim 7 , wherein the feed forward processor enables decoding to be performed cyclically between two neighboring codes.
9. The system of claim 7 , wherein the first decoder, feed forward processor, second decoder and feedback path are operable in response to a cascaded soft-decision FEC decoding in parallel with a cascaded hard decision FEC decoding.
10. The system of claim 7 , wherein the first decoder, feed forward processor, second decoder and feedback path are operable in response to a cascaded soft decision FEC decoding.
11. The system of claim 7 , wherein the first decoder, feed forward processor, second decoder and feedback path are operable to utilize sharing of common decoding information LLRS between two continuous codewords.