Disclosed are a controller, a system and a method for decoding LDPC codewords based on historical decoding information. In a decoding iteration, the value of flipping energy of a variable node in a codeword is computed based on information representing decoding of the codeword before the decoding iteration. A comparison result is obtained by comparing the value of flipping energy to a flipping energy threshold. And the variable node is flipped in response to the comparison result satisfying a criterion. A controller with a process configured to implement the BF decoding process, as well as a system with the controller.

A method, system, and ASIC chip for comparing a bit error rate (BER) to a forward error correction (FEC) threshold to determine a Q margin for a codeblock; wherein the BER corresponds to the number of errors in a given amount of data; where a codeblock of a FEC corresponds to the given amount of data; wherein the FEC threshold corresponds to the maximum amount of errors per codeblock that the FEC is able to remove per given amount of data; wherein the Q margin corresponds to a difference between the BER and the FEC threshold.

A method, system, and ASIC chip for comparing a bit error rate (BER) to a forward error correction (FEC) threshold to determine a Q margin for a codeblock; wherein the BER corresponds to the number of errors in a given amount of data; where a codeblock of a FEC corresponds to the given amount of data; wherein the FEC threshold corresponds to the maximum amount of errors per codeblock that the FEC is able to remove per given amount of data; wherein the Q margin corresponds to a difference between the BER and the FEC threshold.

Layered decoding of low-density parity check (LDPC) codes are decoded by selecting one or more of a plurality of check nodes (CNs) based on degree in priority, where the degree in priority for each of the plurality of CNs is based on a number of variable nodes (VNs) connected to the respective CN. Layered decoding for an LDPC code is performed based on applying a sum-product algorithm and an approximated sum-product algorithm. The sum-product algorithm is applied to at least some of the selected one or more CNs among the plurality of CNs. The approximated sum-product algorithm is applied to one or more remaining CNs, other than the selected one or more CNs, among the plurality of CNs.

Layered decoding of low-density parity check (LDPC) codes are decoded by selecting one or more of a plurality of check nodes (CNs) based on degree in priority, where the degree in priority for each of the plurality of CNs is based on a number of variable nodes (VNs) connected to the respective CN. Layered decoding for an LDPC code is performed based on applying a sum-product algorithm and an approximated sum-product algorithm. The sum-product algorithm is applied to at least some of the selected one or more CNs among the plurality of CNs. The approximated sum-product algorithm is applied to one or more remaining CNs, other than the selected one or more CNs, among the plurality of CNs.