Concatenated error correcting codes

1 . A method, comprising:

reading bits of a Low-Density Parity-Check (LDPC) codeword from a non-volatile storage device, the LDPC codeword being generated by LDPC encoding a Bose-Chaudhuri-Hocquenghem (BCH) codeword, the BCH codeword being generated by BCH encoding a data unit;

feeding the bits of the LDPC codeword read from the non-volatile storage device to an LDPC decoder; and

performing an iterative concatenated decoding process on the LDPC codeword in an iterative LDPC decoding process;

wherein performing the iterative concatenated decoding process comprises performing a first iteration comprising:

performing a first LDPC decoding iteration of the iterative LDPC decoding process on the LDPC codeword to generate a first intermediate LDPC decoding result;

determining a first LDPC syndrome of the first intermediate LDPC decoding result has not reached zero;

determining whether a triggering condition for BCH decoding is met using a BCH scheduler, wherein the triggering condition for BCH decoding is based on status information of the iterative LDPC decoding process;

in response to the triggering condition for BCH decoding being met, performing a BCH decoding process on the first intermediate LDPC decoding result;

in response to the triggering condition for BCH decoding not being met, performing a second iteration in the iterative concatenated decoding process;

wherein the second iteration starts with performing a second LDPC decoding iteration of the iterative LDPC decoding process on the LDPC codeword to generate a second intermediate LDPC decoding result;

wherein the second iteration continues by:

determining a second LDPC syndrome of the second intermediate LDPC decoding result has not reached zero;

determining whether the triggering condition for BCH decoding is met using the BCH scheduler;

in response to the triggering condition for BCH decoding being met, performing the BCH decoding process on the second intermediate LDPC decoding result;

in response to the triggering condition for BCH decoding not being met, performing a third iteration in the iterative concatenated decoding process;

wherein the third iteration starts with performing a third LDPC decoding iteration of the iterative LDPC decoding process on the LDPC codeword to generate a third intermediate LDPC decoding result.

2 . The method of claim 1 , further comprising:

in response to the triggering condition for BCH decoding being met, determining whether the BCH decoding process successfully decodes the BCH codeword;

in response to the BCH decoding process not successfully decoding the BCH codeword, performing the second iteration.

3 . The method of claim 1 , wherein the triggering condition for BCH decoding is that a number of flipped bits in the LDPC decoding iteration is zero and the LDPC syndrome is larger than zero.

4 . The method of claim 1 , wherein the triggering condition for BCH decoding is that the LDPC syndrome is smaller than a predefined threshold.

5 . The method of claim 1 , wherein the triggering condition for BCH decoding is that a number of flipped bits in the LDPC decoding iteration and a number of flipped bits in a previous LDPC decoding iteration are both smaller than a threshold.

6 . The method of claim 1 , wherein the triggering condition for BCH decoding is that a current iteration number has reached a predefined threshold.

7 . The method of claim 1 , wherein inputs to the BCH scheduler include one or more of: an LDPC iteration number, an LDPC column index, an LDPC layer index, the LDPC syndrome, a number of flipped bits in the LDPC decoding iteration, and a number of flipped bits in a previous LDPC decoding iteration.

8 . The method of claim 1 , wherein the iterative LDPC decoding process is a hard decision decoding process or a soft decision decoding process.