The present disclosure relates to a decoding method. The decoding method includes a sequentially determining series of source bits from a codeword by performing a first decoding operation and a second decoding operation. For instance, a series of N source bits may be divided into a first bit group of X source bits and a second bit group of Y source bits. The initial X source bits are sequentially determined in the first decoding operation and the remaining Y source bits are sequentially determined in the second decoding operation. The first decoding operation includes sorting at least 2L reliability values, which are calculated from L bit sequences, where L is an integer greater than 0. The second decoding operation includes determining a source bit in each of the L bit sequences, based on the at least 2L reliability values.