On LDPC codes satisfying the (0, k) constraint

In this paper, we use the stochastic expectation-maximization method to illustrate how to come close to achieving the capacity of the noisy (0, k) constrained AWGN channels. We use the bit-flipping based constrained coding system proposed by Vasic to transmit (0, k) constrained LDPC codewords over an AWGN channel. In the original approach of Vasic, if the number of flipped bits is large, the message-passing decoder of LDPC codes fails to correct all the errors and the system is prone to an error floor even at high SNR values [Vasic, B et al., 2003]. We propose a flip decoder that exploits the information from the message-passing decoder to correct the flipped bits. We illustrate that the message-passing decoder and the flip decoder together correct both the channel and flip errors, and achieve rates close to the noisy (0, k) channel capacity.