A method is provided for updating a check node in a low density parity check (LDPC) decoder, including: transmitting log-likelihood ratio (LLR) messages from variable nodes to a plurality of check nodes; decomposing the LLR messages in a plurality of node messages for each check node; and updating each check node using a modified function g(x), which is a function g′(x) comprising a sum operation of exponential functions based on the node messages.