A communication system includes a transmitter having an encoder configured to encode input data using FEC codewords and a receiver including a decoder configured to decode the FEC codewords using a parity check matrix. The decoder includes check node processing units each configured to perform a check node computation on an FEC codeword using a different row of the parity check matrix. Each of the check node processing units includes an input computation stage configured to compute initial computation values, a pipelined message memory configured to shift the initial computation values at a predefined clock interval, an output computation stage configured to generate a plurality of check node output messages, a plurality of variable node processing units each configured to perform variable node update computations to generate the variable node messages, and an output circuit configured to generate a decoded codeword based on the variable node messages.