Performance under delay constraints on iterative decoding of LDPC codes

The performance of a system with a quasi-cyclic low-density parity-check code is examined under various constraints on the decoding delay. Two alternatives are considered for the message-passing decoding algorithm: the sum-product algorithm and the turbo-decoding message-passing algorithm. It is shown that their relative performance depends heavily on the stringency of the delay constraint; the TDMP algorithm results in substantially better performance than the SPA if the constraint is stringent.