The Single Parity Check Code in Concatenation with Non-Recursive Inner Convolutional Codes

For serially concatenated codes, the general conception has been that one should only use recursive convolutional codes as inner codes. The reason for this is that non-recursive inner codes have error events of input distance one, that induces an irreducible error floor. However, as we show in this paper, this problem can largely be overcome by minimizing the role of input distance one error events for non-recursive inner convolutional codes. The system we consider is iteratively decoded serially concatenated trellis coded modulation (SCTCM) where the outer code is a single parity check code and the inner code is a two-state rate 3/4 non-recursive convolutional code whose output is mapped to 8PSK. Simulation results are obtained for the additive white Gaussian noise (AWGN) channel