A Class of Hybrid Coupled Parallel Concatenated Codes

It has been shown that, with equal decoding latency, the spatially coupled parallel concatenated codes (SC-PCC) perform worse than the uncoupled PCC. Based on this observation, this paper is intended to construct high-performance SC-PCC. Particularly, we propose a class of hybrid coupled parallel concatenated codes (HC-PCC), in which coupling is achieved by taking a portion of the systematic and parity bits of the current lower encoder as the inputs of its neighbouring lower encoders. The exact density evolution (DE) equations of the HC-PCC over the binary erasure channel (BEC) are derived and used to guide the construction of the HC-PCC. The DE analytical results show that the proposed HC-PCC admit better iterative decoding thresholds than those of the existing SC-PCC and the partially parity coupled turbo codes (PPC-TC). Particularly, with the systematic and the parity coupling memories both being equal to one, the decoding threshold of the rate-1/2 HC-PCC shows a gap of 0.0007 to the BEC capacity. Simulation results over the additive white Gaussian noise (AWGN) channels are also presented.