Overlapped Circular SC-LDPC Codes and Their Modified Coupled Codes.

In this paper, overlapped circular spatially coupled low-density parity-check codes (OC-LDPC) are proposed and their modified coupled codes are derived, which show more improved performance compared with the spatially coupled low-density parity-check (SC-LDPC) codes. It is known that the SC-LDPC codes show asymptotically good performance when the chain length is sufficiently large. However, a large chain length requires a large number of iterations for decoding, which is often ignored in asymptotic analysis but it causes large decoding complexity in the decoding process. The proposed OC-LDPC codes reduce the decoding complexity while maintaining good asymptotic properties of the SC-LDPC codes. The improvement in the decoding complexity comes from that the proposed code is split into two SC-LDPC codes with shorter chain length during the decoding process. Thus, the OC-LDPC code can be decoded with lower iteration numbers required for decoding of two splitted SC-LDPC codes. Also, we design finite-length protograph-based codes for the proposed codes and it is shown that the proposed codes have superior finite-length code performances than the SC-LDPC codes.