关键词: 仿射置换矩阵, 空间耦合LDPC码, 环分布, 瀑布区, 错误平层

Abstract: Spatially-coupled (SC) low density parity check (LDPC) code is a kind of LDPC code with convolution structure. This structure not only brings convolution gain but also introduces memory structure. For codes using sliding window decoding, the previous error message will affect the subsequent decoding, especially for SC-LDPC codes with long coupling length, which is easy to cause error propagation. Therefore, SC-LDPC codes have stricter requirements for structural design than traditional LDPC block codes. To improve the design space and performance of SC-LDPC codes, an affine permutation matrix (APM) is proposed to replace the traditional cyclic permutation matrix for code construction. The full cycles and non-full cycles phenomena in APM-LDPC code's structures are discovered and demonstrated, and the non-full cycles phenomenon only occurs in APM-LDPC code is proved. The APM-SC-LDPC code with non-full cycles phenomenon can significantly reduce the number of short cycles, the error-floor and significantly improve in waterfall region.

Key words: affine permutation matrix, spatially coupled low density parity check code, cycles distribution, waterfall region, error floor