| 摘要 |
Quasi-cyclic LDPC (Low Density Parity Check) code construction is presented that ensures no four cycles therein (e.g., in the bipartite graphs corresponding to the LDPC codes). Each LDPC code has a corresponding LDPC matrix that is composed of square sub-matrices, and based on the size of the sub-matrices of a particular LDPC matrix, then sub-matrix-based cyclic shifting is performed as not only a function of sub-matrix size, but also the row and column indices, to generate CSI (Cyclic Shifted Identity) sub-matrices. When the sub-matrix size is prime (e.g., each sub-matrix being size q×q, where q is a prime number), then it is guaranteed that no four cycles will exist in the resulting bipartite graph corresponding to the LDPC code of that LDPC matrix. When q is a non-prime number, an avoidance set can be used and/or one or more sub-matrices can be made to be an all zero-valued sub-matrix. |
