New constructions of variable-rate QC-LDPC codes by adding column-blocks or removing row-blocks

In this paper, new constructions of variable-rate quasi-cyclic low-density parity-check (QC-LDPC) codes are proposed. The criteria which guarantee that a higher-rate QC-LDPC code can be obtained by adding column-blocks to or removing row-blocks from the parity-check matrix of a given lower-rate QC-LDPC code are derived. Based on these criteria, new families of variable-rate QC-LDPC codes can be constructed. Simulation results show that the constructed codes provide a variety of error-protection capabilities against different channel conditions.