Lowering the error floor of short to medium length LDPC codes using optimal low correlated edge density (OED) PEG Tanner graphs
We propose a simple modification to the progressive edge growth (PEG) algorithm in order to control the girth of low density parity check (LDPC) code Tanner graphs constructed. Using the modified algorithm, the edge densities in short irregular rate LDPC code graphs can be increased without increasing the correlation between edges in graphs by creating cycles of undesired length. Density evolution (DE) optimized symbol node degree distributions used for constructing short to medium length codes were further optimized (slightly altered) while maintaining the maximum edge correlation (minimum local girths) that exists in graphs constructed using the unaltered DE optimized distributions. As a result of improved degree sequences (and graph densities) which were derived, short to medium length LDPC codes with lower error floors than published for LDPC codes of identical length and rate were found. These slightly denser codes have lower error floor than codes constructed using DE optimized degree distributions in PEG algorithms modified for improved approximate cycle extrinsic message degrees (ACE) Simulation results show that, at a code length of 512, efficient irregular rate PEG codes have significantly lower error floors than a rate IEEE 802.16e (WiMAX) LDPC code of length 576.
2016 24th International Conference on Software, Telecommunications and Computer Networks (SoftCOM)