Effect of the threshold offset on the performance of UEP LDPC codes

This letter addresses the effect of threshold offset on the average performance and UEP capability of higher order constellation (HOC) unequal error protection low density parity check (UEP-LDPC) codes. We optimize the variable node degree distribution for an HOC UEP-LDPC code at a minimum threshold, with a fixed check node degree distribution and code rate. The average performance and the UEP capability of the ensemble code for a marginal offset in the threshold value were investigated. The simulation results show that the average performance and UEP capability can be enhanced by a slight offset in the threshold value. We looked into the connectivity between protection classes due to the threshold offset for a possible answer to the performance gain.