This paper analyzes construction algorithms for low-density parity-check (LDPC) codes with respect to their unequal error protection (UEP) capabilities. We show that the choice of code construction algorithm highly affects the performance and UEP properties of LDPC codes with identical degree distributions. Our results provide an explanation to disagreements in earlier research.

This paper presents a strategy for the design of bandwidth-efficient LDPC codes with unequal error protection. Bandwidth efficiency is obtained by appropriately designing the codes for higher order constellations, assuming an AWGN channel. The irregularities of the LDPC code are designed, using the Gaussian approximation of the density evolution, to enhance the unequal error protection property of the code as well as account for the different bit error probabilities given by the higher order constellation. The proposed code design algorithm is flexible in terms of the number and proportions of protection classes. It also allows arbitrary modulation schemes. Our method combines the design of unequal error protection LDPC codes for the binary input AWGN channel with the code design for higher order constellations by dividing the variable node degree distribution into sub-degree distributions for each protection class and each level of protection from the modulation. The results show that appropriate code design for higher order constellations reduces the overall bit-error rate significantly. Furthermore, the unequal error protection capability of the code is increased, especially for high SNR.

This paper presents the design of multilevel coding schemes optimized for the transport of multimedia data. The key feature is unequal error protection which allows for more protection for header information and essential data, accepting worse performance for less important payload. The approach is based on the information theoretical description of mutual information in multilevel coding schemes. We discuss the suitability and UEP capability of standard as well as non-uniform signal constellations. We investigate the flexibility of this method regarding the design freedom and verify the approach by an image transmission application.

We present an optimization method for unequal error protection (UEP)-LDPC codes with higher order constellations. By modifying the density evolution algorithm under the Gaussian approximation, we propose a flexible code design algorithm for a variable number of protection classes and arbitrary modulation schemes with Gray mapping. Our results show that appropriate code design for higher order constellations reduces the overall bit-error rate. Furthermore, the influence on the UEP capability of the code, that is, the difference in bit-error rate between the protection classes, is investigated.

This paper describes the turbo decoding of hybrid concatenated codes with interleavers and presents a new analysis of the decoding process including information processing and convergence. From this analysis, the decoding can be scheduled with respect to optimization issues like computational complexity and convergence behavior