Check-Irregular LDPC Codes for Unequal Error Protection under Iterative Decoding

Inhalt:
In many optimization techniques of LDPC codes, the check node irregularity is usually considered as being fixed because the profile must contain only two consecutive degrees in order to maximize the overall convergence speed of the code. We show in this paper that it is possible to construct bit-regular codes with more than two different degrees at check nodes side to speed up the convergence of some parts of the codeword, even if we may decrease a little the global convergence. Then, we take advantage of the check irregularity to create unequal error protection (UEP) codes, and present a very flexible method to achieve it. This method is based on pruning a mother code, thereby creating different subcodes with different UEP properties, but decoded with the same decoder.